C8051F39x/37x 50 MIPS 16 kB Flash, 512B EEPROM Mixed-Signal MCU Analog Peripherals (‘F390/2/4/6/8 and ‘F370/4) High-Speed 8051µC Core - 10-Bit ADC - Pipelined instruction architecture; executes 70% of • Programmable throughput up to 500ksps instructions in 1 or 2system clocks • Up to 16 external inputs, programmable as single- - Up to 50MIPS throughput with 50MHz clock ended or differential - Expanded interrupt handler • Reference from on-chip voltage reference, V or DD Memory external VREF pin • Internal or external start of conversion sources - Up to 1kB internal data RAM (256 + 768) - Two 10-Bit Current Output DACs - Up to 16kB Flash; In-system programmable in 512- • Supports output through resets for continuous byte Sectors operation - 512 bytes of byte-programmable EEPROM; 1 mil- - Comparator • Programmable hysteresis and response time lion write/erase cycles (‘F37x) • Configurable as interrupt or reset source Digital Peripherals - Precision Temperature Sensor - 21 or 17 Port I/O • Accurate to ±2°C across temperature range with no - UART, 2 SMBus (I2C compatible), and SPI serial user calibration ports On-Chip Debug - Six general purpose 16-bit counter/timers - On-chip debug circuitry facilitates full speed, non- intrusive in-system debug (no emulator required) - 16-Bit programmable counter array (PCA) with three capture/compare modules and PWM functionality - Provides breakpoints, single stepping, Clock Sources inspect/modify memory and registers Low Power - 49MHz ±2% precision internal oscillator - 160µA/MHz Active mode with 49MHz internal • Supports crystal-less UART operation precision oscillator • Low-power suspend mode with fast wake time - 80kHz low-frequency, low-power oscillator - 200nA Stop mode current - External oscillator: Crystal, RC, C, or CMOS clock Temperature Range - –40 to +85°C (‘F37x) - Can switch between clock sources on-the-fly; useful in power saving modes - –40 to +105°C (‘F39x) Supply Voltage 1.8 to 3.6V Package - Built-in voltage supply monitor - 24-Pin QFN (‘F390/1/4/5 and ‘F37x) - 20-Pin QFN (‘F392/3/6/7/8/9) ANALOG DIGITAL I/O PERIPHERALS UART SMBus0 Port 0 A 10-bit 10-bit SMBus1 MU 500 ksps CuDrCrAeu1nrC0rt-e bnitt PSCPAI0 BAR Port 1 X ADC DAC PCA1 S PCA2 S O Timer 0 R P2.0 VREF Temp Sensor Timer 1 C + Precision Timer 2 P2.1– – Temp Sensor Timer 3 P2.4* Timer 4 VOLTAGE ‘F390/2/4/6/8 & COMPARATOR ‘F370/4 Only Timer 5 *P2.1–2.4 QFN24 Only 49 MHz PRECISION 80 KHz LOW FREQUENCY 512 B INTERNAL OSCILLATOR INTERNAL OSCILLATOR EEPROM HIGH-SPEED CONTROLLER CORE 16/8 kB 8051 CPU 1024 B ISP FLASH (50 MIPS) SRAM FLEXIBLE DEBUG POR WDT INTERRUPTS CIRCUITRY Rev. 1.2 2/19 Copyright © 2019 by Silicon Laboratories C8051F39x/37x

C8051F39x/37x 2 Rev. 1.2

C8051F39x/37x 1. System Overview..................................................................................................... 17 2. Ordering Information............................................................................................... 20 3. C8051F33x Compatibility........................................................................................ 21 3.1. Hardware Incompatibilities................................................................................ 21 4. Pin Definitions.......................................................................................................... 22 5. QFN-20 Package Specifications............................................................................. 28 6. QFN-24 Package Specifications............................................................................. 30 7. Electrical Characteristics........................................................................................ 32 7.1. Absolute Maximum Specifications..................................................................... 32 7.2. Electrical Characteristics................................................................................... 33 7.3. Typical Performance Curves............................................................................. 45 8. Precision Temperature Sensor (C8051F390/2/4/6/8 and C8051F370/4 Only)............................................................... 47 8.1. Temperature in Two’s Complement.................................................................. 47 9. 10-Bit ADC (ADC0, C8051F390/2/4/6/8 and C8051F370/4 Only)........................... 50 9.1. Output Code Formatting.................................................................................... 51 9.2. Modes of Operation........................................................................................... 52 9.2.1. Starting a Conversion................................................................................ 52 9.2.2. Tracking Modes......................................................................................... 53 9.2.3. Settling Time Requirements...................................................................... 54 9.3. Programmable Window Detector....................................................................... 58 9.3.1. Window Detector Example........................................................................ 60 9.4. ADC0 Analog Multiplexer (C8051F390/2/4/6/8 and C8051F370/4 Only).......... 61 10. Temperature Sensor (C8051F390/2/4/6/8 and C8051F370/4 Only)..................... 64 10.1. Calibration....................................................................................................... 65 11. 10-Bit Current Mode DACs (IDA0, IDA1, C8051F390/2/4/6/8 and C8051F370/4 On- ly) ............................................................................................................................ 66 11.1. IDAC Output Scheduling................................................................................. 66 11.1.1. Update Output On-Demand.................................................................... 66 11.1.2. Update Output Based on Timer Overflow............................................... 68 11.1.3. Update Output Based on CNVSTR Edge............................................... 68 11.2. IDAC Reset Behavior...................................................................................... 68 11.3. IDAC Output Mapping..................................................................................... 68 12. Voltage Reference Options................................................................................... 73 13. Voltage Regulator.................................................................................................. 75 13.1. Power Modes................................................................................................... 75 14. Comparator0........................................................................................................... 76 14.1. Comparator Multiplexer................................................................................... 80 15. CIP-51 Microcontroller........................................................................................... 82 15.1. Instruction Set.................................................................................................. 83 15.1.1. Instruction and CPU Timing.................................................................... 83 15.2. CIP-51 Register Descriptions.......................................................................... 87 16. Prefetch Engine...................................................................................................... 92 17. Memory Organization............................................................................................ 93 17.1. Program Memory............................................................................................. 94 Rev. 1.2 3

C8051F39x/37x 17.1.1. MOVX Instruction and Program Memory................................................ 94 17.2. Data Memory................................................................................................... 94 17.2.1. Internal RAM........................................................................................... 94 17.2.1.1. General Purpose Registers............................................................ 95 17.2.1.2. Bit Addressable Locations.............................................................. 95 17.2.1.3. Stack ............................................................................................ 95 17.2.2. External RAM.......................................................................................... 95 18. Device ID Registers............................................................................................... 97 19. Special Function Registers................................................................................. 101 19.1. SFR Paging................................................................................................... 101 19.2. Interrupts and Automatic SFR Paging........................................................... 101 19.3. SFR Page Stack Example............................................................................. 103 20. Interrupts.............................................................................................................. 117 20.1. MCU Interrupt Sources and Vectors.............................................................. 118 20.1.1. Interrupt Priorities.................................................................................. 118 20.1.2. Interrupt Latency................................................................................... 118 20.2. Interrupt Register Descriptions...................................................................... 120 20.3. External Interrupts INT0 and INT1................................................................. 128 21. Flash Memory....................................................................................................... 131 21.1. Programming The Flash Memory.................................................................. 131 21.1.1. Flash Lock and Key Functions.............................................................. 131 21.1.2. Flash Erase Procedure......................................................................... 131 21.1.3. Flash Write Procedure.......................................................................... 132 21.2. Non-volatile Data Storage............................................................................. 132 21.3. Security Options............................................................................................ 133 21.4. Flash Write and Erase Guidelines................................................................. 135 21.4.1. V Maintenance and the V Monitor ................................................ 135 DD DD 21.4.2. PSWE Maintenance.............................................................................. 135 21.4.3. System Clock........................................................................................ 136 22. EEPROM (C8051F37x)......................................................................................... 140 22.1. EEPROM Communication Protocol.............................................................. 140 22.1.1. Slave Address Byte............................................................................... 141 22.1.2. Acknowledgement (ACK)...................................................................... 141 22.1.3. Not-Acknowledgement (NACK)............................................................. 141 22.1.4. Reset..................................................................................................... 141 22.2. Write Operation............................................................................................. 142 22.3. Read Operation............................................................................................. 143 22.3.1. Current Address Read.......................................................................... 143 22.3.2. Selective Address Read........................................................................ 145 23. Cyclic Redundancy Check Unit (CRC0)............................................................. 147 23.1. CRC Algorithm............................................................................................... 147 23.2. Preparing for a CRC Calculation................................................................... 149 23.3. Performing a CRC Calculation...................................................................... 149 23.4. Accessing the CRC0 Result.......................................................................... 149 23.5. CRC0 Bit Reverse Feature............................................................................ 149 4 Rev. 1.2

C8051F39x/37x 24. Reset Sources...................................................................................................... 155 24.1. Power-On Reset............................................................................................ 156 24.2. Power-Fail Reset / VDD Monitor................................................................... 157 24.3. External Reset............................................................................................... 159 24.4. Missing Clock Detector Reset....................................................................... 159 24.5. Comparator0 Reset....................................................................................... 159 24.6. PCA Watchdog Timer Reset......................................................................... 159 24.7. Flash Error Reset.......................................................................................... 159 24.8. Software Reset.............................................................................................. 159 25. Power Management Modes................................................................................. 161 25.1. Idle Mode....................................................................................................... 161 25.2. Stop Mode..................................................................................................... 162 25.3. Suspend Mode.............................................................................................. 162 26. Oscillators and Clock Selection......................................................................... 164 26.1. System Clock Selection................................................................................. 165 26.2. Programmable Internal High-Frequency (H-F) Oscillator.............................. 166 26.2.1. Internal Oscillator Suspend Mode......................................................... 166 26.3. Programmable Internal Low-Frequency (L-F) Oscillator............................... 168 26.3.1. Calibrating the Internal L-F Oscillator.................................................... 168 26.4. Internal Low-Power Oscillator........................................................................ 169 26.5. External Oscillator Drive Circuit..................................................................... 169 26.5.1. External Crystal Mode........................................................................... 169 26.5.2. External RC Example............................................................................ 171 26.5.3. External Capacitor Example.................................................................. 171 27. Port Input/Output................................................................................................. 173 27.1. Port I/O Modes of Operation.......................................................................... 174 27.1.1. Port Pins Configured for Analog I/O...................................................... 174 27.1.2. Port Pins Configured For Digital I/O...................................................... 174 27.2. Assigning Port I/O Pins to Analog and Digital Functions............................... 175 27.2.1. Assigning Port I/O Pins to Analog Functions........................................ 175 27.2.2. Assigning Port I/O Pins to Digital Functions.......................................... 176 27.2.3. Assigning Port I/O Pins to External Event Trigger Functions................ 177 27.3. Priority Crossbar Decoder............................................................................. 178 27.4. Port I/O Initialization...................................................................................... 180 27.5. Port Match..................................................................................................... 183 27.6. Special Function Registers for Accessing and Configuring Port I/O............. 185 28. SMBus0 and SMBus1 (I2C Compatible)............................................................. 192 28.1. Supporting Documents.................................................................................. 193 28.2. SMBus Configuration..................................................................................... 193 28.3. SMBus Operation.......................................................................................... 193 28.3.1. Transmitter vs. Receiver....................................................................... 194 28.3.2. Arbitration.............................................................................................. 194 28.3.3. Clock Low Extension............................................................................. 194 28.3.4. SCL Low Timeout.................................................................................. 194 28.3.5. SCL High (SMBus Free) Timeout......................................................... 195 Rev. 1.2 5

C8051F39x/37x 28.4. Using the SMBus........................................................................................... 195 28.4.1. SMBus Configuration Register.............................................................. 195 28.4.2. SMBus Pin Swap.................................................................................. 197 28.4.3. SMBus Timing Control.......................................................................... 197 28.4.4. SMBnCN Control Register.................................................................... 201 28.4.4.1. Software ACK Generation............................................................ 201 28.4.4.2. Hardware ACK Generation........................................................... 201 28.4.5. Hardware Slave Address Recognition.................................................. 204 28.4.6. Data Register........................................................................................ 209 28.5. SMBus Transfer Modes................................................................................. 211 28.5.1. Write Sequence (Master)...................................................................... 211 28.5.2. Read Sequence (Master)...................................................................... 212 28.5.3. Write Sequence (Slave)........................................................................ 213 28.5.4. Read Sequence (Slave)........................................................................ 214 28.6. SMBus Status Decoding................................................................................ 214 29. UART0................................................................................................................... 220 29.1. Enhanced Baud Rate Generation.................................................................. 221 29.2. Operational Modes........................................................................................ 222 29.2.1. 8-Bit UART............................................................................................ 222 29.2.2. 9-Bit UART............................................................................................ 223 29.3. Multiprocessor Communications................................................................... 224 30. Enhanced Serial Peripheral Interface (SPI0)..................................................... 228 30.1. Signal Descriptions........................................................................................ 229 30.1.1. Master Out, Slave In (MOSI)................................................................. 229 30.1.2. Master In, Slave Out (MISO)................................................................. 229 30.1.3. Serial Clock (SCK)................................................................................ 229 30.1.4. Slave Select (NSS)............................................................................... 229 30.2. SPI0 Master Mode Operation........................................................................ 230 30.3. SPI0 Slave Mode Operation.......................................................................... 231 30.4. SPI0 Interrupt Sources.................................................................................. 232 30.5. Serial Clock Phase and Polarity.................................................................... 232 30.6. SPI Special Function Registers..................................................................... 234 31. Timers................................................................................................................... 242 31.1. Timer 0 and Timer 1...................................................................................... 245 31.1.1. Mode 0: 13-bit Counter/Timer............................................................... 245 31.1.2. Mode 1: 16-bit Counter/Timer............................................................... 246 31.1.3. Mode 2: 8-bit Counter/Timer with Auto-Reload..................................... 247 31.1.4. Mode 3: Two 8-bit Counter/Timers (Timer 0 Only)................................ 248 31.2. Timer 2.......................................................................................................... 253 31.2.1. 16-bit Timer with Auto-Reload............................................................... 253 31.2.2. 8-bit Timers with Auto-Reload............................................................... 254 31.2.3. Low-Frequency Oscillator (LFO) Capture Mode................................... 255 31.3. Timer 3.......................................................................................................... 259 31.3.1. 16-bit Timer with Auto-Reload............................................................... 259 31.3.2. 8-bit Timers with Auto-Reload............................................................... 260 6 Rev. 1.2

C8051F39x/37x 31.3.3. Low-Frequency Oscillator (LFO) Capture Mode................................... 261 31.4. Timer 4.......................................................................................................... 265 31.4.1. 16-bit Timer with Auto-Reload............................................................... 265 31.4.2. 8-bit Timers with Auto-Reload............................................................... 266 31.5. Timer 5.......................................................................................................... 270 31.5.1. 16-bit Timer with Auto-Reload............................................................... 270 31.5.2. 8-bit Timers with Auto-Reload............................................................... 271 32. Programmable Counter Array............................................................................. 275 32.1. PCA Counter/Timer....................................................................................... 276 32.2. PCA0 Interrupt Sources................................................................................. 277 32.3. Capture/Compare Modules........................................................................... 278 32.3.1. Edge-triggered Capture Mode............................................................... 279 32.3.2. Software Timer (Compare) Mode.......................................................... 280 32.3.3. High-Speed Output Mode..................................................................... 281 32.3.4. Frequency Output Mode....................................................................... 282 32.3.5. 8-bit, 9-bit, 10-bit and 11-bit Pulse Width Modulator Modes................ 282 32.3.5.1. 8-bit Pulse Width Modulator Mode............................................... 283 32.3.5.2. 9/10/11-bit Pulse Width Modulator Mode..................................... 284 32.3.6. 16-Bit Pulse Width Modulator Mode..................................................... 285 32.4. Watchdog Timer Mode.................................................................................. 286 32.4.1. Watchdog Timer Operation................................................................... 286 32.4.2. Watchdog Timer Usage........................................................................ 287 32.5. Comparator Clear Function........................................................................... 288 32.6. Register Descriptions for PCA0..................................................................... 290 33. C2 Interface.......................................................................................................... 297 33.1. C2 Interface Registers................................................................................... 297 33.2. C2 Pin Sharing.............................................................................................. 300 Document Change List.............................................................................................. 301 Contact Information................................................................................................... 303 Rev. 1.2 7

C8051F39x/37x Figure 1.1. C8051F392/3/6/7/8/9 Block Diagram .................................................... 18 Figure 1.2. C8051F390/1/4/5 Block Diagram .......................................................... 18 Figure 1.3. C8051F370/1/4/5 Block Diagram .......................................................... 19 Figure 4.1. C8051F392/3/6/7/8/9 QFN-20 Pinout Diagram (Top View) ................... 25 Figure 4.2. C8051F390/1/4/5 Pinout Diagram (Top View) ...................................... 26 Figure 4.3. C8051F370/1/4/5 Pinout Diagram (Top View) ...................................... 27 Figure 5.1. QFN-20 Package Drawing .................................................................... 28 Figure 5.2. QFN-20 Recommended PCB Land Pattern .......................................... 29 Figure 6.1. QFN-24 Package Drawing .................................................................... 30 Figure 6.2. QFN-24 Recommended PCB Land Pattern .......................................... 31 Figure 7.1. Normal Mode Digital Supply Current vs. Frequency ............................. 45 Figure 7.2. Idle Mode Digital Supply Current vs. Frequency ................................... 45 Figure 7.3. Precision Temperature Sensor Error vs. Temperature ......................... 46 Figure 9.1. ADC0 Functional Block Diagram ........................................................... 50 Figure 9.2. 10-Bit ADC Track and Conversion Example Timing ............................. 53 Figure 9.3. ADC0 Equivalent Input Circuits ............................................................. 54 Figure 9.4. ADC Window Compare Example: Right-Justified, Single-Ended Data . 60 Figure 9.5. ADC Window Compare Example: Left-Justified, Single-Ended Data .... 60 Figure 9.6. ADC0 Multiplexer Block Diagram .......................................................... 61 Figure 10.1. Temperature Sensor Transfer Function .............................................. 64 Figure 10.2. Temperature Sensor Error with 1-Point Calibration at 0 °C ................ 65 Figure 11.1. IDA0 Functional Block Diagram .......................................................... 66 Figure 11.2. IDA1 Functional Block Diagram .......................................................... 67 Figure 11.3. IDA0 Data Word Mapping ................................................................... 68 Figure 12.1. Voltage Reference Functional Block Diagram ..................................... 73 Figure 14.1. Comparator0 Functional Block Diagram ............................................. 76 Figure 14.2. Comparator Hysteresis Plot ................................................................ 77 Figure 14.3. Comparator Input Multiplexer Block Diagram ...................................... 80 Figure 15.1. CIP-51 Block Diagram ......................................................................... 82 Figure 17.1. C8051F39x/37x Memory Map ............................................................. 93 Figure 17.2. Flash Program Memory Map ............................................................... 94 Figure 19.1. SFR Page Stack ................................................................................ 102 Figure 19.2. SFR Page Stack While Using SFR Page 0x0F To Access TS0CN .. 103 Figure 19.3. SFR Page Stack After SPI0 Interrupt Occurs .................................... 104 Figure 19.4. SFR Page Stack Upon PCA Interrupt Occurring During a SPI0 ISR 105 Figure 19.5. SFR Page Stack Upon Return from PCA0 Interrupt ......................... 106 Figure 19.6. SFR Page Stack Upon Return From SPI0 Interrupt .......................... 107 Figure 21.1. Security Byte Decoding ..................................................................... 133 Figure 22.1. Slave Address Byte Definition ........................................................... 141 Figure 22.2. Write Operation (Single Byte) ............................................................ 142 Figure 22.3. Write Operation (Multiple Bytes) ....................................................... 142 Figure 22.4. Current Address Read Operation (Single Byte) ................................ 143 Figure 22.5. Current Address Read Operation (Multiple Bytes) ............................ 144 Figure 22.6. Selective Address Read (Single Byte) .............................................. 145 Figure 22.7. Selective Address Read (Multiple Bytes) .......................................... 146 8 Rev. 1.2

C8051F39x/37x Figure 23.1. CRC0 Block Diagram ........................................................................ 147 Figure 23.2. Bit Reverse Register ......................................................................... 149 Figure 24.1. Reset Sources ................................................................................... 155 Figure 24.2. Power-On and VDD Monitor Reset Timing ....................................... 156 Figure 26.1. Oscillator Options .............................................................................. 164 Figure 26.2. External Crystal Example .................................................................. 170 Figure 27.1. Port I/O Functional Block Diagram .................................................... 173 Figure 27.2. Port I/O Cell Block Diagram .............................................................. 174 Figure 27.3. Crossbar Priority Decoder - Possible Pin Assignments .................... 178 Figure 27.4. Crossbar Priority Decoder Example .................................................. 179 Figure 28.1. SMBus0 Block Diagram .................................................................... 192 Figure 28.2. Typical SMBus Configuration ............................................................ 193 Figure 28.3. SMBus Transaction ........................................................................... 194 Figure 28.4. Typical SMBus SCL Generation ........................................................ 196 Figure 28.5. Typical Master Write Sequence ........................................................ 211 Figure 28.6. Typical Master Read Sequence ........................................................ 212 Figure 28.7. Typical Slave Write Sequence .......................................................... 213 Figure 28.8. Typical Slave Read Sequence .......................................................... 214 Figure 29.1. UART0 Block Diagram ...................................................................... 220 Figure 29.2. UART0 Baud Rate Logic ................................................................... 221 Figure 29.3. UART Interconnect Diagram ............................................................. 222 Figure 29.4. 8-Bit UART Timing Diagram .............................................................. 222 Figure 29.5. 9-Bit UART Timing Diagram .............................................................. 223 Figure 29.6. UART Multi-Processor Mode Interconnect Diagram ......................... 224 Figure 30.1. SPI Block Diagram ............................................................................ 228 Figure 30.2. Multiple-Master Mode Connection Diagram ...................................... 230 Figure 30.3. 3-Wire Single Master and 3-Wire Single Slave Mode Connection Diagram 231 Figure 30.4. 4-Wire Single Master Mode and 4-Wire Slave Mode Connection Diagram 231 Figure 30.5. Master Mode Data/Clock Timing ....................................................... 233 Figure 30.6. Slave Mode Data/Clock Timing (CKPHA = 0) ................................... 233 Figure 30.7. Slave Mode Data/Clock Timing (CKPHA = 1) ................................... 234 Figure 30.8. SPI Master Timing (CKPHA = 0) ....................................................... 238 Figure 30.9. SPI Master Timing (CKPHA = 1) ....................................................... 239 Figure 30.10. SPI Slave Timing (CKPHA = 0) ....................................................... 239 Figure 30.11. SPI Slave Timing (CKPHA = 1) ....................................................... 240 Figure 31.1. T0 Mode 0 Block Diagram ................................................................. 246 Figure 31.2. T0 Mode 2 Block Diagram ................................................................. 247 Figure 31.3. T0 Mode 3 Block Diagram ................................................................. 248 Figure 31.4. Timer 2 16-Bit Mode Block Diagram ................................................. 253 Figure 31.5. Timer 2 8-Bit Mode Block Diagram ................................................... 254 Figure 31.6. Timer 2 Low-Frequency Oscillation Capture Mode Block Diagram ... 255 Figure 31.7. Timer 3 16-Bit Mode Block Diagram ................................................. 259 Figure 31.8. Timer 3 8-Bit Mode Block Diagram ................................................... 260 Rev. 1.2 9

C8051F39x/37x Figure 31.9. Timer 3 Low-Frequency Oscillation Capture Mode Block Diagram ... 261 Figure 31.10. Timer 4 16-Bit Mode Block Diagram ............................................... 265 Figure 31.11. Timer 4 8-Bit Mode Block Diagram ................................................. 266 Figure 31.12. Timer 5 16-Bit Mode Block Diagram ............................................... 270 Figure 31.13. Timer 5 8-Bit Mode Block Diagram ................................................. 271 Figure 32.1. PCA Block Diagram ........................................................................... 275 Figure 32.2. PCA Counter/Timer Block Diagram ................................................... 276 Figure 32.3. PCA Interrupt Block Diagram ............................................................ 277 Figure 32.4. PCA Capture Mode Diagram ............................................................. 279 Figure 32.5. PCA Software Timer Mode Diagram ................................................. 280 Figure 32.6. PCA High-Speed Output Mode Diagram ........................................... 281 Figure 32.7. PCA Frequency Output Mode ........................................................... 282 Figure 32.8. PCA 8-Bit PWM Mode Diagram ........................................................ 283 Figure 32.9. PCA 9, 10 and 11-Bit PWM Mode Diagram ...................................... 284 Figure 32.10. PCA 16-Bit PWM Mode ................................................................... 285 Figure 32.11. PCA Module 2 with Watchdog Timer Enabled ................................ 286 Figure 32.12. Comparator Clear Function Diagram .............................................. 288 Figure 32.13. CEXn with CPCEn = 1, CPCPOL = 0 .............................................. 288 Figure 32.14. CEXn with CPCEn = 1, CPCPOL = 1 .............................................. 289 Figure 32.15. CEXn with CPCEn = 1, CPCPOL = 0 .............................................. 289 Figure 32.16. CEXn with CPCEn = 1, CPCPOL = 1 .............................................. 289 Figure 33.1. Typical C2 Pin Sharing ...................................................................... 300 10 Rev. 1.2

C8051F39x/37x Table 2.1. Product Selection Guide ......................................................................... 20 Table 3.1. C8051F33x Replacement Part Numbers ................................................ 21 Table 4.1. Pin Definitions for the C8051F39x/37x ................................................... 22 Table 5.1. QFN-20 Package Dimensions ................................................................ 28 Table 5.2. QFN-20 PCB Land Pattern Dimensions ................................................. 29 Table 6.1. QFN-24 Package Dimensions ................................................................ 30 Table 6.2. QFN-24 PCB Land Pattern Dimensions ................................................. 31 Table 7.1. Absolute Maximum Ratings .................................................................... 32 Table 7.2. Global Electrical Characteristics ............................................................. 33 Table 7.3. Port I/O DC Electrical Characteristics ..................................................... 35 Table 7.4. Reset Electrical Characteristics .............................................................. 36 Table 7.5. Flash Electrical Characteristics .............................................................. 37 Table 7.6. EEPROM Electrical Characteristics ........................................................ 37 Table 7.7. Internal High-Frequency Oscillator Electrical Characteristics ................. 38 Table 7.8. Internal Low-Frequency Oscillator Electrical Characteristics ................. 38 Table 7.9. Internal Low-Power Oscillator Electrical Characteristics ........................ 38 Table 7.10. ADC0 Electrical Characteristics ............................................................ 39 Table 7.11. ADC Temperature Sensor Electrical Characteristics ............................ 40 Table 7.12. Precision Temperature Sensor Electrical Characteristics .................... 40 Table 7.13. Voltage Reference Electrical Characteristics ....................................... 41 Table 7.14. Voltage Regulator Electrical Characteristics ........................................ 41 Table 7.15. IDAC Electrical Characteristics ............................................................. 42 Table 7.16. Comparator Electrical Characteristics .................................................. 43 Table 8.1. Example Temperature Values in TS0DATH:TS0DATL .......................... 47 Table 15.1. CIP-51 Instruction Set Summary .......................................................... 84 Table 19.1. SFR Page Stack ................................................................................. 101 Table 19.2. Special Function Register (SFR) Memory Map .................................. 111 Table 19.3. Special Function Registers ................................................................. 112 Table 20.1. Configurable Interrupt Priority Decoding ............................................ 118 Table 20.2. Interrupt Summary .............................................................................. 119 Table 21.1. Flash Security Summary .................................................................... 133 Table 23.1. Example 16-bit CRC Outputs ............................................................. 148 Table 27.1. Port I/O Assignment for Analog Functions ......................................... 175 Table 27.2. Port I/O Assignment for Digital Functions ........................................... 176 Table 27.3. Port I/O Assignment for External Event Trigger Functions ................. 177 Table 28.1. SMBus Clock Source Selection .......................................................... 196 Table 28.2. Minimum SDA Setup and Hold Times ................................................ 197 Table 28.3. Sources for Hardware Changes to SMBnCN ..................................... 204 Table 28.4. Hardware Address Recognition Examples (EHACK = 1) ................... 205 Table 28.5. SMBus Status Decoding: Hardware ACK Disabled (EHACK = 0) ...... 215 Table 28.6. SMBus Status Decoding: Hardware ACK Enabled (EHACK = 1) ...... 217 Table 29.1. Timer Settings for Standard Baud Rates Using The Internal 49 MHz Oscillator ................................................. 227 Table 29.2. Timer Settings for Standard Baud Rates Using an External 22.1184 MHz Oscillator ......................................... 227 Rev. 1.2 11

C8051F39x/37x Table 30.1. SPI Slave Timing Parameters ............................................................ 241 Table 32.1. PCA Timebase Input Options ............................................................. 276 Table 32.2. PCA0CPM and PCA0PWM Bit Settings for PCA Capture/Compare Mod- ules ..................................................................................................... 278 Table 32.3. Watchdog Timer Timeout Intervals1 ................................................... 287 12 Rev. 1.2

C8051F39x/37x SFR Definition 8.1. TS0CN: Temperature Sensor Control ........................................... 48 SFR Definition 8.2. TS0DATH: Temperature Sensor Output High Byte ....................... 49 SFR Definition 8.3. TS0DATL: Temperature Sensor Output Low Byte ........................ 49 SFR Definition 9.1. ADC0CF: ADC0 Configuration ...................................................... 55 SFR Definition 9.2. ADC0H: ADC0 Data Word MSB .................................................... 56 SFR Definition 9.3. ADC0L: ADC0 Data Word LSB ...................................................... 56 SFR Definition 9.4. ADC0CN: ADC0 Control ................................................................ 57 SFR Definition 9.5. ADC0GTH: ADC0 Greater Than Data High Byte .......................... 58 SFR Definition 9.6. ADC0GTL: ADC0 Greater-Than Data Low Byte ............................ 58 SFR Definition 9.7. ADC0LTH: ADC0 Less-Than Data High Byte ................................ 59 SFR Definition 9.8. ADC0LTL: ADC0 Less-Than Data Low Byte ................................. 59 SFR Definition 9.9. AMX0P: AMUX0 Positive Channel Select ..................................... 62 SFR Definition 9.10. AMX0N: AMUX0 Negative Channel Select ................................. 63 SFR Definition 11.1. IDA0CN: IDA0 Control ................................................................. 69 SFR Definition 11.2. IDA0H: IDA0 Data Word MSB ..................................................... 70 SFR Definition 11.3. IDA0L: IDA0 Data Word LSB ....................................................... 70 SFR Definition 11.4. IDA1CN: IDA1 Control ................................................................. 71 SFR Definition 11.5. IDA1H: IDA1 Data Word MSB ..................................................... 72 SFR Definition 11.6. IDA1L: IDA1 Data Word LSB ....................................................... 72 SFR Definition 12.1. REF0CN: Reference Control ....................................................... 74 SFR Definition 13.1. REG0CN: Voltage Regulator Control .......................................... 75 SFR Definition 14.1. CPT0CN: Comparator0 Control ................................................... 78 SFR Definition 14.2. CPT0MD: Comparator0 Mode Selection ..................................... 79 SFR Definition 14.3. CPT0MX: Comparator0 MUX Selection ...................................... 81 SFR Definition 15.1. DPL: Data Pointer Low Byte ........................................................ 88 SFR Definition 15.2. DPH: Data Pointer High Byte ....................................................... 88 SFR Definition 15.3. SP: Stack Pointer ......................................................................... 89 SFR Definition 15.4. ACC: Accumulator ....................................................................... 89 SFR Definition 15.5. B: B Register ................................................................................ 90 SFR Definition 15.6. PSW: Program Status Word ........................................................ 91 SFR Definition 16.1. PFE0CN: Prefetch Engine Control .............................................. 92 SFR Definition 17.1. EMI0CN: External Memory Interface Control .............................. 96 SFR Definition 18.1. DERIVID: Device Derivative ID .................................................... 97 SFR Definition 18.2. REVISION: Device Revision ID ................................................... 98 SFR Definition 18.3. SN3: Serial Number Byte 3 .......................................................... 98 SFR Definition 18.4. SN2: Serial Number Byte 2 .......................................................... 99 SFR Definition 18.5. SN1: Serial Number Byte 1 .......................................................... 99 SFR Definition 18.6. SN0: Serial Number Byte 0 ........................................................ 100 SFR Definition 19.1. SFRPAGE: SFR Page ............................................................... 108 SFR Definition 19.2. SFRPGCN: SFR Page Control .................................................. 109 SFR Definition 19.3. SFRSTACK: SFR Page Stack ................................................... 110 SFR Definition 20.1. IE: Interrupt Enable .................................................................... 120 SFR Definition 20.2. IP: Interrupt Priority .................................................................... 121 SFR Definition 20.3. IPH: Interrupt Priority High ......................................................... 122 SFR Definition 20.4. EIE1: Extended Interrupt Enable 1 ............................................ 123 Rev. 1.2 13

C8051F39x/37x SFR Definition 20.5. EIP1: Extended Interrupt Priority 1 ............................................ 124 SFR Definition 20.6. EIP1H: Extended Interrupt Priority 1 High ................................. 125 SFR Definition 20.7. EIE2: Extended Interrupt Enable 2 ............................................ 126 SFR Definition 20.8. EIP2: Extended Interrupt Priority 2 ............................................ 127 SFR Definition 20.9. EIP2H: Extended Interrupt Priority 2 High ................................. 127 SFR Definition 20.10. IT01CF: INT0/INT1 Configuration ............................................ 129 SFR Definition 21.1. PSCTL: Program Store R/W Control ......................................... 137 SFR Definition 21.2. FLKEY: Flash Lock and Key ...................................................... 138 SFR Definition 21.3. FLSCL: Flash Scale ................................................................... 139 SFR Definition 23.1. CRC0CN: CRC0 Control ........................................................... 150 SFR Definition 23.2. CRC0IN: CRC0 Data Input ........................................................ 151 SFR Definition 23.3. CRC0DAT: CRC0 Data Output .................................................. 151 SFR Definition 23.4. CRC0AUTO: CRC0 Automatic Control ...................................... 152 SFR Definition 23.5. CRC0CNT: CRC0 Automatic Flash Sector Count ..................... 153 SFR Definition 23.6. CRC0FLIP: CRC0 Bit Flip .......................................................... 154 SFR Definition 24.1. VDM0CN: VDD Monitor Control ................................................ 158 SFR Definition 24.2. RSTSRC: Reset Source ............................................................ 160 SFR Definition 25.1. PCON: Power Control ................................................................ 163 SFR Definition 26.1. CLKSEL: Clock Select ............................................................... 165 SFR Definition 26.2. OSCICL: Internal H-F Oscillator Calibration .............................. 166 SFR Definition 26.3. OSCICN: Internal H-F Oscillator Control ................................... 167 SFR Definition 26.4. OSCLCN: Internal L-F Oscillator Control ................................... 168 SFR Definition 26.5. OSCXCN: External Oscillator Control ........................................ 172 SFR Definition 27.1. XBR0: Port I/O Crossbar Register 0 .......................................... 181 SFR Definition 27.2. XBR1: Port I/O Crossbar Register 1 .......................................... 182 SFR Definition 27.3. P0MASK: Port 0 Mask Register ................................................. 183 SFR Definition 27.4. P0MAT: Port 0 Match Register .................................................. 184 SFR Definition 27.5. P1MASK: Port 1 Mask Register ................................................. 184 SFR Definition 27.6. P1MAT: Port 1 Match Register .................................................. 185 SFR Definition 27.7. P0: Port 0 ................................................................................... 186 SFR Definition 27.8. P0MDIN: Port 0 Input Mode ....................................................... 186 SFR Definition 27.9. P0MDOUT: Port 0 Output Mode ................................................ 187 SFR Definition 27.10. P0SKIP: Port 0 Skip ................................................................. 187 SFR Definition 27.11. P1: Port 1 ................................................................................. 188 SFR Definition 27.12. P1MDIN: Port 1 Input Mode ..................................................... 188 SFR Definition 27.13. P1MDOUT: Port 1 Output Mode .............................................. 189 SFR Definition 27.14. P1SKIP: Port 1 Skip ................................................................. 189 SFR Definition 27.15. P2: Port 2 ................................................................................. 190 SFR Definition 27.16. P2MDIN: Port 2 Input Mode ..................................................... 190 SFR Definition 27.17. P2MDOUT: Port 2 Output Mode .............................................. 191 SFR Definition 27.18. P2SKIP: Port 2 Skip ................................................................. 191 SFR Definition 28.1. SMB0CF: SMBus Clock/Configuration ...................................... 198 SFR Definition 28.2. SMB1CF: SMBus Clock/Configuration ...................................... 199 SFR Definition 28.3. SMBTC: SMBus Timing and Pin Control ................................... 200 SFR Definition 28.4. SMB0CN: SMBus Control .......................................................... 202 14 Rev. 1.2

C8051F39x/37x SFR Definition 28.5. SMB1CN: SMBus Control .......................................................... 203 SFR Definition 28.6. SMB0ADR: SMBus0 Slave Address .......................................... 205 SFR Definition 28.7. SMB0ADM: SMBus0 Slave Address Mask ................................ 206 SFR Definition 28.8. SMB1ADR: SMBus1 Slave Address .......................................... 207 SFR Definition 28.9. SMB1ADM: SMBus1 Slave Address Mask ................................ 208 SFR Definition 28.10. SMB0DAT: SMBus Data .......................................................... 209 SFR Definition 28.11. SMB1DAT: SMBus Data .......................................................... 210 SFR Definition 29.1. SCON0: Serial Port 0 Control .................................................... 225 SFR Definition 29.2. SBUF0: Serial (UART0) Port Data Buffer .................................. 226 SFR Definition 30.1. SPI0CFG: SPI0 Configuration ................................................... 235 SFR Definition 30.2. SPI0CN: SPI0 Control ............................................................... 236 SFR Definition 30.3. SPI0CKR: SPI0 Clock Rate ....................................................... 237 SFR Definition 30.4. SPI0DAT: SPI0 Data ................................................................. 238 SFR Definition 31.1. CKCON: Clock Control .............................................................. 243 SFR Definition 31.2. CKCON1: Clock Control 1 ......................................................... 244 SFR Definition 31.3. TCON: Timer Control ................................................................. 249 SFR Definition 31.4. TMOD: Timer Mode ................................................................... 250 SFR Definition 31.5. TL0: Timer 0 Low Byte ............................................................... 251 SFR Definition 31.6. TL1: Timer 1 Low Byte ............................................................... 251 SFR Definition 31.7. TH0: Timer 0 High Byte ............................................................. 252 SFR Definition 31.8. TH1: Timer 1 High Byte ............................................................. 252 SFR Definition 31.9. TMR2CN: Timer 2 Control ......................................................... 256 SFR Definition 31.10. TMR2RLL: Timer 2 Reload Register Low Byte ........................ 257 SFR Definition 31.11. TMR2RLH: Timer 2 Reload Register High Byte ...................... 257 SFR Definition 31.12. TMR2L: Timer 2 Low Byte ....................................................... 257 SFR Definition 31.13. TMR2H Timer 2 High Byte ....................................................... 258 SFR Definition 31.14. TMR3CN: Timer 3 Control ....................................................... 262 SFR Definition 31.15. TMR3RLL: Timer 3 Reload Register Low Byte ........................ 263 SFR Definition 31.16. TMR3RLH: Timer 3 Reload Register High Byte ...................... 263 SFR Definition 31.17. TMR3L: Timer 3 Low Byte ....................................................... 263 SFR Definition 31.18. TMR3H Timer 3 High Byte ....................................................... 264 SFR Definition 31.19. TMR4CN: Timer 4 Control ....................................................... 267 SFR Definition 31.20. TMR4RLL: Timer 4 Reload Register Low Byte ........................ 268 SFR Definition 31.21. TMR4RLH: Timer 4 Reload Register High Byte ...................... 268 SFR Definition 31.22. TMR4L: Timer 4 Low Byte ....................................................... 268 SFR Definition 31.23. TMR4H Timer 4 High Byte ....................................................... 269 SFR Definition 31.24. TMR5CN: Timer 5 Control ....................................................... 272 SFR Definition 31.25. TMR5RLL: Timer 5 Reload Register Low Byte ........................ 273 SFR Definition 31.26. TMR5RLH: Timer 5 Reload Register High Byte ...................... 273 SFR Definition 31.27. TMR5L: Timer 5 Low Byte ....................................................... 273 SFR Definition 31.28. TMR5H Timer 5 High Byte ....................................................... 274 SFR Definition 32.1. PCA0CN: PCA Control .............................................................. 290 SFR Definition 32.2. PCA0MD: PCA Mode ................................................................ 291 SFR Definition 32.3. PCA0PWM: PCA PWM Configuration ....................................... 292 SFR Definition 32.4. PCA0CLR: PCA Comparator Clear Control ............................... 293 Rev. 1.2 15

C8051F39x/37x SFR Definition 32.5. PCA0CPMn: PCA Capture/Compare Mode .............................. 294 SFR Definition 32.6. PCA0L: PCA Counter/Timer Low Byte ...................................... 295 SFR Definition 32.7. PCA0H: PCA Counter/Timer High Byte ..................................... 295 SFR Definition 32.8. PCA0CPLn: PCA Capture Module Low Byte ............................. 296 SFR Definition 32.9. PCA0CPHn: PCA Capture Module High Byte ........................... 296 C2 Register Definition 33.1. C2ADD: C2 Address ...................................................... 297 C2 Register Definition 33.2. DEVICEID: C2 Device ID ............................................... 298 C2 Register Definition 33.3. REVID: C2 Revision ID .................................................. 298 C2 Register Definition 33.4. FPCTL: C2 Flash Programming Control ........................ 299 C2 Register Definition 33.5. FPDAT: C2 Flash Programming Data ............................ 299 16 Rev. 1.2

C8051F39x/37x 1. System Overview C8051F39x/37x devices are fully integrated mixed-signal System-on-a-Chip MCUs. Highlighted features are listed below. Refer to Section “2.Ordering Information” on page20 for specific product feature selec- tion and part ordering numbers.  High-speed pipelined 8051-compatible microcontroller core (up to 50MIPS)  In-system, full-speed, non-intrusive debug interface (on-chip)  True 10-bit 500ksps 20 or 16-channel single-ended/differential ADC with analog multiplexer  Two 10-bit Current Output DACs  Precision temperature sensor with ±2°C absolute accuracy  Precision programmable 49MHz internal oscillator  Low-power, low-frequency oscillator  16kB of on-chip Flash memory  1024 bytes of on-chip RAM  Co-packaged with 512 bytes of EEPROM memory, accessible via I2C (C8051F37x)  Two SMBus/I2C, UART, and SPI serial interfaces implemented in hardware  Six general-purpose 16-bit timers  Programmable Counter/Timer Array (PCA) with three capture/compare modules and Watchdog Timer function  On-chip Power-On Reset, VDD Monitor, and Temperature Sensor  On-chip Voltage Comparator  21 or 17 Port I/O  Low-power suspend mode with fast wake-up time With on-chip Power-On Reset, V monitor, Watchdog Timer, and clock oscillator, the C8051F39x/37x DD devices are truly stand-alone System-on-a-Chip solutions. The Flash memory can be reprogrammed even in-circuit, providing non-volatile data storage, and also allowing field upgrades of the 8051 firmware. User software has complete control of all peripherals, and may individually shut down any or all peripherals for power savings. The on-chip Silicon Labs 2-Wire (C2) Development Interface allows non-intrusive (uses no on-chip resources), full speed, in-circuit debugging using the production MCU installed in the final application. This debug logic supports inspection and modification of memory and registers, setting breakpoints, single stepping, run and halt commands. All analog and digital peripherals are fully functional while debugging using C2. The two C2 interface pins can be shared with user functions, allowing in-system debugging with- out occupying package pins. The C8051F37x devices are specified for 1.8 to 3.6V operation over the industrial temperature range (–40 to +85°C), while the C8051F39x devices operate over an extended temperature range (-40 to +105°C). The C8051F392/3/6/7/8/9 are available in a 20-pin QFN package and the C8051F390/1/4/5 and C8051F37x are available in a 24-pin QFN package. Both package options are lead-free and RoHS compli- ant. See Section “2.Ordering Information” on page20 for ordering information. Block diagrams are included in Figure1.1, Figure1.2 and Figure1.3. Rev. 1.2 17

C8051F39x/37x Power On CIP-51 8051 Port I/O Configuration Reset Controller Core P0.0/VREF Digital Peripherals P0.1/IDA0 Reset 16/8/4 kB ISP Flash UART P0.2/XTAL1 C2CK/RST Debug / Program Memory Port 0 P0.3/XTAL2 Programming Timers 0 Drivers P0.4/TX Hardware 256 Byte SRAM through 5 P0.5/RX Priority P0.6/CNVSTR C2D PWCDAT/ CDreocsosdbearr P0.7 768 Byte XRAM P1.0/IDA1 2xI2C / P1.1 SMBus P1.2 SPI Port 1 P1.3 Drivers P1.4 Crossbar Control Internal Power Net P1.5 VDD LDO SFR P1.6 GND Bus Analog Peripherals P1.7 P2.0/C2D Port 2 2 x 10-bit IDA0 Drivers IDA1 Precision IDACs 49 MHz Oscillator Precision Temperature Sensor Low-Freq. SYSCLK Oscillator 10-bit A 500 ksps M U XTAL1 External ADC X Oscillator XTAL2 Circuit C8051F392/6/8 Only System Clock CP0, CP0A + Configuration - Comparator Figure 1.1. C8051F392/3/6/7/8/9 Block Diagram Power On CIP-51 8051 Port I/O Configuration Reset Controller Core P0.0/VREF Digital Peripherals P0.1/IDA0 Reset 16/8 kB ISP Flash P0.2/XTAL1 UART C2CK/RST Debug / Program Memory Port 0 P0.3/XTAL2 Programming Timers 0 Drivers P0.4/TX Hardware 256 Byte SRAM through 5 P0.5/RX Priority P0.6/CNVSTR C2D PWCDAT/ CDreocsosdbearr P0.7 768 Byte XRAM P1.0 2xI2C / P1.1 SMBus P1.2/IDA1 SPI Port 1 P1.3 Drivers P1.4 Crossbar Control Internal Power Net P1.5 VDD LDO SFR P1.6 GND Bus Analog Peripherals P1.7 P2.0 P2.1 Precision 2ID xA 1C0s-bit IIDDAA01 DProivret r2s PP22..23 49 MHz P2.4/C2D Oscillator Precision Temperature Sensor Low-Freq. SYSCLK Oscillator 10-bit A 500 ksps M U XTAL1 External ADC X Oscillator XTAL2 Circuit C8051F390/4 Only System Clock CP0, CP0A + Configuration - Comparator Figure 1.2. C8051F390/1/4/5 Block Diagram 18 Rev. 1.2

C8051F39x/37x Power On CIP-51 8051 Port I/O Configuration Reset Controller Core P0.0/VREF Digital Peripherals P0.1/IDA0 Reset 16 kB ISP Flash UART P0.2/XTAL1 C2CK/RST Debug / Program Memory Port 0 P0.3/XTAL2 Programming Timers 0 Drivers P0.4/TX Hardware 256 Byte SRAM through 5 P0.5/RX Priority P0.6/CNVSTR C2D PWCDAT/ CDreocsosdbearr P0.7 768 Byte XRAM P1.0 2xI2C / P1.1 SMBus P1.2/IDA1 EESDA SPI Port 1 P1.3 512 Byte I2C EEPROM Drivers P1.4 EESCL Crossbar Control P1.5 SFR P1.6 VDD InLteDrOnal Power Net Bus Analog Peripherals P1.7 P2.0 GND P2.1 Precision 2ID xA 1C0s-bit IIDDAA01 DProivret r2s PP22..23//EEEESSCDLA 49 MHz P2.4/C2D Oscillator Precision Temperature Sensor Low-Freq. SYSCLK Oscillator 10-bit A M 500 ksps U XTAL1 External ADC X Oscillator XTAL2 Circuit C8051F370/4 Only System Clock CP0, CP0A + Configuration - Comparator Figure 1.3. C8051F370/1/4/5 Block Diagram Rev. 1.2 19

C8051F39x/37x 2. Ordering Information The following features are common to all device in this family:  50 MIPS throughput (peak)  1kB of RAM (256 internal bytes and 768 XRAM bytes)  Calibrated internal 49MHz oscillator  Internal 80kHz oscillator  Two SMBus/I2C  Enhanced SPI, Enhanced UART  Six Timers  Three Programmable Counter Array channels  Analog Comparator  Lead-free / RoHS Compliant Table2.1 shows the features that differentiate the devices in this family. Table 2.1. Product Selection Guide Ordering Part Flash EEPROM Digital 10-bit 10-bit On-Chip Precision Package Number Memory (Bytes) Port I/Os ADC DAC Voltage Temperature 4x4 mm (Bytes) Channels Channels Reference Sensor C8051F390-A-GM 16k — 21 20 2 Y Y QFN-24 C8051F391-A-GM 16k — 21 — — — — QFN-24 C8051F392-A-GM 16k — 17 16 2 Y Y QFN-20 C8051F393-A-GM 16k — 17 — — — — QFN-20 C8051F394-A-GM 8k — 21 20 2 Y Y QFN-24 C8051F395-A-GM 8k — 21 — — — — QFN-24 C8051F396-A-GM 8k — 17 16 2 Y Y QFN-20 C8051F397-A-GM 8k — 17 — — — — QFN-20 C8051F398-A-GM 4k — 17 16 2 Y Y QFN-20 C8051F399-A-GM 4k — 17 — — — — QFN-20 C8051F370-A-GM1 16k 512 21 20 2 Y Y QFN-24 C8051F371-A-GM1 16k 512 21 — — — — QFN-24 C8051F374-A-GM1 8k 512 21 20 2 Y Y QFN-24 C8051F375-A-GM1 8k 512 21 — — — — QFN-24 Notes: 1. These devices are not recommended for new designs. 20 Rev. 1.2

C8051F39x/37x 3. C8051F33x Compatibility The C8051F39x/37x family is designed to be a pin and code compatible replacement for the C8051F33x device family, with an enhanced feature set. The C8051F39x/37x device should function as a drop-in replacement for the C8051F33x devices in most applications. Table3.1 lists recommended replacement part numbers for C8051F33x devices. See “3.1. Hardware Incompatibilities” to determine if any changes are necessary when upgrading an existing C8051F33x design to the C8051F39x/37x. Table 3.1. C8051F33x Replacement Part Numbers C8051F33x Part Number C8051F39x/37x Part Number C8051F330-GM C8051F396-A-GM C8051F331-GM C8051F397-A-GM C8051F332-GM C8051F398-A-GM C8051F333-GM C8051F399-A-GM C8051F334-GM C8051F398-A-GM C8051F335-GM C8051F399-A-GM C8051F336-GM C8051F392-A-GM C8051F337-GM C8051F393-A-GM C8051F338-GM C8051F390-A-GM C8051F339-GM C8051F391-A-GM 3.1. Hardware Incompatibilities While the C8051F39x/37x family includes a number of new features not found on the C8051F33x family, there are some differences that should be considered for any design port.  Internal High-Frequency Oscillator: The undivided high-frequency oscillator on the C8051F39x/37x is 49MHz, whereas the undivided high-frequency oscillator on the C8051F33x is 24.5MHz. Correspondingly, the internal high frequency divide ratios (IFCN) have doubled. Thus, firmware written for the C8051F33x where the CLKSL[1:0] = 00b will result in the same SYSCLK frequency on the C8051F39x/37x.  Fabrication Technology: The C8051F39x/37x is manufactured using a different technology process than the C8051F33x. As a result, many of the electrical performance parameters will have subtle differences. These differences should not affect most systems but it is nonetheless important to review the electrical parameters for any blocks that are used in the design, and ensure they are compatible with the existing hardware.  5V Tolerance: The port I/O pins on the C8501F39x/37x are not 5V tolerant, whereas the port I/O pins on the C8051F33x are 5V tolerant.  Lock Byte Address: The lock byte for C8051F39x/7x devices with 16 kB of Flash resides at address 0x3FFF, whereas the lock byte for C8051F33x devices with 16 kB of Flash resides at address 0x3DFF. The lock byte for C8051F39x/7x devices with 8 kB of Flash resides at address 0x1FFF, whereas the lock byte for C8051F33x devices with 8 kB of Flash resides at address 0x1DFF. Rev. 1.2 21

C8051F39x/37x 4. Pin Definitions Table 4.1. Pin Definitions for the C8051F39x/37x Name Pin Pin Pin Type Description ‘F392/3/6/ ’F390/1/ ’F370/1/ 7/8/9 4/5 4/5 V 3 4 4 Power Supply Voltage. DD GND 2 3 3 Ground. This ground connection is required. The center pad may optionally be connected to ground also. RST/ 4 5 5 D I/O Device Reset. Open-drain output of internal POR or V monitor. An external source can ini- DD tiate a system reset by driving this pin low for at least 10µs. C2CK D I/O Clock signal for the C2 Debug Interface. C2D 5 6 6 D I/O Bi-directional data signal for the C2 Debug Inter- face. Shared with P2.0 on 20-pin packaging and P2.4 on 24-pin packaging. P0.0/ 1 2 2 D I/O or Port 0.0. A In VREF A In External VREF input. P0.1 20 1 1 D I/O or Port 0.1. A In IDA0 A Out IDA0 Output. P0.2/ 19 24 24 D I/O or Port 0.2. A In XTAL1 A In External Clock Input. This pin is the external oscillator return for a crystal or resonator. P0.3/ 18 23 23 D I/O or Port 0.3. A In XTAL2 A I/O or External Clock Output. For an external crystal or D In resonator, this pin is the excitation driver. This pin is the external clock input for CMOS, capaci- tor, or RC oscillator configurations. P0.4 17 22 22 D I/O or Port 0.4. A In P0.5 16 21 21 D I/O or Port 0.5. A In 22 Rev. 1.2

C8051F39x/37x Table 4.1. Pin Definitions for the C8051F39x/37x (Continued) Name Pin Pin Pin Type Description ‘F392/3/6/ ’F390/1/ ’F370/1/ 7/8/9 4/5 4/5 P0.6/ 15 20 20 D I/O or Port 0.6. A In CNVSTR D In ADC0 External Convert Start or IDA0 Update Source Input. P0.7 14 19 19 D I/O or Port 0.7. A In P1.0 13 — — D I/O or Port 1.0. A In IDA1 A Out IDA1 Output. P1.0 18 18 D I/O or Port 1.0. A In P1.1 12 17 17 D I/O or Port 1.1. A In P1.2 - 16 16 D I/O or Port 1.2. A In IDA1 A Out IDA1 Output. P1.2 11 — — D I/O or Port 1.2. A In P1.3 10 15 15 D I/O or Port 1.3. A In P1.4 9 14 14 D I/O or Port 1.4. A In P1.5 8 13 13 D I/O or Port 1.5. A In P1.6 7 12 12 D I/O or Port 1.6. A In P1.7 6 11 11 D I/O or Port 1.7. A In P2.0 5 10 10 D I/O or Port 2.0. (Also C2D on 20-pin Packaging) A In P2.1 — 9 9 D I/O or Port 2.1. A In Rev. 1.2 23

C8051F39x/37x Table 4.1. Pin Definitions for the C8051F39x/37x (Continued) Name Pin Pin Pin Type Description ‘F392/3/6/ ’F390/1/ ’F370/1/ 7/8/9 4/5 4/5 P2.2 — 8 — D I/O or Port 2.2. A In P2.2 - — 8 D I/O or Port 2.2. A In EESCL D I/O EEPROM SCL Connection. P2.3 — 7 — D I/O or Port 2.3. A In P2.3 - — 7 D I/O or Port 2.3. A In EESDA D I/O EEPROM SDA Connection. P2.4 — 6 6 D I/O Port 2.4. (Also C2D on 24-pin Packaging) 24 Rev. 1.2

C8051F39x/37x 1 2 3 4 5 . . . . . 0 0 0 0 0 P P P P P 0 9 8 7 6 2 1 1 1 1 P0.0 1 15 P0.6 GND 2 14 P0.7 QFN-20 VDD 3 13 P1.0 Top View /RST/C2CK 4 12 P1.1 P2.0/C2D 5 GND (optional) 11 P1.2 0 6 7 8 9 1 7 6 5 4 3 . . . . . 1 1 1 1 1 P P P P P Figure 4.1. C8051F392/3/6/7/8/9 QFN-20 Pinout Diagram (Top View) Rev. 1.2 25

C8051F39x/37x 2 3 4 5 6 7 . . . . . . 0 0 0 0 0 0 P P P P P P 4 3 2 1 0 9 2 2 2 2 2 1 P0.1 1 18 P1.0 P0.0 2 17 P1.1 GND 3 16 P1.2 QFN-24 Top View VDD 4 15 P1.3 /RST/C2CK 5 14 P1.4 GND (optional) P2.4/C2D 6 13 P1.5 0 1 2 7 8 9 1 1 1 3 2 1 0 7 6 . . . . . . 2 2 2 2 1 1 P P P P P P Figure 4.2. C8051F390/1/4/5 Pinout Diagram (Top View) 26 Rev. 1.2

C8051F39x/37x 2 3 4 5 6 7 . . . . . . 0 0 0 0 0 0 P P P P P P 4 3 2 1 0 9 2 2 2 2 2 1 P0.1 1 18 P1.0 P0.0 2 17 P1.1 GND 3 16 P1.2 QFN-24 Top View VDD 4 15 P1.3 /RST/C2CK 5 14 P1.4 GND (optional) P2.4/C2D 6 13 P1.5 0 1 2 7 8 9 1 1 1 A L 1 0 7 6 D C 2. 2. 1. 1. S S P P P P E E E E 3/ 2/ 2. 2. P P Figure 4.3. C8051F370/1/4/5 Pinout Diagram (Top View) Rev. 1.2 27

C8051F39x/37x 5. QFN-20 Package Specifications Figure 5.1. QFN-20 Package Drawing Table 5.1. QFN-20 Package Dimensions Dimension Min Typ Max Dimension Min Typ Max A 0.80 0.85 0.90 L 0.50 0.55 0.60 A1 0.00 0.035 0.05 aaa — — 0.10 b 0.20 0.25 0.30 bbb — — 0.10 D 4.00 BSC. ccc — — 0.08 D2 2.00 2.10 2.20 ddd — — 0.10 e 0.50 BSC. eee — — 0.10 E 4.00 BSC. ggg 0.05 E2 2.00 2.10 2.20 Notes: 1. All dimensions shown are in millimeters (mm) unless otherwise noted. 2. Dimensioning and Tolerancing per ANSI Y14.5M-1994. 3. This drawing conforms to the JEDEC Solid State Outline MO-220, variation VGGD except for custom features D2, E2, Z, Y, and L which are toleranced per supplier designation. 4. Recommended card reflow profile is per the JEDEC/IPC J-STD-020C specification for Small Body Components. 28 Rev. 1.2

C8051F39x/37x Figure 5.2. QFN-20 Recommended PCB Land Pattern Table 5.2. QFN-20 PCB Land Pattern Dimensions Dimension Max Dimension Max C1 3.80 X2 2.20 C2 3.80 Y1 1.00 E 0.50 Y2 2.20 X1 0.30 Notes: General 1. All dimensions shown are in millimeters (mm) unless otherwise noted. 2. Dimensioning and Tolerancing is per the ANSI Y14.5M-1994 specification. 3. This Land Pattern Design is based on the IPC-7351 guidelines. Solder Mask Design 4. All metal pads are to be non-solder mask defined (NSMD). Clearance between the solder mask and the metal pad is to be 60µm minimum, all the way around the pad. Stencil Design 5. A stainless steel, laser-cut and electro-polished stencil with trapezoidal walls should be used to assure good solder paste release. 6. The stencil thickness should be 0.125mm (5mils). 7. The ratio of stencil aperture to land pad size should be 1:1 for all perimeter pins. 8. A 2x2 array of 0.95mm openings on a 1.1mm pitch should be used for the center pad to assure the proper paste volume (71% Paste Coverage). Card Assembly 9. A No-Clean, Type-3 solder paste is recommended. 10. The recommended card reflow profile is per the JEDEC/IPC J-STD-020C specification for Small Body Components. Rev. 1.2 29

C8051F39x/37x 6. QFN-24 Package Specifications Figure 6.1. QFN-24 Package Drawing Table 6.1. QFN-24 Package Dimensions Dimension Min Typ Max Dimension Min Typ Max A 0.70 0.75 0.80 L 0.30 0.40 0.50 A1 0.00 0.02 0.05 L1 0.00 — 0.15 b 0.18 0.25 0.30 aaa — — 0.15 D 4.00 BSC. bbb — — 0.10 D2 2.55 2.70 2.80 ddd — — 0.05 e 0.50 BSC. eee — — 0.08 E 4.00 BSC. Z — 0.24 — E2 2.55 2.70 2.80 Y — 0.18 — Notes: 1. All dimensions shown are in millimeters (mm) unless otherwise noted. 2. Dimensioning and Tolerancing per ANSI Y14.5M-1994. 3. This drawing conforms to JEDEC Solid State Outline MO-220, variation WGGD except for custom features D2, E2, Z, Y, and L which are toleranced per supplier designation. 4. Recommended card reflow profile is per the JEDEC/IPC J-STD-020C specification for Small Body Components. 30 Rev. 1.2

C8051F39x/37x Figure 6.2. QFN-24 Recommended PCB Land Pattern Table 6.2. QFN-24 PCB Land Pattern Dimensions Dimension Min Max Dimension Min Max C1 3.90 4.00 X2 2.70 2.80 C2 3.90 4.00 Y1 0.65 0.75 E 0.50 BSC Y2 2.70 2.80 X1 0.20 0.30 Notes: General 1. All dimensions shown are in millimeters (mm) unless otherwise noted. 2. This Land Pattern Design is based on the IPC-7351 guidelines. Solder Mask Design 3. All metal pads are to be non-solder mask defined (NSMD). Clearance between the solder mask and the metal pad is to be 60µm minimum, all the way around the pad. Stencil Design 4. A stainless steel, laser-cut and electro-polished stencil with trapezoidal walls should be used to assure good solder paste release. 5. The stencil thickness should be 0.125mm (5mils). 6. The ratio of stencil aperture to land pad size should be 1:1 for all perimeter pads. 7. A 2 x 2 array of 1.10mm x 1.10mm openings on a 1.30mm pitch should be used for the center pad. Card Assembly 8. A No-Clean, Type-3 solder paste is recommended. 9. The recommended card reflow profile is per the JEDEC/IPC J-STD-020C specification for Small Body Components. Rev. 1.2 31

C8051F39x/37x 7. Electrical Characteristics 7.1. Absolute Maximum Specifications Table 7.1. Absolute Maximum Ratings Parameter Test Condition Min Typ Max Unit Ambient Temperature under Bias –55 — 125 °C Storage Temperature –65 — 150 °C Voltage on any Port I/O Pin or RST with –0.3 — V + 0.3 V DD respect to GND Voltage on V with Respect to GND –0.3 — 4.2 V DD Maximum Total Current through V or GND — — 100 mA DD Maximum Output Current Sunk by RST or — — 100 mA any Port Pin Note: Stresses above those listed under “Absolute Maximum Ratings” may cause permanent damage to the device. This is a stress rating only and functional operation of the devices at those or any other conditions above those indicated in the operation listings of this specification is not implied. Exposure to maximum rating conditions for extended periods may affect device reliability. 32 Rev. 1.2

C8051F39x/37x 7.2. Electrical Characteristics Table 7.2. Global Electrical Characteristics –40 to +105°C (C8051F39x), –40 to +85°C (C8051F37x), 50MHz system clock, unless otherwise specified. Parameter Test Condition Min Typ Max Unit Supply Voltage (V ) Normal Operation V 1 3.0 3.6 V DD RST Writing or Erasing Flash Memory 1.8 3.0 3.6 V Digital Supply RAM Data — 1.5 — V Retention Voltage SYSCLK (System Clock) 2 0 — 50 MHz T (SYSCLK High Time) 9.5 — — ns SYSH T (SYSCLK Low Time) 9.5 — — ns SYSL Specified Operating C8051F39x –40 — +105 °C Temperature Range C8051F37x –40 — +85 °C Digital Supply Current—CPU Active (Normal Mode, Fetching Instructions from Flash) I 3, 4 V =3.6V, F=50 MHz — 7.1 7.8 mA DD DD V =3.0V, F=50MHz — 7.0 7.7 mA DD V =3.6V, F=25MHz — 4.6 5.2 mA DD V =3.0V, F=25MHz — 4.5 5.1 mA DD V =3.6V, F=1MHz — 0.35 — mA DD V =3.0V, F=1MHz — 0.35 — mA DD V =3.0V, F=80kHz — 0.25 — mA DD Notes: 1. Given in Table7.4 on page36. 2. SYSCLK must be at least 32kHz to enable debugging. 3. Based on device characterization data; Not production tested. 4. Digital Supply Current depends on the particular code being executed. The values in this table are obtained with the CPU executing an “sjmp $” loop, which is the compiled form of a while(1) loop in C. One iteration requires 3 CPU clock cycles, and the Flash memory is read on each cycle. The supply current will vary slightly based on the physical location of the sjmp instruction and the number of Flash address lines that toggle as a result. In the worst case, current can increase by up to 30% if the sjmp loop straddles a 64-byte Flash address boundary (e.g., 0x007F to 0x0080). Real-world code with larger loops and longer linear sequences will have few transitions across the 64-byte boundary. Rev. 1.2 33

C8051F39x/37x Table 7.2. Global Electrical Characteristics (Continued) –40 to +105°C (C8051F39x), –40 to +85°C (C8051F37x), 50MHz system clock, unless otherwise specified. Parameter Test Condition Min Typ Max Unit Digital Supply Current—CPU Inactive (Idle Mode, Not Fetching Instructions from Flash) I 3 V =3.6V, F=50MHz — 3.9 4.5 mA DD DD V =3.0V, F=50MHz — 3.8 4.4 mA DD V =3.6V, F=25MHz — 2.1 2.5 mA DD V =3.0V, F=25MHz — 2.0 2.4 mA DD V =3.6V, F=1MHz — 0.15 — mA DD V =3.0V, F=1MHz — 0.15 — mA DD V =3.0V, F=80kHz — 0.1 — mA DD Digital Supply Current Oscillator not running, — 73 — µA (Suspend Mode) V Monitor Disabled, DD Regulator running (STOPCF=0) Digital Supply Current Oscillator not running, — 75 — µA (Stop Mode) V Monitor Disabled, DD Regulator running (STOPCF=0) Digital Supply Current Oscillator not running, — 0.2 — µA (Stop Mode, Regulator V Monitor Disabled, DD Shutdown) Regulator Shutdown (STOPCF = 1) Notes: 1. Given in Table7.4 on page36. 2. SYSCLK must be at least 32kHz to enable debugging. 3. Based on device characterization data; Not production tested. 4. Digital Supply Current depends on the particular code being executed. The values in this table are obtained with the CPU executing an “sjmp $” loop, which is the compiled form of a while(1) loop in C. One iteration requires 3 CPU clock cycles, and the Flash memory is read on each cycle. The supply current will vary slightly based on the physical location of the sjmp instruction and the number of Flash address lines that toggle as a result. In the worst case, current can increase by up to 30% if the sjmp loop straddles a 64-byte Flash address boundary (e.g., 0x007F to 0x0080). Real-world code with larger loops and longer linear sequences will have few transitions across the 64-byte boundary. 34 Rev. 1.2

C8051F39x/37x Table 7.3. Port I/O DC Electrical Characteristics V =1.8 to 3.6V, –40 to +105°C (C8051F39x), –40 to +85°C (C8051F37x), unless otherwise specified. DD Parameters Test Condition Min Typ Max Unit Standard Port I/O Output High Voltage I =–3mA, Port I/O push-pull V –0.7 — — V OH DD I =–10µA, Port I/O push-pull V –0.1 — — V OH DD I =–10mA, Port I/O push-pull — V –0.8 — V OH DD Output Low Voltage I =8.5mA — — 0.6 V OL I =10µA — — 0.1 V OL I =10mA, 1.8V ≤ V < 2.7V — 0.8 — V OL DD I =25mA, 2.7V ≤ V ≤ 3.6V — 1.0 — V OL DD Input High Voltage 1.8V ≤ V < 2.7V V –0.4 — — V DD DD 2.7V ≤ V ≤ 3.6V V –0.5 — — V DD DD Input Low Voltage 1.8V ≤ V < 2.7V — — 0.5 V DD 2.7V ≤ V ≤ 3.6V — — 0.6 V DD Input Leakage Weak Pullup Off — — ±1 µA Current Weak Pullup On, V =0V — 20 100 µA IN EESDA and EESCL (C8051F37x Only)* Output Low Voltage I =0.15mA, V =1.8V — — 0.2 V OL DD (EESDA) Output Low Voltage I =2.1mA, V =3V — — 0.4 V OL DD (EESDA) Output Leakage EEPUE = 0, V =3.6V, — — 2 µA DD Current 0V ≤ V ≤ V OUT DD (EESDA) Input High Voltage V x 0.7 — — V DD Input Low Voltage — — V x 0.3 V DD Input Leakage EEPUE = 0, Standby, V =3.6V, — — ±3 µA DD Current 0V ≤ V ≤ V IN DD Note: Applicable when interfacing to the C8051F37x EEPROM. Otherwise, standard port I/O characteristics apply. Rev. 1.2 35

C8051F39x/37x Table 7.4. Reset Electrical Characteristics –40 to +105°C (C8051F39x), –40 to +85°C (C8051F37x), unless otherwise specified. Parameter Test Condition Min Typ Max Unit RST Output Low Voltage I =4mA, — — 0.6 V OL V =1.8 to 3.6V DD RST Input Low Voltage — — 0.6 V RST Input Pullup Current RST=0.0V — 20 100 µA V POR Threshold (V ) V 1.7 1.75 1.8 V DD RST RST_LOW V 2.4 2.55 2.7 V RST_HIGH Missing Clock Detector Time- Time from last system clock 80 580 800 µs out rising edge to reset initiation Reset Time Delay Delay between release of any — — 40 µs reset source and code execution at location 0x0000 Minimum RST Low Time to 15 — — µs Generate a System Reset V Monitor Turn-on Time 100 — — µs DD V Monitor Supply Current — 20 50 µA DD 36 Rev. 1.2

C8051F39x/37x Table 7.5. Flash Electrical Characteristics V =1.8 to 3.6V, –40 to +105°C (C8051F39x), –40 to +85°C (C8051F37x), unless otherwise specified. DD Parameter Test Condition Min Typ Max Unit Flash Size C8051F390/1/2/3, C8051F370/1 16384 Bytes C8051F394/5/6/7, C8051F374/5 8192 Bytes C8051F398/9 4096 Bytes Endurance 20000 100000 — Erase/Write Erase Cycle Time 23 25 27 ms Write Cycle Time 58 61 64 µs Table 7.6. EEPROM Electrical Characteristics V =1.8 to 3.6V, –40 to +85°C (C8051F37x), unless otherwise specified. DD Parameter Test Condition Min Typ Max Unit EEPROM Size 512 Bytes Endurance 1000000 — — Write Cycles Write Cycle Time 16-byte page — — 3.5 ms EESCL Clock Frequency — — 400 kHz Supply Current — — 3 µA — — 2 mA V =3.6V, Write — — 3 mA DD Rev. 1.2 37

C8051F39x/37x Table 7.7. Internal High-Frequency Oscillator Electrical Characteristics V =1.8 to 3.6V, –40 to +105°C (C8051F39x), –40 to +85°C (C8051F37x), using factory-calibrated settings, DD unless otherwise specified. Parameter Test Condition Min Typ Max Unit Oscillator Frequency C8051F390/1/2/3, 48 49 50 MHz C8051F370/1 Oscillator Supply Current C8051F394/5/6/7, — 840 880 µA (from VDD) C8051F374/5 Power Supply Sensitivity C8051F398/9 — 0.12 — %/V Temperature Sensitivity — 90 — ppm/°C Table 7.8. Internal Low-Frequency Oscillator Electrical Characteristics V =1.8 to 3.6V, –40 to +105°C (C8051F39x), –40 to +85°C (C8051F37x), using factory-calibrated settings, DD unless otherwise specified. Parameter Test Condition Min Typ Max Unit Oscillator Frequency C8051F390/1/2/3, 75 80 85 kHz C8051F370/1 Oscillator Supply Current C8051F394/5/6/7, — 5.5 12 µA (from VDD) C8051F374/5 Power Supply Sensitivity C8051F398/9 — 0.05 — %/V Temperature Sensitivity — 160 — ppm/°C Table 7.9. Internal Low-Power Oscillator Electrical Characteristics V =1.8 to 3.6V, –40 to +105°C (C8051F39x), –40 to +85°C (C8051F37x), using factory-calibrated settings, DD unless otherwise specified. Parameter Test Condition Min Typ Max Unit Oscillator Frequency C8051F390/1/2/3, 18.5 20 21.5 MHz C8051F370/1 Power Supply Sensitivity C8051F394/5/6/7, — 0.1 — %/V C8051F374/5 Temperature Sensitivity C8051F398/9 — 60 — ppm/°C 38 Rev. 1.2

C8051F39x/37x Table 7.10. ADC0 Electrical Characteristics V =3.0V, VREF=2.40V (REFSL=0), –40 to +105°C (C8051F39x), –40 to +85°C (C8051F37x), unless DD otherwise specified. Parameter Test Condition Min Typ Max Unit DC Accuracy Resolution C8051F394/5/6/7, C8051F374/5 10 bits Integral Nonlinearity C8051F398/9 — <±0.5 ±2.0 LSB Differential Nonlinearity — <±0.5 ±1 LSB Offset Error –2 0 2 LSB Full Scale Error –5 –2 1 LSB Offset Temperature Coefficient — 0.005 — LSB/°C Dynamic performance (10kHz sine-wave single-ended input, 1dB below Full Scale, 500ksps) Signal-to-Noise Plus Distortion 55 58 — dB Total Harmonic Distortion Up to the 5th harmonic — –73 — dB Spurious-Free Dynamic Range — 68 — dB Conversion Rate SAR Conversion Clock — — 8.33 MHz Conversion Time in SAR Clocks 13 — — clocks Track/Hold Acquisition Time 300 — — ns Throughput Rate — — 500 ksps Analog Inputs ADC Input Voltage Range Single Ended (AIN+ – GND) 0 — VREF V Differential (AIN+ – AIN–) –VREF — VREF V Absolute Pin Voltage with Single Ended or Differential 0 — V V DD respect to GND Sampling Capacitance — 5 — pF (C ) SAMPLE Input Multiplexer Impedance — 1.6 — k (R ) MUX Power Specifications Power Supply Current Operating Mode, 500ksps — 860 1010 µA (V supplied to ADC0) DD Power Supply Rejection Single Ended (AIN+ – GND) — 1.15 — mV/V Differential (AIN+ – AIN–) — 2.45 — mV/V Rev. 1.2 39

C8051F39x/37x Table 7.11. ADC Temperature Sensor Electrical Characteristics V =3.0V, –40 to +105°C (C8051F39x), –40 to +85°C (C8051F37x), unless otherwise specified. DD Parameter Test Condition Min Typ Max Unit Linearity — 0.75 — °C Slope — 2.92 — mV/°C Slope Error* — 70 — µV/°C Offset Temp=0°C — 785 — mV Offset Error* Temp=0°C — 13 — mV Supply Current — 90 120 µA Note: Represents one standard deviation from the mean. Table 7.12. Precision Temperature Sensor Electrical Characteristics V =1.8 to 3.6V, –40 to +105°C (C8051F39x), –40 to +85°C (C8051F37x), unless otherwise specified. DD Parameter Test Condition Min Typ Max Unit Range –40 — 105 °C Absolute Error –2 0.2 +2 °C Integral Nonlinearity — 0 ±0.4 °C Resolution 0.0078125 °C Power Supply Rejection — 0.05 0.2 °C/V Supply Current — 230 280 µA Clock Frequency (F ) 320 520 730 kHz TS0 40 Rev. 1.2

C8051F39x/37x Table 7.13. Voltage Reference Electrical Characteristics V =3.0V, –40 to +105°C (C8051F39x), –40 to +85°C (C8051F37x), unless otherwise specified. DD Parameter Test Condition Min Typ Max Unit Internal Reference (REFBE=1) Output Voltage 2.4V Setting 2.37 2.4 2.43 V 1.2V Setting 1.18 1.2 1.22 V VREF Short-Circuit Current — — 9 mA VREF Temperature — 33 — ppm/°C Coefficient Load Regulation Load=0 to 200µA to AGND — 6 — µV/µA VREF Turn-on Time 1 4.7µF tantalum, 0.1µF ceramic bypass — 1.5 — ms VREF Turn-on Time 2 0.1µF ceramic bypass — 110 — µs Power Supply Rejection 2.4V Setting — 3.5 — mV/V 1.2V Setting — 1.1 — mV/V External Reference (REFBE=0) Input Voltage Range 1.0 — V V DD Input Current Sample Rate=200ksps; VREF=3.0V — 3 — µA Power Specifications Supply Current REFBE=“1” or TEMPE=“1” — 70 100 µA Table 7.14. Voltage Regulator Electrical Characteristics V =3.0V, –40 to +105°C (C8051F39x), –40 to +85°C (C8051F37x), unless otherwise specified. DD Parameter Test Condition Min Typ Max Unit Output Voltage 1.73 1.78 1.83 V Power Supply Sensitivity Constant Temperature — 0.5 — %/V Temperature Sensitivity Constant Supply — 55 — ppm/°C Rev. 1.2 41

C8051F39x/37x Table 7.15. IDAC Electrical Characteristics V =3.0V, –40 to +105°C (C8051F39x), –40 to +85°C (C8051F37x), full-scale output current set to 2mA, DD unless otherwise specified. Parameter Test Condition Min Typ Max Unit Static Performance Resolution 10 bits Integral Nonlinearity — <±1 ±3 LSB Differential Nonlinearity 0 to +105°C, — <±0.5 ±1 LSB Guaranteed Monotonic –40 to 0°C –1.0 <±0.5 1.3 LSB Output Compliance Range 0 — V – 1.0 V DD Offset Error — 0 — µA Full Scale Error 2mA Full Scale Output Current –122 0 40 µA 1mA Full Scale Output Current –61 0 20 µA 0.5mA Full Scale Output Current –31 0 10 µA Full Scale Error Tempco — 80 — ppm/°C V Power Supply — 1.05 — µA/V DD Rejection Ratio Dynamic Performance Output Settling Time to 1/2 IDA0H:L=0x3FF to 0x000 — 7 — µs LSB Startup Time — 6.5 — µs Gain Variation 1mA Full Scale Output Current — 0.1 — % 0.5mA Full Scale Output Current — 0.1 — % Power Consumption Power Supply Current 2mA Full Scale Output Current — 2065 — µA (V supplied to IDAC) DD 1mA Full Scale Output Current — 1065 — µA 0.5mA Full Scale Output Current — 565 — µA 42 Rev. 1.2

C8051F39x/37x Table 7.16. Comparator Electrical Characteristics V =3.0V, –40 to +105°C (C8051F39x), –40 to +85°C (C8051F37x), unless otherwise specified. DD Parameter Test Condition Min Typ Max Unit Response Time CP0+ – CP0–=100mV — 370 — ns Mode 0, Vcm*=1.5V CP0+ – CP0–=–100mV — 135 — ns Response Time CP0+ – CP0–=100mV — 1575 — ns Mode 3, Vcm*=1.5V CP0+ – CP0–=–100mV — 3705 — ns Common-Mode Rejection Ratio — 0.6 5 mV/V Positive Hysteresis CP0HYP1–0=00 — 0.5 — mV Mode 0 (CPMD=00) CP0HYP1–0=01 — 8 — mV CP0HYP1–0=10 — 16 — mV CP0HYP1–0=11 — 32 — mV Negative Hysteresis CP0HYN1–0=00 — 0.5 — mV Mode 0 (CPMD=00) CP0HYN1–0=01 — –8 — mV CP0HYN1–0=10 — –16 — mV CP0HYN1–0=11 — –32 — mV Positive Hysteresis CP0HYP1–0=00 — 0.5 — mV Mode 1 (CPMD=01) CP0HYP1–0=01 — 6 — mV CP0HYP1–0=10 — 12 — mV CP0HYP1–0=11 — 24.5 — mV Negative Hysteresis CP0HYN1–0=00 — 0.5 — mV Mode 1 (CPMD=01) CP0HYN1–0=01 — –6 — mV CP0HYN1–0=10 — –12 — mV CP0HYN1–0=11 — –24.5 — mV Positive Hysteresis CP0HYP1–0=00 — 0.7 — mV Mode 2 (CPMD=10) CP0HYP1–0=01 — 4.5 — mV CP0HYP1–0=10 — 10 — mV CP0HYP1–0=11 — 19 — mV Negative Hysteresis CP0HYN1–0=00 — 0.7 — mV Mode 2 (CPMD=10) CP0HYN1–0=01 — –4.5 — mV CP0HYN1–0=10 — –10 — mV CP0HYN1–0=11 — –19 — mV Positive Hysteresis CP0HYP1–0=00 — 1.6 2.3 mV Mode 3 (CPMD=11) CP0HYP1–0=01 2 4 6 mV CP0HYP1–0=10 4.8 8 11 mV CP0HYP1–0=11 10 15.5 21 mV Rev. 1.2 43

C8051F39x/37x Table 7.16. Comparator Electrical Characteristics (Continued) V =3.0V, –40 to +105°C (C8051F39x), –40 to +85°C (C8051F37x), unless otherwise specified. DD Parameter Test Condition Min Typ Max Unit Negative Hysteresis CP0HYN1–0=00 — 1.6 2.3 mV Mode 3 (CPMD=11) CP0HYN1–0=01 –6 –4 –2 mV CP0HYN1–0=10 –11 –8 –4.8 mV CP0HYN1–0=11 –21 –15.5 –10 mV Inverting or Non-Inverting Input –0.25 — V + 0.25 V DD Voltage Range Input Capacitance — 4 — pF Input Bias Current — 0.001 — nA Input Offset Voltage 10 — –10 mV Power Supply Power Supply Rejection — 0.1 — mV/V Power-up Time — 6.5 — µs Supply Current at DC Mode 0 — 32 50 µA Mode 1 — 15 25 µA Mode 2 — 5 12 µA Mode 3 — 2 8 µA Note: Vcm is the common-mode voltage on CP0+ and CP0–. 44 Rev. 1.2

C8051F39x/37x 7.3. Typical Performance Curves VDD(cid:3)=(cid:3)1.8V VDD(cid:3)=(cid:3)3.0V VDD(cid:3)=(cid:3)3.6V 8.0 F < 9 MHz F > 9 MHz 7.0 Oneshot Oneshot Enabled Disabled 6.0 5.0 A) m 4.0 D((cid:3) D I 3.0 2.0 1.0 0.0 0 5 10 15 20 25 30 35 40 45 50 SYSCLK(cid:3)(MHz) Figure 7.1. Normal Mode Digital Supply Current vs. Frequency VDD(cid:3)=(cid:3)1.8V VDD(cid:3)=(cid:3)3.0V VDD(cid:3)=(cid:3)3.6V 4.0 3.5 3.0 2.5 A) m 2.0 D((cid:3) D I 1.5 1.0 0.5 0.0 0 5 10 15 20 25 30 35 40 45 50 SYSCLK(cid:3)(MHz) Figure 7.2. Idle Mode Digital Supply Current vs. Frequency Rev. 1.2 45

C8051F39x/37x 2.00 1.75 1.50 1.25 1.00 0.75 0.50 0.25 C)(cid:3) or(°(cid:3) 0.00 Err (cid:882)0.25 (cid:882)0.50 (cid:882)0.75 (cid:882)1.00 (cid:882)1.25 (cid:882)1.50 (cid:882)1.75 (cid:882)2.00 (cid:882)40 (cid:882)35 (cid:882)30 (cid:882)25 (cid:882)20 (cid:882)15 (cid:882)10 (cid:882)5 0 5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80 85 90 95 100 105 Temperature(cid:3)(°C)(cid:3) Figure 7.3. Precision Temperature Sensor Error vs. Temperature 46 Rev. 1.2

C8051F39x/37x 8. Precision Temperature Sensor (C8051F390/2/4/6/8 and C8051F370/4 Only) The precision temperature sensor is a self-contained module that reports the die temperature in degrees Celsius. For the temperature sensor accessed by the ADC, refer to Section 10. The precision temperature sensor begins a conversion once the TS0STRT bit is set to 1 then cleared to 0 by firmware. The conversion length is specified by TS0CNVL, with a longer conversion time resulting in a more accurate temperature measurement. The TS0DN bit is set by hardware once the temperature sensor block has completed the measurement, and the temperature is available in TS0DATH:TS0DATL. The precision temperature sensor may also be enabled as an interrupt source by setting the EPTS bit in EIE2. When enabled, the interrupt occurs once TS0DN is set to 1 by hardware. 8.1. Temperature in Two’s Complement The 16-bit word in TS0DATH:TS0DATL is the temperature in degrees Celsius represented in two's com- plement with 1 weighted sign bit, 8 integer bits, and 7 fractional bits. Equation8.1 converts the value in TS0DATH:TS0DATL from two’s complement binary to decimal.  6 7  Temperature in C = –TS0DATH728+  TS0DATHn2n+1+  TS0DATLn2n–7     n=0 n=0 Equation8.1.Temperature Conversion from Two’s Complement Binary to Decimal Where:  TS0DATH[n] is the nth bit in TS0DATH  TS0DATL[n] is the nth bit in TS0DATL Table8.1 lists several 16-bit values in TS0DATH:TS0DATL and the corresponding temperature. Table 8.1. Example Temperature Values in TS0DATH:TS0DATL Hexadecimal Binary Temperature (°C) 0x3480 0011 0100 1000 0000 105 0x1400 0001 0100 0000 0000 40 0x0CE0 0000 1100 1110 0000 25.75 0x0080 0000 0000 1000 0000 1 0x0040 0000 0000 0100 0000 0.5 0x0001 0000 0000 0000 0001 1/128 0x0000 0000 0000 0000 0000 0 0xFFFF 1111 1111 1111 1111 –1/128 0xFFC0 1111 1111 1100 0000 –0.5 0xFF80 1111 1111 1000 0000 –1 0xF320 1111 0011 0010 0000 –25.75 0xEC00 1110 1100 0000 0000 –40 Rev. 1.2 47

C8051F39x/37x SFR Definition 8.1. TS0CN: Temperature Sensor Control Bit 7 6 5 4 3 2 1 0 Name TS0STRT TS0DN TS0CNVL Type R/W R R/W R/W R/W R/W Reset 0 0 0 0 0 0 0 0 SFR Address=0xD2; SFR Page=F Bit Name Function 7 TS0STRT Temperature Sensor Start. Firmware must set this bit to 1, then clear this bit to 0 to start a temperature sensor measurement. 6 TS0DN Temperature Sensor Finished Flag. Hardware will set TS0DN to 1 when a temperature sensor measurement is com- plete. If enabled, a temperature sensor interrupt will be generated. This bit must be cleared to 0 by firmware. 5:3 Reserved Must Write 000b. 2:0 TS0CNVL Temperature Sensor Conversion Length. This field sets the conversion length of time over which the temperature is calcu- lated. A longer conversion length results in a more accurate measurement. The conversion length in microseconds is derived from the following equation, where TS0CNVL is the 3-bit value held in TS0CNVL[2:0] and F is the precision tem- TS0 perature sensor clock frequency given in Table7.12. Conversion Length in s = --2---5---6---106 2TS0CNVL+1+1+32 F  TS0 48 Rev. 1.2

C8051F39x/37x SFR Definition 8.2. TS0DATH: Temperature Sensor Output High Byte Bit 7 6 5 4 3 2 1 0 Name TS0DATH Type R/W Reset 0 0 0 0 0 0 0 0 SFR Address=0xD3; SFR Page=0 Bit Name Function 7:0 TS0DATH Temperature Sensor Data Word (MSB). This byte represents the MSB of the temperature sensor data word. The data word is a 16-bit, 2’s complement num- ber. SFR Definition 8.3. TS0DATL: Temperature Sensor Output Low Byte Bit 7 6 5 4 3 2 1 0 Name TS0DATL Type R/W Reset 0 0 0 0 0 0 0 0 SFR Address=0xD2; SFR Page=0 Bit Name Function 7:0 TS0DATL Temperature Sensor Data Word (LSB). This byte represents the LSB of the temperature sensor data word. The data word is a 16-bit, 2’s complement num- ber. Rev. 1.2 49

C8051F39x/37x 9. 10-Bit ADC (ADC0, C8051F390/2/4/6/8 and C8051F370/4 Only) ADC0 on the C8051F390/2/4/6/8 and C8051F370/4 is a 500ksps, 10-bit successive-approximation-regis- ter (SAR) ADC with integrated track-and-hold and a programmable window detector. The ADC is fully con- figurable under software control via Special Function Registers. The ADC may be configured to measure various different signals using the analog multiplexer described in Section “9.4.ADC0 Analog Multiplexer (C8051F390/2/4/6/8 and C8051F370/4 Only)” on page61. The voltage reference for the ADC is selected as described in Section “12.Voltage Reference Options” on page73. The ADC0 subsystem is enabled only when the AD0EN bit in the ADC0 Control register (ADC0CN) is set to logic1. The ADC0 subsystem is in low power shutdown when this bit is logic0. AMX0P ADC0CN AMX0P5AMX0P4AMX0P3AMX0P2AMX0P1AMX0P0 AD0ENAD0TMAD0INTAD0BUSYAD0WINTAD0CM2AD0CM1AD0CM0 Port I/O Pins* VDD 000 AD0BUSY (W) Positive Start 001 Timer 0 Overflow Conversion Input 010 Timer 2 Overflow VDD (AIN+) 011 Timer 1 Overflow AMUX 100 CNVSTR Input Temp 10-Bit C0L 101 Timer 3 Overflow Sensor D 110 Timer 4 Overflow AIN+ SAR A 111 Timer 5 Overflow AIN- ADC H 0 C Port I/O D Pins* A Negative KF VREF (IAnIpNu-t) YSCLRE AD0WINT AMUX S GND Window Compare N5N4N3N2N1N0 C4C3C2C1C0ST 32 Logic MX0MX0MX0MX0MX0MX0 D0SD0SD0SD0SD0SD0LJ ADC0LTH ADC0LTL AAAAAA AAAAAA * 20 Selections on 24-pin package AMX0N ADC0CF ADC0GTH ADC0GTL 16 Selections on 20-pin package Figure 9.1. ADC0 Functional Block Diagram 50 Rev. 1.2

C8051F39x/37x 9.1. Output Code Formatting The conversion code format differs between Single-ended and Differential modes. The registers ADC0H and ADC0L contain the high and low bytes of the output conversion code from the ADC at the completion of each conversion. Data can be right-justified or left-justified, depending on the setting of the AD0LJST bit (ADC0CN.0). When in Single-ended Mode, conversion codes are represented as 10-bit unsigned integers. Inputs are measured from 0 to VREF x 1023/1024. Example codes are shown below for both right-justified and left-justified data. Unused bits in the ADC0H and ADC0L registers are set to 0. Input Voltage Right-Justified ADC0H:ADC0L Left-Justified ADC0H:ADC0L (Single-Ended) (AD0LJST=0) (AD0LJST=1) VREF x 1023/1024 0x03FF 0xFFC0 VREF x 512/1024 0x0200 0x8000 VREF x 256/1024 0x0100 0x4000 0 0x0000 0x0000 When in Differential Mode, conversion codes are represented as 10-bit signed 2s complement numbers. Inputs are measured from –VREF to VREF x 511/512. Example codes are shown below for both right-jus- tified and left-justified data. For right-justified data, the unused MSBs of ADC0H are a sign-extension of the data word. For left-justified data, the unused LSBs in the ADC0L register are set to 0. Input Voltage Right-Justified ADC0H:ADC0L Left-Justified ADC0H:ADC0L (Differential) (AD0LJST=0) (AD0LJST=1) VREF x 511/512 0x01FF 0x7FC0 VREF x 256/512 0x0100 0x4000 0 0x0000 0x0000 –VREF x 256/512 0xFF00 0xC000 –VREF 0xFE00 0x8000 Rev. 1.2 51

C8051F39x/37x 9.2. Modes of Operation ADC0 has a maximum conversion speed of 500ksps. The ADC0 conversion clock is a divided version of the system clock, determined by the AD0SC bits in the ADC0CF register. 9.2.1. Starting a Conversion A conversion can be initiated in one of several ways, depending on the programmed states of the ADC0 Start of Conversion Mode bits (AD0CM2–0) in register ADC0CN. Conversions may be initiated by one of the following: 1. Writing a 1 to the AD0BUSY bit of register ADC0CN 2. A Timer0 overflow (i.e., timed continuous conversions) 3. A Timer2 overflow 4. A Timer1 overflow 5. A rising edge on the CNVSTR input signal 6. A Timer3 overflow 7. A Timer4 overflow 8. A Timer5 overflow Writing a 1 to AD0BUSY provides software control of ADC0 whereby conversions are performed "on- demand". During conversion, the AD0BUSY bit is set to logic1 and reset to logic0 when the conversion is complete. The falling edge of AD0BUSY triggers an interrupt (when enabled) and sets the ADC0 interrupt flag (AD0INT). Note: When polling for ADC conversion completions, the ADC0 interrupt flag (AD0INT) should be used. Converted data is available in the ADC0 data registers, ADC0H:ADC0L, when bit AD0INT is logic1. Note that when Timer 2, 3, 4, or 5 overflows are used as the conversion source, Low Byte over- flows are used if the timer is in 8-bit mode; High byte overflows are used if the timer is in 16-bit mode. See Section “31.Timers” on page242 for timer configuration. Important Note About Using CNVSTR: The CNVSTR input pin also functions as a Port I/O pin. When the CNVSTR input is used as the ADC0 conversion source, the associated pin should be skipped by the Digi- tal Crossbar. See Section “27.Port Input/Output” on page173 for details on Port I/O configuration. 52 Rev. 1.2

C8051F39x/37x 9.2.2. Tracking Modes The AD0TM bit in register ADC0CN controls the ADC0 track-and-hold mode. In its default state, the ADC0 input is continuously tracked, except when a conversion is in progress. When the AD0TM bit is logic 1, ADC0 operates in low-power track-and-hold mode. In this mode, each conversion is preceded by a track- ing period of three SAR clocks (after the start-of-conversion signal). When the CNVSTR signal is used to initiate conversions in low-power tracking mode, ADC0 tracks only when CNVSTR is low; conversion begins on the rising edge of CNVSTR. See Figure9.2 for track and convert timing details. Tracking can also be disabled (shutdown) when the device is in low power standby or sleep modes. Low-power track- and-hold mode is also useful when AMUX settings are frequently changed, due to the settling time require- ments described in Section “9.2.3.Settling Time Requirements” on page54. A. ADC0 Timing for External Trigger Source CNVSTR (AD0CM[2:0]=100) 1 1 1 2 3 4 5 6 7 8 9 0 1 SAR Clocks Low Power Low Power AD0TM=1 Track Convert or Convert Mode AD0TM=0 Track or Convert Convert Track B. ADC0 Timing for Internal Trigger Source Write '1' to AD0BUSY, Timer 0, Timer 2, Timer 1, Timer 3 Overflow (AD0CM[2:0]=000, 001,010 011, 101) 1 1 1 1 1 1 2 3 4 5 6 7 8 9 SAR 0 1 2 3 4 Clocks Low Power AD0TM=1 Track Convert Low Power Mode or Convert 1 1 1 2 3 4 5 6 7 8 9 SAR 0 1 Clocks Track or AD0TM=0 Convert Track Convert Figure 9.2. 10-Bit ADC Track and Conversion Example Timing Rev. 1.2 53

C8051F39x/37x 9.2.3. Settling Time Requirements A minimum tracking time is required before each conversion to ensure that an accurate conversion is per- formed. This tracking time is determined by the AMUX0 resistance, the ADC0 sampling capacitance, any external source resistance, and the accuracy required for the conversion. Note that in low-power tracking mode, three SAR clocks are used for tracking at the start of every conversion. For most applications, these three SAR clocks will meet the minimum tracking time requirements. Figure9.3 shows the equivalent ADC0 input circuit. The required ADC0 settling time for a given settling accuracy (SA) may be approximated by Equation9.1. See Table7.10 for ADC0 minimum settling time requirements as well as the mux impedance and sampling capacitor values. n 2  t = ln -------  R C SA TOTAL SAMPLE Equation 9.1. ADC0 Settling Time Requirements Where: SA is the settling accuracy, given as a fraction of an LSB (for example, 0.25 to settle within 1/4 LSB) t is the required settling time in seconds R is the sum of the AMUX0 resistance and any external source resistance. TOTAL n is the ADC resolution in bits (10). Differential Mode Single-Ended Mode MUX MUX Select Select Px.x Px.x RMUX RMUX CSAMPLE CSAMPLE RCInput= RMUX* CSAMPLE RCInput= RMUX* CSAMPLE CSAMPLE Px.x RMUX MUX Select Figure 9.3. ADC0 Equivalent Input Circuits 54 Rev. 1.2

C8051F39x/37x SFR Definition 9.1. ADC0CF: ADC0 Configuration Bit 7 6 5 4 3 2 1 0 Name AD0SC[4:0] AD0LJST Type R/W R/W R/W Reset 1 1 1 1 1 0 0 0 SFR Address=0xBC; SFR Page=All Pages Bit Name Function 7:3 AD0SC[4:0] ADC0 SAR Conversion Clock Period Bits. SAR Conversion clock is derived from system clock by the fol- lowing equation, where AD0SC refers to the 5-bit value held in bits AD0SC4–0. SAR Conversion clock requirements are given in the ADC specification Table7.10. SYSCLK AD0SC = ----------------------- –1 CLK SAR 2 AD0LJST ADC0 Left Justify Select. 0: Data in ADC0H:ADC0L registers are right-justified. 1: Data in ADC0H:ADC0L registers are left-justified. 1:0 Reserved Must Write 00b. Rev. 1.2 55

C8051F39x/37x SFR Definition 9.2. ADC0H: ADC0 Data Word MSB Bit 7 6 5 4 3 2 1 0 Name ADC0H[7:0] Type R/W Reset 0 0 0 0 0 0 0 0 SFR Address=0xBE; SFR Page=All Pages Bit Name Function 7:0 ADC0H[7:0] ADC0 Data Word High-Order Bits. For AD0LJST=0: Bits 7–2 will read 000000b. Bits 1–0 are the upper 2 bits of the 10-bit ADC0 Data Word. For AD0LJST=1: Bits 7–0 are the most-significant bits of the 10-bit ADC0 Data Word. SFR Definition 9.3. ADC0L: ADC0 Data Word LSB Bit 7 6 5 4 3 2 1 0 Name ADC0L[7:0] Type R/W Reset 0 0 0 0 0 0 0 0 SFR Address=0xBD; SFR Page=All Pages Bit Name Function 7:0 ADC0L[7:0] ADC0 Data Word Low-Order Bits. For AD0LJST=0: Bits 7–0 are the lower 8 bits of the 10-bit Data Word. For AD0LJST=1: Bits 7–6 are the lower 2 bits of the 10-bit Data Word. Bits 5– 0 will read 000000b. 56 Rev. 1.2

C8051F39x/37x SFR Definition 9.4. ADC0CN: ADC0 Control Bit 7 6 5 4 3 2 1 0 Name AD0EN AD0TM AD0INT AD0BUSY AD0WINT AD0CM[2:0] Type R/W R/W R/W R/W R/W R/W Reset 0 0 0 0 0 0 0 0 SFR Address=0xE8; SFR Page=All Pages; Bit-Addressable Bit Name Function 7 AD0EN ADC0 Enable Bit. 0: ADC0 Disabled. ADC0 is in low-power shutdown. 1: ADC0 Enabled. ADC0 is active and ready for data conversions. 6 AD0TM ADC0 Track Mode Bit. 0: Normal Track Mode: When ADC0 is enabled, tracking is continuous unless a con- version is in progress. Conversion begins immediately on start-of-conversion event, as defined by AD0CM[2:0]. 1: Delayed Track Mode: When ADC0 is enabled, input is tracked when a conversion is not in progress. A start-of-conversion signal initiates three SAR clocks of additional tracking, and then begins the conversion. Note that there is not a tracking delay when CNVSTR is used (AD0CM[2:0]=100). 5 AD0INT ADC0 Conversion Complete Interrupt Flag. 0: ADC0 has not completed a data conversion since AD0INT was last cleared. 1: ADC0 has completed a data conversion. 4 AD0BUSY ADC0 Busy Bit. 3 AD0WINT ADC0 Window Compare Interrupt Flag. 0: ADC0 Window Comparison Data match has not occurred since this flag was last cleared. 1: ADC0 Window Comparison Data match has occurred. 2:0 AD0CM[2: ADC0 Start of Conversion Mode Select. 0] 000: ADC0 start-of-conversion source is write of 1 to AD0BUSY. 001: ADC0 start-of-conversion source is overflow of Timer0. 010: ADC0 start-of-conversion source is overflow of Timer2. 011: ADC0 start-of-conversion source is overflow of Timer1. 100: ADC0 start-of-conversion source is rising edge of external CNVSTR. 101: ADC0 start-of-conversion source is overflow of Timer3. 110: ADC0 start-of-conversion source is overflow of Timer4. 111: ADC0 start-of-conversion source is overflow of Timer5. Rev. 1.2 57

C8051F39x/37x 9.3. Programmable Window Detector The ADC Programmable Window Detector continuously compares the ADC0 output registers to user-pro- grammed limits, and notifies the system when a desired condition is detected. This is especially effective in an interrupt-driven system, saving code space and CPU bandwidth while delivering faster system response times. The window detector interrupt flag (AD0WINT in register ADC0CN) can also be used in polled mode. The ADC0 Greater-Than (ADC0GTH, ADC0GTL) and Less-Than (ADC0LTH, ADC0LTL) registers hold the comparison values. The window detector flag can be programmed to indicate when mea- sured data is inside or outside of the user-programmed limits, depending on the contents of the ADC0 Less-Than and ADC0 Greater-Than registers. SFR Definition 9.5. ADC0GTH: ADC0 Greater Than Data High Byte Bit 7 6 5 4 3 2 1 0 Name ADC0GTH[7:0] Type R/W Reset 1 1 1 1 1 1 1 1 SFR Address=0xC4; SFR Page=All Pages Bit Name Function 7:0 ADC0GTH[7:0] ADC0 Greater-Than Data Word High-Order Bits. SFR Definition 9.6. ADC0GTL: ADC0 Greater-Than Data Low Byte Bit 7 6 5 4 3 2 1 0 Name ADC0GTL[7:0] Type R/W Reset 1 1 1 1 1 1 1 1 SFR Address=0xC3; SFR Page=All Pages Bit Name Function 7:0 ADC0GTL[7:0] ADC0 Greater-Than Data Word Low-Order Bits. 58 Rev. 1.2

C8051F39x/37x SFR Definition 9.7. ADC0LTH: ADC0 Less-Than Data High Byte Bit 7 6 5 4 3 2 1 0 Name ADC0LTH[7:0] Type R/W Reset 0 0 0 0 0 0 0 0 SFR Address=0xC6; SFR Page=All Pages Bit Name Function 7:0 ADC0LTH[7:0] ADC0 Less-Than Data Word High-Order Bits. SFR Definition 9.8. ADC0LTL: ADC0 Less-Than Data Low Byte Bit 7 6 5 4 3 2 1 0 Name ADC0LTL[7:0] Type R/W Reset 0 0 0 0 0 0 0 0 SFR Address=0xC5; SFR Page=All Pages Bit Name Function 7:0 ADC0LTL[7:0] ADC0 Less-Than Data Word Low-Order Bits. Rev. 1.2 59

C8051F39x/37x 9.3.1. Window Detector Example Figure9.4 shows two example window comparisons for right-justified, single-ended data, with ADC0LTH:ADC0LTL=0x0080 (128d) and ADC0GTH:ADC0GTL=0x0040 (64d). The input voltage can range from 0 to VREF x (1023/1024) with respect to GND, and is represented by a 10-bit unsigned integer value. In the left example, an AD0WINT interrupt will be generated if the ADC0 conversion word (ADC0H:ADC0L) is within the range defined by ADC0GTH:ADC0GTL and ADC0LTH:ADC0LTL (if0x0040<ADC0H:ADC0L<0x0080). In the right example, and AD0WINT interrupt will be generated if the ADC0 conversion word is outside of the range defined by the ADC0GT and ADC0LT registers (ifADC0H:ADC0L<0x0040 or ADC0H:ADC0L>0x0080). Figure9.5 shows an example using left-justi- fied data with the same comparison values. ADC0H:ADC0L ADC0H:ADC0L Input Voltage Input Voltage (AIN - GND) (AIN - GND) VREF x (1023/ 0x03FF VREF x (1023/ 0x03FF 1024) 1024) AD0WINT AD0WINT=1 not affected 0x0081 0x0081 VREF x (128/1024) 0x0080 ADC0LTH:ADC0LTL VREF x (128/1024) 0x0080 ADC0GTH:ADC0GTL 0x007F 0x007F AD0WINT AD0WINT=1 not affected 0x0041 0x0041 VREF x (64/1024) 0x0040 ADC0GTH:ADC0GTL VREF x (64/1024) 0x0040 ADC0LTH:ADC0LTL 0x003F 0x003F AD0WINT AD0WINT=1 not affected 0 0x0000 0 0x0000 Figure 9.4. ADC Window Compare Example: Right-Justified, Single-Ended Data ADC0H:ADC0L ADC0H:ADC0L Input Voltage Input Voltage (AIN - GND) (AIN - GND) VREF x (1023/ 0xFFC0 VREF x (1023/ 0xFFC0 1024) 1024) AD0WINT AD0WINT=1 not affected 0x2040 0x2040 VREF x (128/1024) 0x2000 ADC0LTH:ADC0LTL VREF x (128/1024) 0x2000 ADC0GTH:ADC0GTL 0x1FC0 0x1FC0 AD0WINT AD0WINT=1 not affected 0x1040 0x1040 VREF x (64/1024) 0x1000 ADC0GTH:ADC0GTL VREF x (64/1024) 0x1000 ADC0LTH:ADC0LTL 0x0FC0 0x0FC0 AD0WINT AD0WINT=1 not affected 0 0x0000 0 0x0000 Figure 9.5. ADC Window Compare Example: Left-Justified, Single-Ended Data 60 Rev. 1.2

C8051F39x/37x 9.4. ADC0 Analog Multiplexer (C8051F390/2/4/6/8 and C8051F370/4 Only) ADC0 on the C8051F390/2/4/6/8 and C8051F370/4 has two analog multiplexers, referred to collectively as AMUX0. AMUX0 selects the positive and negative inputs to the ADC. Any of the following may be selected as the positive input: Port I/O pins, the on-chip temperature sensor, or the positive power supply (V ). Any of the DD following may be selected as the negative input: Port I/O pins, V , or GND. When GND is selected as REF the negative input, ADC0 operates in Single-ended Mode; all other times, ADC0 operates in Differ- ential Mode. The ADC0 input channels are selected in the AMX0P and AMX0N registers as described in SFR Definition 9.9 and SFR Definition 9.10. P0.0 AMX0P 4 3 2 1 0 P P P P P 0 0 0 0 0 X X X X X M M M M M A A A A A AMUX P2.3* Temp Sensor VDD AIN+ ADC0 P0.0 AIN- AMUX AMX0N 4 3 2 1 0 P2.3* N N N N N 0 0 0 0 0 X X X X X VREF AM AM AM AM AM GND *P2.0-P2.3 Only available as inputs on QFN24 Packaging Figure 9.6. ADC0 Multiplexer Block Diagram Important Note About ADC0 Input Configuration: Port pins selected as ADC0 inputs should be config- ured as analog inputs, and should be skipped by the Digital Crossbar. To configure a Port pin for analog input, set to ‘0’ the corresponding bit in register PnMDIN. To force the Crossbar to skip a Port pin, set to ‘1’ the corresponding bit in register PnSKIP. See Section “27.Port Input/Output” on page173 for more Port I/ O configuration details. Rev. 1.2 61

C8051F39x/37x SFR Definition 9.9. AMX0P: AMUX0 Positive Channel Select Bit 7 6 5 4 3 2 1 0 Name AMX0P[4:0] Type R R R R/W Reset 0 0 0 1 1 1 1 1 SFR Address=0xBB; SFR Page=All Pages Bit Name Function 7:5 Unused Read=000b; Write=Don’t Care. 4:0 AMX0P[4:0] AMUX0 Positive Input Selection. 00000: P0.0 00001: P0.1 00010: P0.2 00011: P0.3 00100: P0.4 00101: P0.5 00110: P0.6 00111: P0.7 01000: P1.0 01001: P1.1 01010: P1.2 01011: P1.3 01100: P1.4 01101: P1.5 01110: P1.6 01111: P1.7 10000: Temp Sensor 10001: V DD 10010: P2.0 (C8051F390/1/4/5 and C8051F37x Only) 10011: P2.1 (C8051F390/1/4/5 and C8051F37x Only) 10100: P2.2 (C8051F390/1/4/5 and C8051F37x Only) 10101: P2.3 (C8051F390/1/4/5 and C8051F37x Only) 10110 – 11111: no input selected 62 Rev. 1.2

C8051F39x/37x SFR Definition 9.10. AMX0N: AMUX0 Negative Channel Select Bit 7 6 5 4 3 2 1 0 Name AMX0N[4:0] Type R R R R/W Reset 0 0 0 1 1 1 1 1 SFR Address=0xBA; SFR Page=All Pages Bit Name Function 7:5 Unused Read=000b; Write=Don’t Care. 4:0 AMX0N[4:0] AMUX0 Negative Input Selection. 00000: P0.0 00001: P0.1 00010: P0.2 00011: P0.3 00100: P0.4 00101: P0.5 00110: P0.6 00111: P0.7 01000: P1.0 01001: P1.1 01010: P1.2 01011: P1.3 01100: P1.4 01101: P1.5 01110: P1.6 01111: P1.7 10000: V REF 10001: GND (ADC in Single-Ended Mode) 10010: P2.0 (C8051F390/1/4/5 and C8051F37x Only) 10011: P2.1 (C8051F390/1/4/5 and C8051F37x Only) 10100: P2.2 (C8051F390/1/4/5 and C8051F37x Only) 10101: P2.3 (C8051F390/1/4/5 and C8051F37x Only) 10110 – 11111: no input selected Rev. 1.2 63

C8051F39x/37x 10. Temperature Sensor (C8051F390/2/4/6/8 and C8051F370/4 Only) A fully C8051F33x-compatible temperature sensor is included on the C8051F390/2/4/6/8 and C8051F370/ 4 and accessed via the ADC multiplexer in single-ended configuration. For the self-contained precision temperature sensor, refer to Section 8. To use the ADC to measure the temperature sensor, the ADC mux channel should be configured to con- nect to the temperature sensor. The temperature sensor transfer function is shown in Figure10.1. The out- put voltage (V ) is the positive ADC input when the ADC multiplexer is set correctly. The TEMPE bit in TEMP register REF0CN enables/disables the temperature sensor, as described in SFR Definition 12.1. While dis- abled, the temperature sensor defaults to a high impedance state and any ADC measurements performed on the sensor will result in meaningless data. Refer to Table7.11 for the slope and offset parameters of the temperature sensor. V = (Slope x Temp ) + Offset TEMP C Temp = (V - Offset) / Slope C TEMP Slope (V / deg C) e g a t l o Offset (V at 0 Celsius) V Temperature Figure 10.1. Temperature Sensor Transfer Function 64 Rev. 1.2

C8051F39x/37x 10.1. Calibration The uncalibrated temperature sensor output is extremely linear and suitable for relative temperature mea- surements (see Table7.11 on page40 for specifications). For absolute temperature measurements, offset and/or gain calibration is recommended. Figure10.2 shows the typical temperature sensor error assuming a 1-point calibration at 0°C. Parame- ters that affect ADC measurement, in particular the voltage reference value, will also affect tem- perature measurement. 5.00 5.00 4.00 4.00 3.00 3.00 2.00 2.00 C) s 1.00 1.00 e e r g e0.00 0.00 d -40.00 -20.00 0.00 20.00 40.00 60.00 80.00 r ( o r-1.00 -1.00 r E -2.00 -2.00 -3.00 -3.00 -4.00 -4.00 -5.00 -5.00 Temperature (degrees C) Figure 10.2. Temperature Sensor Error with 1-Point Calibration at 0 °C Rev. 1.2 65

C8051F39x/37x 11. 10-Bit Current Mode DACs (IDA0, IDA1, C8051F390/2/4/6/8 and C8051F370/4 Only) The C8051F390/2/4/6/8 and C8051F370/4 devices include two 10-bit current-mode Digital-to-Analog Con- verters (IDACs). The maximum current output of the IDACs can be adjusted for three different current set- tings; 0.5mA, 1mA, and 2mA. The IDACs are enabled or disabled with the IDAnEN bit in the Control Register for that IDAC (see SFR Definition 11.1 and SFR Definition 11.4). When IDAnEN is set to 0, the IDAC output behaves as a normal GPIO pin. When IDAnEN is set to 1, the digital output drivers and weak pullup for the IDAC pin are automatically disabled, and the pin is connected to the IDAC output. An internal bandgap bias generator is used to generate a reference current for the IDAC whenever it is enabled. When using an IDAC, the crossbar skip functionality should be enabled on the IDAC output pin, to force the Crossbar to skip the output pin. 11.1. IDAC Output Scheduling The IDACs feature a flexible output update mechanism which allows for seamless full-scale changes and supports jitter-free updates for waveform generation. Three update modes are provided, allowing IDAC output updates on a write to IDAnH, on a Timer overflow, or on an external pin edge. 11.1.1. Update Output On-Demand In its default mode (IDAnCN.[6:4]=111) the IDAC output is updated “on-demand” on a write to the high- byte of the IDAC data register (IDAnH). It is important to note that writes to IDAnL are held in this mode, and have no effect on the IDAC output until a write to IDAnH takes place. If writing a full 10-bit word to the IDAC data registers, the 10-bit data word is written to the low byte (IDAnL) and high byte (IDAnH) data reg- isters. Data is latched into the IDAC after a write to the IDAnH register, so the write sequence should be IDAnL followed by IDAnH if the full 10-bit resolution is required. The IDAC can be used in 8-bit mode by initializing IDAnL to the desired value (typically 0x00), and writing data to only IDAnH (see Section 11.3 for information on the format of the 10-bit IDAC data word within the 16-bit SFR space). H 0 1 2 3 R 0 r r r r T IDA0EN DA me me me me VS IDA0CM2 I Ti Ti Ti Ti N C IDA0CM1 N C IDA0CM0 0 A D I IDA0OMD1 IDA0OMD0 H 8 0 A D 10 I IDA0 IDA0 h c at L L 2 0 A D I Figure 11.1. IDA0 Functional Block Diagram 66 Rev. 1.2

C8051F39x/37x H 0 5 2 3 R 1 r r r r T IDA1EN DA me me me me VS IDA1CM2 I Ti Ti Ti Ti N C IDA1CM1 N C IDA1CM0 1 A D I IDA1OMD1 IDA1OMD0 H 8 1 A D 10 I IDA1 IDA1 h c at L L 2 1 A D I Figure 11.2. IDA1 Functional Block Diagram Rev. 1.2 67

C8051F39x/37x 11.1.2. Update Output Based on Timer Overflow The IDAC outputs can use a Timer overflow to schedule an output update event. This feature is useful in systems where the IDAC is used to generate a waveform of a defined sampling rate by eliminating the effects of variable interrupt latency and instruction execution on the timing of the IDAC output. When the IDAnCM bits (IDAnCN.[6:4]) are set to 000, 001, 010 or 011, writes to both IDAC data registers (IDAnL and IDAnH) are held until an associated Timer overflow event occurs, at which time the IDAnH:IDAnL contents are copied to the IDAC input latches, allowing the IDAC output to change to the new value. 11.1.3. Update Output Based on CNVSTR Edge The IDAC output can also be configured to update on a rising edge, falling edge, or both edges of the external CNVSTR signal. When the IDAnCM bits (IDAnCN.[6:4]) are set to 100, 101, or 110, writes to both IDAC data registers (IDAnL and IDAnH) are held until an edge occurs on the CNVSTR input pin. The par- ticular setting of the IDAnCM bits determines whether IDAC outputs are updated on rising, falling, or both edges of CNVSTR. When a corresponding edge occurs, the IDAnH:IDAnL contents are copied to the IDAC input latches, allowing the IDAC output to change to the new value. 11.2. IDAC Reset Behavior By default, both IDAC modules revert to a disabled state on any reset source. It is possible to keep the IDAC outputs enabled through all but a POR or VDD monitor reset, however. When the IDAnRP bit in the IDAnCN register is set to 1, any reset other than a POR or VDD monitor reset will not affect the IDAC out- put. The IDAC output will remain enabled and the value in the IDAC output word is maintained. 11.3. IDAC Output Mapping The IDAC data registers (IDAnH and IDAnL) are left-justified, meaning that the eight MSBs of the IDAC output word are mapped to bits 7–0 of the IDAnH register, and the two LSBs of the IDAC output word are mapped to bits 7 and 6 of the IDAnL register. The data word mapping for the IDACs is shown in Figure11.3. IDAnH IDAnL B9 B8 B7 B6 B5 B4 B3 B2 B1 B0 Input Data Word Output Current Output Current Output Current (IDAn9–IDAn0) IDAnOMD[1:0]=1x IDAnOMD[1:0]=01 IDAnOMD[1:0]=00 0x000 0 mA 0 mA 0 mA 0x001 1/1024 x 2 mA 1/1024 x 1 mA 1/1024 x 0.5 mA 0x200 512/1024 x 2 mA 512/1024 x 1 mA 512/1024 x 0.5 mA 0x3FF 1023/1024 x 2 mA 1023/1024 x 1 mA 1023/1024 x 0.5 mA Figure 11.3. IDA0 Data Word Mapping The full-scale output current of the IDAC is selected using the IDAnOMD bits (IDAnCN[1:0]). By default, the IDAC is set to a full-scale output current of 2mA. The IDAnOMD bits can also be configured to provide full-scale output currents of 1mA or 0.5mA, as shown in SFR Definition 11.1 and SFR Definition 11.4. 68 Rev. 1.2

C8051F39x/37x SFR Definition 11.1. IDA0CN: IDA0 Control Bit 7 6 5 4 3 2 1 0 Name IDA0EN IDA0CM[2:0] IDA0RP IDA0OMD[1:0] Type R/W R/W R R/W R/W Reset 0 1 1 1 0 Varies 1 0 SFR Address=0xB9; SFR Page=0 Bit Name Function 7 IDA0EN IDA0 Enable. 0: IDA0 Disabled. 1: IDA0 Enabled. 6:4 IDA0CM[2:0] IDA0 Update Source Select bits. 000: DAC output updates on Timer0 overflow. 001: DAC output updates on Timer1 overflow. 010: DAC output updates on Timer2 overflow. 011: DAC output updates on Timer3 overflow. 100: DAC output updates on rising edge of CNVSTR. 101: DAC output updates on falling edge of CNVSTR. 110: DAC output updates on any edge of CNVSTR. 111: DAC output updates on write to IDA0H. 3 Reserved Write=0b. 2 IDA0RP IDA0 Reset Persistence. 0: IDA0 is disabled by any reset source. 1: IDA0 will remain enabled through any reset source except a power-on-reset. This bit is reset to 0 by a power on reset, but is sticky through all other reset sources. When setting IDA0RP to 1, IDA0EN must be set to 1 also in the same mov instruction. 1:0 IDA0OMD[1:0] IDA0 Output Mode Select bits. 00: 0.5mA full-scale output current. 01: 1.0mA full-scale output current. 1x: 2.0mA full-scale output current. Rev. 1.2 69

C8051F39x/37x SFR Definition 11.2. IDA0H: IDA0 Data Word MSB Bit 7 6 5 4 3 2 1 0 Name IDA0[9:2] Type R/W Reset 0 0 0 0 0 0 0 0 SFR Address=0x97; SFR Page=0 Bit Name Function 7:0 IDA0[9:2] IDA0 Data Word High-Order Bits. Upper 8 bits of the 10-bit IDA0 Data Word. SFR Definition 11.3. IDA0L: IDA0 Data Word LSB Bit 7 6 5 4 3 2 1 0 Name IDA0[1:0] Type R/W R R R R R R Reset 0 0 0 0 0 0 0 0 SFR Address=0x96; SFR Page=0 Bit Name Function 7:6 IDA0[1:0] IDA0 Data Word Low-Order Bits. Lower 2 bits of the 10-bit IDA0 Data Word. 5:0 Unused Unused. Read=000000b. Write=Don’t care. 70 Rev. 1.2

C8051F39x/37x SFR Definition 11.4. IDA1CN: IDA1 Control Bit 7 6 5 4 3 2 1 0 Name IDA1EN IDA1CM[2:0] IDA1RP IDA1OMD[1:0] Type R/W R/W R R/W R/W Reset 0 1 1 1 0 Varies 1 0 SFR Address=0xB9; SFR Page=F Bit Name Function 7 IDA1EN IDA1 Enable. 0: IDA1 Disabled. 1: IDA1 Enabled. 6:4 IDA1CM[2:0] IDA0 Update Source Select bits. 000: DAC output updates on Timer0 overflow. 001: DAC output updates on Timer5 overflow. 010: DAC output updates on Timer2 overflow. 011: DAC output updates on Timer3 overflow. 100: DAC output updates on rising edge of CNVSTR. 101: DAC output updates on falling edge of CNVSTR. 110: DAC output updates on any edge of CNVSTR. 111: DAC output updates on write to IDA1H. 3 Reserved Write=0b. 2 IDA1RP IDA1 Reset Persistence. 0: IDA1 is disabled by any reset source. 1: IDA1 will remain enabled through any reset source except a power-on-reset. This bit is reset to 0 by a power on reset, but is sticky through all other reset sources. When setting IDA1RP to 1, IDA1EN must be set to 1 also in the same move instruction. 1:0 IDA1OMD[1:0] IDA1 Output Mode Select bits. 00: 0.5mA full-scale output current. 01: 1.0mA full-scale output current. 1x: 2.0mA full-scale output current. Rev. 1.2 71

C8051F39x/37x SFR Definition 11.5. IDA1H: IDA1 Data Word MSB Bit 7 6 5 4 3 2 1 0 Name IDA1[9:2] Type R/W Reset 0 0 0 0 0 0 0 0 SFR Address=0x97; SFR Page=F Bit Name Function 7:0 IDA1[9:2] IDA1 Data Word High-Order Bits. Upper 8 bits of the 10-bit IDA1 Data Word. SFR Definition 11.6. IDA1L: IDA1 Data Word LSB Bit 7 6 5 4 3 2 1 0 Name IDA1[1:0] Type R/W R R R R R R Reset 0 0 0 0 0 0 0 0 SFR Address=0x96; SFR Page=F Bit Name Function 7:6 IDA1[1:0] IDA1 Data Word Low-Order Bits. Lower 2 bits of the 10-bit IDA1 Data Word. 5:0 Unused Unused. Read=000000b. Write=Don’t care. 72 Rev. 1.2

C8051F39x/37x 12. Voltage Reference Options The Voltage reference multiplexer for the ADC is configurable to use an externally connected voltage refer- ence, the on-chip reference voltage generator routed to the VREF pin, the unregulated power supply volt- age (V ), or the regulated 1.8V internal supply (see Figure12.1). The REFSL bit in the Reference DD Control register (REF0CN, SFR Definition 12.1) selects the reference source for the ADC. For an external source or the on-chip reference, REFSL should be set to 0 to select the VREF pin. To use V as the ref- DD erence source, REFSL should be set to 1. To override this selection and use the internal regulator as the reference source, the REGOVR bit can be set to 1. The BIASE bit enables the internal voltage bias generator, which is used by many of the analog peripherals on the device. This bias is automatically enabled when any peripheral which requires it is enabled, and it does not need to be enabled manually. The bias generator may be enabled manually by writing a 1 to the BIASE bit in register REF0CN. The electrical specifications for the voltage reference circuit are given in Table7.13. The C8051F390/2/4/6/8 and C8051F370/4 devices also include an on-chip voltage reference circuit which consists of a 1.2V, temperature stable bandgap voltage reference generator and a selectable-gain output buffer amplifier. The buffer is configured for 1x or 2x gain using the REFBGS bit in register REF0CN. On the 1x gain setting the output voltage is nominally 1.2V, and on the 2x gain setting the output voltage is nominally 2.4V. The on-chip voltage reference can be driven on the VREF pin by setting the REFBE bit in register REF0CN to a 1. The maximum load seen by the VREF pin must be less than 200µA to GND. Bypass capacitors of 0.1µF and 4.7µF are recommended from the VREF pin to GND, and a minimum of 0.1uF is required. If the on-chip reference is not used, the REFBE bit should be cleared to 0. Electrical specifications for the on-chip voltage reference are given in Table7.13. Important Note about the VREF Pin: When using either an external voltage reference or the on-chip ref- erence circuitry, the VREF pin should be configured as an analog pin and skipped by the Digital Crossbar. Refer to Section “27.Port Input/Output” on page173 for the location of the VREF pin, as well as details of how to configure the pin in analog mode and to be skipped by the crossbar. REF0CN REFBGS REGOVRREFSLTEMPEBIASEREFBE To ADC, IDAC, EN Internal Oscillators, Bias Generator Reference, IOSCEN TempSensor EN VDD External Temp Sensor To Analog Mux Voltage Reference R1 Circuit VREF EN 1x/2x 1.2V Reference REFBE REFBGS GND 0 0 + 4.7F 0.1F VREF VDD 1 (to ADC) Recommended Bypass Internal 1 Capacitors Regulator REGOVR Figure 12.1. Voltage Reference Functional Block Diagram Rev. 1.2 73

C8051F39x/37x SFR Definition 12.1. REF0CN: Reference Control Bit 7 6 5 4 3 2 1 0 Name REFBGS REGOVR REFSL TEMPE BIASE REFBE Type R/W R R R/W R/W R/W R/W R/W Reset 0 0 0 0 0 0 0 0 SFR Address=0xD1; SFR Page=All Pages Bit Name Function 7 REFBGS Reference Buffer Gain Select. This bit selects between 1x and 2x gain for the on-chip voltage ref- erence buffer. 0: 2x Gain 1: 1x Gain 6:5 Unused Read=00b; Write=Don’t care. 4 REGOVR Regulator Reference Override. This bit “overrides” the REFSL bit, and allows the internal regulator to be used as a reference source. 0: The voltage reference source is selected by the REFSL bit. 1: The internal regulator is used as the voltage reference. 3 REFSL Voltage Reference Select. This bit selects the ADCs voltage reference. 0: V pin used as voltage reference. REF 1: V used as voltage reference. DD 2 TEMPE Temperature Sensor Enable Bit. 0: Internal Temperature Sensor off. 1: Internal Temperature Sensor on. 1 BIASE Internal Analog Bias Generator Enable Bit. 0: Internal Bias Generator off. 1: Internal Bias Generator on. 0 REFBE On-chip Reference Buffer Enable Bit. 0: On-chip Reference Buffer off. 1: On-chip Reference Buffer on. Internal voltage reference driven on the V pin. REF 74 Rev. 1.2

C8051F39x/37x 13. Voltage Regulator C8051F39x/37x devices include an internal regulator that regulates the internal core supply from a V DD supply of 1.8to3.6V. The regulator has two power-saving modes built in to help reduce current consump- tion in low-power applications. These modes are accessed through the REG0CN register. 13.1. Power Modes Under default conditions, the internal regulator will remain on when the device enters STOP mode. This allows any enabled reset source to generate a reset for the device and bring the device out of STOP mode. For additional power savings, the STOPCF bit can be used to shut down the regulator and the internal power network of the device when the part enters STOP mode. When STOPCF is set to 1, the RST pin and a full power cycle of the device are the only methods of generating a reset. SFR Definition 13.1. REG0CN: Voltage Regulator Control Bit 7 6 5 4 3 2 1 0 Name STOPCF Type R/W R/W R/W Reset 0 0 0 0 0 0 0 0 SFR Address=0xC9; SFR Page=All Pages Bit Name Function 7:4 Reserved Must Write 0000b. 3 STOPCF Stop Mode Configuration. This bit configures the regulator’s behavior when the device enters STOP mode. 0: Regulator is still active in STOP mode. Any enabled reset source will reset the device. 1: Regulator is shut down in STOP mode. Only the RST pin or power cycle can reset the device. 2:0 Reserved Must Write 000b. Rev. 1.2 75

C8051F39x/37x 14. Comparator0 C8051F39x/37x devices include an on-chip programmable voltage comparator, Comparator0, shown in Figure14.1. The Comparator offers programmable response time and hysteresis, an analog input multiplexer, and two outputs that are optionally available at the Port pins: a synchronous “latched” output (CP0), or an asyn- chronous “raw” output (CP0A). The asynchronous CP0A signal is available even when the system clock is not active. This allows the Comparator to operate and generate an output with the device in STOP mode. When assigned to a Port pin, the Comparator output may be configured as open drain or push-pull (see Section “27.4.Port I/O Initialization” on page180). Comparator0 may also be used as a reset source (see Section “24.5.Comparator0 Reset” on page159), or as a trigger to kill a PCA output channel. The Comparator0 inputs are selected by the comparator input multiplexer, as detailed in Section “14.1.Comparator Multiplexer” on page80. CPT0CN CP0HYN0 CP0HYN1 CP0HYP0 CP0HYP1 CP0FIF CP0RIF CP0OUT CP0EN VDD CP0 + + Comparator CP0 Input Mux CP0 - DSETQ DSETQ - CLRQ CLRQ Crossbar (SYNCHRONIZER) CP0A GND CPT0MD Reset Decision Tree C C C C P P P P 0M 0M 0F 0R D0 D1 IE IE CP0RIF 0 CP0EN EA CP0 1 0 0 Interrupt 0 1 1 CP0FIF 1 Figure 14.1. Comparator0 Functional Block Diagram The Comparator output can be polled in software, used as an interrupt source, and/or routed to a Port pin. When routed to a Port pin, the Comparator output is available asynchronous or synchronous to the system clock; the asynchronous output is available even in STOP mode (with no system clock active). When dis- abled, the Comparator output (if assigned to a Port I/O pin via the Crossbar) defaults to the logic low state, and the power supply to the comparator is turned off. See Section “27.3.Priority Crossbar Decoder” on page178 for details on configuring Comparator outputs via the digital Crossbar. Comparator inputs can be externally driven from –0.25V to (V )+0.25V without damage or upset. The complete Comparator elec- DD trical specifications are given in Section “7.Electrical Characteristics” on page32. 76 Rev. 1.2

C8051F39x/37x The Comparator response time may be configured in software via the CPT0MD register (see SFR Defini- tion 14.2). Selecting a longer response time reduces the Comparator supply current. CP0+ VIN+ + CP0 OUT VIN- CP0- _ CIRCUIT CONFIGURATION Positive Hysteresis Voltage (Programmed with CP0HYP Bits) VIN- INPUTS Negative Hysteresis Voltage (Programmed by CP0HYN Bits) VIN+ VOH OUTPUT VOL Negative Hysteresis Maximum Disabled Negative Hysteresis Positive Hysteresis Maximum Disabled Positive Hysteresis Figure 14.2. Comparator Hysteresis Plot The Comparator hysteresis is software-programmable via its Comparator Control register CPT0CN. The user can program both the amount of hysteresis voltage (referred to the input voltage) and the positive and negative-going symmetry of this hysteresis around the threshold voltage. The Comparator hysteresis is programmed using Bits3–0 in the Comparator Control Register CPT0CN (shown in SFR Definition 14.1). The amount of negative hysteresis voltage is determined by the settings of the CP0HYN bits. As shown in Figure14.2, settings of 20, 10, or 5mV of negative hysteresis can be pro- grammed, or negative hysteresis can be disabled. In a similar way, the amount of positive hysteresis is determined by the setting the CP0HYP bits. Comparator interrupts can be generated on both rising-edge and falling-edge output transitions. (For Inter- rupt enable and priority control, see Section “20.1.MCU Interrupt Sources and Vectors” on page118). The CP0FIF flag is set to logic1 upon a Comparator falling-edge occurrence, and the CP0RIF flag is set to logic1 upon the Comparator rising-edge occurrence. Once set, these bits remain set until cleared by soft- ware. The Comparator rising-edge interrupt mask is enabled by setting CP0RIE to a logic1. The Compar- ator0 falling-edge interrupt mask is enabled by setting CP0FIE to a logic1. The output state of the Comparator can be obtained at any time by reading the CP0OUT bit. The Compar- ator is enabled by setting the CP0EN bit to logic1, and is disabled by clearing this bit to logic0. Note that false rising edges and falling edges can be detected when the comparator is first powered on or if changes are made to the hysteresis or response time control bits. Therefore, it is recommended that the rising-edge and falling-edge flags be explicitly cleared to logic0 a short time after the comparator is enabled or its mode bits have been changed. Rev. 1.2 77

C8051F39x/37x SFR Definition 14.1. CPT0CN: Comparator0 Control Bit 7 6 5 4 3 2 1 0 Name CP0EN CP0OUT CP0RIF CP0FIF CP0HYP[1:0] CP0HYN[1:0] Type R/W R R/W R/W R/W R/W Reset 0 0 0 0 0 0 0 0 SFR Address=0x9B; SFR Page=All Pages Bit Name Function 7 CP0EN Comparator0 Enable Bit. 0: Comparator0 Disabled. 1: Comparator0 Enabled. 6 CP0OUT Comparator0 Output State Flag. 0: Voltage on CP0+ < CP0–. 1: Voltage on CP0+ > CP0–. 5 CP0RIF Comparator0 Rising-Edge Flag. Must be cleared by software. 0: No Comparator0 Rising Edge has occurred since this flag was last cleared. 1: Comparator0 Rising Edge has occurred. 4 CP0FIF Comparator0 Falling-Edge Flag. Must be cleared by software. 0: No Comparator0 Falling-Edge has occurred since this flag was last cleared. 1: Comparator0 Falling-Edge has occurred. 3:2 CP0HYP[1:0] Comparator0 Positive Hysteresis Control Bits. 00: Positive Hysteresis Disabled. 01: Positive Hysteresis=5mV. 10: Positive Hysteresis=10mV. 11: Positive Hysteresis=20mV. 1:0 CP0HYN[1:0] Comparator0 Negative Hysteresis Control Bits. 00: Negative Hysteresis Disabled. 01: Negative Hysteresis=5mV. 10: Negative Hysteresis=10mV. 11: Negative Hysteresis=20mV. 78 Rev. 1.2

C8051F39x/37x SFR Definition 14.2. CPT0MD: Comparator0 Mode Selection Bit 7 6 5 4 3 2 1 0 Name CP0RIE CP0FIE CP0MD[1:0] Type R R R/W R/W R R R/W Reset 0 0 0 0 0 0 1 0 SFR Address=0x9D; SFR Page=All Pages Bit Name Function 7:6 Unused Unused. Read=00b, Write=Don’t Care. 5 CP0RIE Comparator0 Rising-Edge Interrupt Enable. 0: Comparator0 Rising-edge interrupt disabled. 1: Comparator0 Rising-edge interrupt enabled. 4 CP0FIE Comparator0 Falling-Edge Interrupt Enable. 0: Comparator0 Falling-edge interrupt disabled. 1: Comparator0 Falling-edge interrupt enabled. 3:2 Unused Unused. Read=00b, Write=don’t care. 1:0 CP0MD[1:0] Comparator0 Mode Select. These bits affect the response time and power consumption for Comparator0. 00: Mode 0 (Fastest Response Time, Highest Power Con- sumption) 01: Mode 1 10: Mode 2 11: Mode 3 (Slowest Response Time, Lowest Power Con- sumption) Rev. 1.2 79

C8051F39x/37x 14.1. Comparator Multiplexer C8051F39x/37x devices include an analog input multiplexer to connect Port I/O pins to the comparator inputs. The Comparator0 inputs are selected in the CPT0MX register (SFR Definition 14.3). The CMX0P1– CMX0P0 bits select the Comparator0 positive input; the CMX0N1–CMX0N0 bits select the Comparator0 negative input. Important Note About Comparator Inputs: The Port pins selected as comparator inputs should be configured as analog inputs in their associated Port configuration register, and configured to be skipped by the Crossbar (for details on Port configuration, see Section “27.6.Special Function Registers for Accessing and Configuring Port I/O” on page185). CPT0MX C C C C C C C C M M M M M M M M X X X X X X X X 0 0 0 0 0 0 0 0 P P P P N N N N 0 1 2 3 0 1 2 3 P0.0 P0.2 P0.4 P0.6 P1.0 P1.2 P1.4 VDD P1.6 P2.0* CP0 + P2.2* + CP0 - P0.1 - P0.3 P0.5 P0.7 GND P1.1 P1.3 P1.5 P1.7 *P2.0-P2.3 Only available as P2.1* inputs on QFN24 Packaging P2.3* Figure 14.3. Comparator Input Multiplexer Block Diagram 80 Rev. 1.2

C8051F39x/37x SFR Definition 14.3. CPT0MX: Comparator0 MUX Selection Bit 7 6 5 4 3 2 1 0 Name CMX0N[3:0] CMX0P[3:0] Type R/W R/W Reset 1 1 1 1 1 1 1 1 SFR Address=0x9F; SFR Page=All Pages Bit Name Function 7:4 CMX0N[3:0] Comparator0 Negative Input MUX Selection. 0000: P0.1 0001: P0.3 0010: P0.5 0011: P0.7 0100: P1.1 0101: P1.3 0110: P1.5 0111: P1.7 1000: P2.1 (C8051F390/1/4/5 and C8051F37x Only) 1001: P2.3 (C8051F390/1/4/5 and C8051F37x Only) 1010-1111: None 3:0 CMX0P[3:0] Comparator0 Positive Input MUX Selection. 0000: P0.0 0001: P0.2 0010: P0.4 0011: P0.6 0100: P1.0 0101: P1.2 0110: P1.4 0111: P1.6 1000: P2.0 (C8051F390/1/4/5 and C8051F37x Only) 1001: P2.2 (C8051F390/1/4/5 and C8051F37x Only) 1010-1111: None Rev. 1.2 81

C8051F39x/37x 15. CIP-51 Microcontroller The MCU system controller core is the CIP-51 microcontroller. The CIP-51 is fully compatible with the MCS-51™ instruction set; standard 803x/805x assemblers and compilers can be used to develop soft- ware. The MCU family has a superset of all the peripherals included with a standard 8051. The CIP-51 also includes on-chip debug hardware (see description in Section 33), and interfaces directly with the ana- log and digital subsystems providing a complete data acquisition or control-system solution in a single inte- grated circuit. The CIP-51 Microcontroller core implements the standard 8051 organization and peripherals as well as additional custom peripherals and functions to extend its capability (see Figure15.1 for a block diagram). The CIP-51 includes the following features:  Fully Compatible with MCS-51 Instruction Set  Reset Input  50MIPS Peak Throughput with 49MHz Clock  Power Management Modes  0 to 49MHz Clock Frequency  On-chip Debug Logic  Extended Interrupt Handler  Program and Data Memory Security Performance The CIP-51 employs a pipelined architecture that greatly increases its instruction throughput over the stan- dard 8051 architecture. In a standard 8051, all instructions except for MUL and DIV take 12 or 24 system clock cycles to execute, and usually have a maximum system clock of 12MHz. By contrast, the CIP-51 core executes 70% of its instructions in one or two system clock cycles, with no instructions taking more than eight system clock cycles. DATA BUS D8 D8 D8 ACCUMULATOR D8 D8 B REGISTER STACK POINTER S BU TMP1 TMP2 A T A SRAM D PSW ADDRESS SRAM ALU REGISTER D8 D8 D8 D8 DATA BUS SFR_ADDRESS BUFFER D8 SFR SFR_CONTROL DATA POINTER D8 D8 INTEBRUFSACE SFR_WRITE_DATA SFR_READ_DATA PC INCREMENTER PROGRAM COUNTER (PC) US D8 MEM_ADDRESS B PRGM. ADDRESS REG. ATA A16 INMTEEMROFARCYE MEMM_EWMR_CITOEN_TDRAOTAL D MEM_READ_DATA PIPELINE D8 RESET CONTROL LOGIC SYSTEM_IRQs CLOCK INTERRUPT STOP D8 INTERFACE EMULATION_IRQ POWER CONTROL IDLE REGISTER D8 Figure 15.1. CIP-51 Block Diagram 82 Rev. 1.2

C8051F39x/37x With the CIP-51's maximum system clock at 48MHz, it has a peak throughput of 48MIPS. The CIP-51 has a total of 109 instructions. The table below shows the total number of instructions that require each execu- tion time. Clocks to Execute 1 2 2/4 3 3/5 4 5 4/6 6 8 Number of Instructions 26 50 5 10 7 5 2 1 2 1 Programming and Debugging Support In-system programming of the EPROM program memory and communication with on-chip debug support logic is accomplished via the Silicon Labs 2-Wire Development Interface (C2). The on-chip debug support logic facilitates full speed in-circuit debugging, allowing the setting of hardware breakpoints, starting, stopping and single stepping through program execution (including interrupt service routines), examination of the program's call stack, and reading/writing the contents of registers and mem- ory. This method of on-chip debugging is completely non-intrusive, requiring no RAM, Stack, timers, or other on-chip resources. C2 details can be found in Section “33.C2 Interface” on page297. The CIP-51 is supported by development tools from Silicon Labs and third party vendors. Silicon Labs pro- vides an integrated development environment (IDE) including editor, debugger and programmer. The IDE's debugger and programmer interface to the CIP-51 via the C2 interface to provide fast and efficient in-sys- tem device programming and debugging. Third party macro assemblers and C compilers are also avail- able. 15.1. Instruction Set The instruction set of the CIP-51 System Controller is fully compatible with the standard MCS-51™ instruc- tion set. Standard 8051 development tools can be used to develop software for the CIP-51. All CIP-51 instructions are the binary and functional equivalent of their MCS-51™ counterparts, including opcodes, addressing modes and effect on PSW flags. However, instruction timing is different than that of the stan- dard 8051. 15.1.1. Instruction and CPU Timing In many 8051 implementations, a distinction is made between machine cycles and clock cycles, with machine cycles varying from 2 to 12 clock cycles in length. However, the CIP-51 implementation is based solely on clock cycle timing. All instruction timings are specified in terms of clock cycles. Due to the pipelined architecture of the CIP-51, most instructions execute in the same number of clock cycles as there are program bytes in the instruction. Conditional branch instructions take one less clock cycle to complete when the branch is not taken as opposed to when the branch is taken. Table15.1 is the CIP-51 Instruction Set Summary, which includes the mnemonic, number of bytes, and number of clock cycles for each instruction. Rev. 1.2 83

C8051F39x/37x Table 15.1. CIP-51 Instruction Set Summary Mnemonic Description Bytes Clock Cycles Arithmetic Operations ADD A, Rn Add register to A 1 1 ADD A, direct Add direct byte to A 2 2 ADD A, @Ri Add indirect RAM to A 1 2 ADD A, #data Add immediate to A 2 2 ADDC A, Rn Add register to A with carry 1 1 ADDC A, direct Add direct byte to A with carry 2 2 ADDC A, @Ri Add indirect RAM to A with carry 1 2 ADDC A, #data Add immediate to A with carry 2 2 SUBB A, Rn Subtract register from A with borrow 1 1 SUBB A, direct Subtract direct byte from A with borrow 2 2 SUBB A, @Ri Subtract indirect RAM from A with borrow 1 2 SUBB A, #data Subtract immediate from A with borrow 2 2 INC A Increment A 1 1 INC Rn Increment register 1 1 INC direct Increment direct byte 2 2 INC @Ri Increment indirect RAM 1 2 DEC A Decrement A 1 1 DEC Rn Decrement register 1 1 DEC direct Decrement direct byte 2 2 DEC @Ri Decrement indirect RAM 1 2 INC DPTR Increment Data Pointer 1 1 MUL AB Multiply A and B 1 4 DIV AB Divide A by B 1 8 DA A Decimal adjust A 1 1 Logical Operations ANL A, Rn AND Register to A 1 1 ANL A, direct AND direct byte to A 2 2 ANL A, @Ri AND indirect RAM to A 1 2 ANL A, #data AND immediate to A 2 2 ANL direct, A AND A to direct byte 2 2 ANL direct, #data AND immediate to direct byte 3 3 ORL A, Rn OR Register to A 1 1 ORL A, direct OR direct byte to A 2 2 ORL A, @Ri OR indirect RAM to A 1 2 ORL A, #data OR immediate to A 2 2 ORL direct, A OR A to direct byte 2 2 ORL direct, #data OR immediate to direct byte 3 3 XRL A, Rn Exclusive-OR Register to A 1 1 XRL A, direct Exclusive-OR direct byte to A 2 2 XRL A, @Ri Exclusive-OR indirect RAM to A 1 2 XRL A, #data Exclusive-OR immediate to A 2 2 XRL direct, A Exclusive-OR A to direct byte 2 2 84 Rev. 1.2

C8051F39x/37x Table 15.1. CIP-51 Instruction Set Summary (Continued) Mnemonic Description Bytes Clock Cycles XRL direct, #data Exclusive-OR immediate to direct byte 3 3 CLR A Clear A 1 1 CPL A Complement A 1 1 RL A Rotate A left 1 1 RLC A Rotate A left through Carry 1 1 RR A Rotate A right 1 1 RRC A Rotate A right through Carry 1 1 SWAP A Swap nibbles of A 1 1 Data Transfer MOV A, Rn Move Register to A 1 1 MOV A, direct Move direct byte to A 2 2 MOV A, @Ri Move indirect RAM to A 1 2 MOV A, #data Move immediate to A 2 2 MOV Rn, A Move A to Register 1 1 MOV Rn, direct Move direct byte to Register 2 2 MOV Rn, #data Move immediate to Register 2 2 MOV direct, A Move A to direct byte 2 2 MOV direct, Rn Move Register to direct byte 2 2 MOV direct, direct Move direct byte to direct byte 3 3 MOV direct, @Ri Move indirect RAM to direct byte 2 2 MOV direct, #data Move immediate to direct byte 3 3 MOV @Ri, A Move A to indirect RAM 1 2 MOV @Ri, direct Move direct byte to indirect RAM 2 2 MOV @Ri, #data Move immediate to indirect RAM 2 2 MOV DPTR, #data16 Load DPTR with 16-bit constant 3 3 MOVC A, @A+DPTR Move code byte relative DPTR to A 1 3 MOVC A, @A+PC Move code byte relative PC to A 1 3 MOVX A, @Ri Move external data (8-bit address) to A 1 3 MOVX @Ri, A Move A to external data (8-bit address) 1 3 MOVX A, @DPTR Move external data (16-bit address) to A 1 3 MOVX @DPTR, A Move A to external data (16-bit address) 1 3 PUSH direct Push direct byte onto stack 2 2 POP direct Pop direct byte from stack 2 2 XCH A, Rn Exchange Register with A 1 1 XCH A, direct Exchange direct byte with A 2 2 XCH A, @Ri Exchange indirect RAM with A 1 2 XCHD A, @Ri Exchange low nibble of indirect RAM with A 1 2 Boolean Manipulation CLR C Clear Carry 1 1 CLR bit Clear direct bit 2 2 SETB C Set Carry 1 1 SETB bit Set direct bit 2 2 CPL C Complement Carry 1 1 CPL bit Complement direct bit 2 2 Rev. 1.2 85

C8051F39x/37x Table 15.1. CIP-51 Instruction Set Summary (Continued) Mnemonic Description Bytes Clock Cycles ANL C, bit AND direct bit to Carry 2 2 ANL C, /bit AND complement of direct bit to Carry 2 2 ORL C, bit OR direct bit to carry 2 2 ORL C, /bit OR complement of direct bit to Carry 2 2 MOV C, bit Move direct bit to Carry 2 2 MOV bit, C Move Carry to direct bit 2 2 JC rel Jump if Carry is set 2 2/4 JNC rel Jump if Carry is not set 2 2/4 JB bit, rel Jump if direct bit is set 3 3/5 JNB bit, rel Jump if direct bit is not set 3 3/5 JBC bit, rel Jump if direct bit is set and clear bit 3 3/5 Program Branching ACALL addr11 Absolute subroutine call 2 4* LCALL addr16 Long subroutine call 3 5* RET Return from subroutine 1 6* RETI Return from interrupt 1 6* AJMP addr11 Absolute jump 2 4* LJMP addr16 Long jump 3 5* SJMP rel Short jump (relative address) 2 4* JMP @A+DPTR Jump indirect relative to DPTR 1 4* JZ rel Jump if A equals zero 2 2/4* JNZ rel Jump if A does not equal zero 2 2/4* CJNE A, direct, rel Compare direct byte to A and jump if not equal 3 4/6* CJNE A, #data, rel Compare immediate to A and jump if not equal 3 3/5* CJNE Rn, #data, rel Compare immediate to Register and jump if not 3 3/5* equal CJNE @Ri, #data, rel Compare immediate to indirect and jump if not 3 4/6* equal DJNZ Rn, rel Decrement Register and jump if not zero 2 2/4* DJNZ direct, rel Decrement direct byte and jump if not zero 3 3/5* NOP No operation 1 1 * Clock cycles for branch instructions with prefetch enabled, Align=0, FLRT=0 86 Rev. 1.2

C8051F39x/37x Notes on Registers, Operands and Addressing Modes: Rn - Register R0–R7 of the currently selected register bank. @Ri - Data RAM location addressed indirectly through R0 or R1. rel - 8-bit, signed (two’s complement) offset relative to the first byte of the following instruction. Used by SJMP and all conditional jumps. direct - 8-bit internal data location’s address. This could be a direct-access Data RAM location (0x00– 0x7F) or an SFR (0x80–0xFF). #data - 8-bit constant #data16 - 16-bit constant bit - Direct-accessed bit in Data RAM or SFR addr11 - 11-bit destination address used by ACALL and AJMP. The destination must be within the same 2kB page of program memory as the first byte of the following instruction. addr16 - 16-bit destination address used by LCALL and LJMP. The destination may be anywhere within the 8kB program memory space. There is one unused opcode (0xA5) that performs the same function as NOP. All mnemonics copyrighted © Intel Corporation 1980. 15.2. CIP-51 Register Descriptions Following are descriptions of SFRs related to the operation of the CIP-51 System Controller. Reserved bits should always be written to the value indicated in the SFR description. Future product versions may use these bits to implement new features in which case the reset value of the bit will be the indicated value, selecting the feature's default state. Detailed descriptions of the remaining SFRs are included in the sec- tions of the datasheet associated with their corresponding system function. Rev. 1.2 87

C8051F39x/37x SFR Definition 15.1. DPL: Data Pointer Low Byte Bit 7 6 5 4 3 2 1 0 Name DPL[7:0] Type R/W Reset 0 0 0 0 0 0 0 0 SFR Address=0x82; SFR Page=All Pages Bit Name Function 7:0 DPL[7:0] Data Pointer Low. The DPL register is the low byte of the 16-bit DPTR. SFR Definition 15.2. DPH: Data Pointer High Byte Bit 7 6 5 4 3 2 1 0 Name DPH[7:0] Type R/W Reset 0 0 0 0 0 0 0 0 SFR Address=0x83; SFR Page=All Pages Bit Name Function 7:0 DPH[7:0] Data Pointer High. The DPH register is the high byte of the 16-bit DPTR. 88 Rev. 1.2

C8051F39x/37x SFR Definition 15.3. SP: Stack Pointer Bit 7 6 5 4 3 2 1 0 Name SP[7:0] Type R/W Reset 0 0 0 0 0 1 1 1 SFR Address=0x81; SFR Page=All Pages Bit Name Function 7:0 SP[7:0] Stack Pointer. The Stack Pointer holds the location of the top of the stack. The stack pointer is incremented before every PUSH operation. The SP register defaults to 0x07 after reset. SFR Definition 15.4. ACC: Accumulator Bit 7 6 5 4 3 2 1 0 Name ACC[7:0] Type R/W Reset 0 0 0 0 0 0 0 0 SFR Address=0xE0; SFR Page=All Pages; Bit-Addressable Bit Name Function 7:0 ACC[7:0] Accumulator. This register is the accumulator for arithmetic operations. Rev. 1.2 89

C8051F39x/37x SFR Definition 15.5. B: B Register Bit 7 6 5 4 3 2 1 0 Name B[7:0] Type R/W Reset 0 0 0 0 0 0 0 0 SFR Address=0xF0; SFR Page=All Pages; Bit-Addressable Bit Name Function 7:0 B[7:0] B Register. This register serves as a second accumulator for certain arith- metic operations. 90 Rev. 1.2

C8051F39x/37x SFR Definition 15.6. PSW: Program Status Word Bit 7 6 5 4 3 2 1 0 Name CY AC F0 RS[1:0] OV F1 PARITY Type R/W R/W R/W R/W R/W R/W R Reset 0 0 0 0 0 0 0 0 SFR Address=0xD0; SFR Page=All Pages; Bit-Addressable Bit Name Function 7 CY Carry Flag. This bit is set when the last arithmetic operation resulted in a carry (addition) or a borrow (subtraction). It is cleared to logic 0 by all other arithmetic operations. 6 AC Auxiliary Carry Flag. This bit is set when the last arithmetic operation resulted in a carry into (addition) or a borrow from (subtraction) the high order nibble. It is cleared to logic 0 by all other arithmetic operations. 5 F0 User Flag 0. This is a bit-addressable, general purpose flag for use under soft- ware control. 4:3 RS[1:0] Register Bank Select. These bits select which register bank is used during register accesses. 00: Bank 0, Addresses 0x00-0x07 01: Bank 1, Addresses 0x08-0x0F 10: Bank 2, Addresses 0x10-0x17 11: Bank 3, Addresses 0x18-0x1F 2 OV Overflow Flag. This bit is set to 1 under the following circumstances: An ADD, ADDC, or SUBB instruction causes a sign-change overflow. A MUL instruction results in an overflow (result is greater than 255). A DIV instruction causes a divide-by-zero condition. The OV bit is cleared to 0 by the ADD, ADDC, SUBB, MUL, and DIV instructions in all other cases. 1 F1 User Flag 1. This is a bit-addressable, general purpose flag for use under soft- ware control. 0 PARITY Parity Flag. This bit is set to logic 1 if the sum of the eight bits in the accumula- tor is odd and cleared if the sum is even. Rev. 1.2 91

C8051F39x/37x 16. Prefetch Engine The C8051F39x/37x family of devices incorporate a 2-byte prefetch engine. Because the access time of the Flash memory is 40ns, and the minimum instruction time is roughly 20ns, the prefetch engine is nec- essary for code execution above 25 MHz. When operating the device with SYSCLK greater than 25 MHz, the prefetch engine must be enabled by setting the PFEN bit in the PFE0CN register and the FLRT bit in the FLSCL register to 1. Instructions are read from Flash memory two bytes at a time by the prefetch engine and given to the CIP- 51 processor core to execute. When running linear code (code without any jumps or branches), the prefetch engine allows instructions to be executed at full speed. When a code branch occurs, the proces- sor may be stalled for up to two clock cycles while the next set of code bytes is retrieved from Flash mem- ory. Note: The prefetch engine should be disabled when the device is in suspend mode to save power. SFR Definition 16.1. PFE0CN: Prefetch Engine Control Bit 7 6 5 4 3 2 1 0 Name PFEN Type R R R/W R R R R R Reset 0 0 0 0 0 0 0 0 SFR Address=0xB5; SFR Page=All Pages Bit Name Function 7:6 Unused Unused. Read=00b, Write=don’t care. 5 PFEN Prefetch Enable. This bit enables the prefetch engine. 0: Prefetch engine is disabled. 1: Prefetch engine is enabled. 4:0 Unused Unused. Read=00000b. Write=don’t care. 92 Rev. 1.2

C8051F39x/37x 17. Memory Organization The memory organization of the CIP-51 System Controller is similar to that of a standard 8051. There are two separate memory spaces: program memory and data memory. Program and data memory share the same address space but are accessed via different instruction types. The memory organization of the C8051F39x/37x device family is shown in Figure17.1. Not shown in Figure17.1 is 512 bytes of byte- addressable EEPROM available on C8051F37x, accessible by SMBUS/I2C (see Section 22). PROGRAM/DATA MEMORY (FLASH) DATA MEMORY (RAM) C8051F390/1/2/3, C8051F370/1 INTERNAL DATA ADDRESS SPACE 0x4000 0xFF Upper 128 RAM Special Function (Indirect Addressing Register's Only) (Direct Addressing Only) 0x80 0 16 kB FLASH 0x7F F (Direct and Indirect (In-System Addressing) Programmable in 512 Lower 128 RAM 0x30 Byte Sectors) (Direct and Indirect 0x2F Bit Addressable Addressing) 0x20 0x1F General Purpose 0x0000 0x00 Registers C8051F394/5/6/7, C8051F374/5 EXTERNAL DATA ADDRESS SPACE 0x2000 0xFFFF Same 1024 bytes as from 0x0000 to 0x03FF, wrapped 8 kB FLASH on 1024-byte boundaries 0x0400 (In-System 0x03FF Programmable in 512 Always Reads 0x00 Byte Sectors) 0x0300 0x02FF XRAM - 768 Bytes (accessable using MOVX 0x0000 0x0000 instruction) C8051F398/9 0x1000 4 kB FLASH (In-System Programmable in 512 Byte Sectors) 0x0000 Figure 17.1. C8051F39x/37x Memory Map Rev. 1.2 93

C8051F39x/37x 17.1. Program Memory The CIP-51 core has a 64kB program memory space. The C8051F39x/37x implements 16kB of this pro- gram memory space as in-system, re-programmable Flash memory, organized in a contiguous block from addresses 0x0000 to 0x3FFF. The address 0x3FFF serves as the security lock byte for the device, and addresses above 0x3FFF are reserved. C8051F390/1/2/3 C8051F394/5/6/7 C8051F398/9 C8051F370/1 C8051F374/5 Lock Byte 0x3FFF 0x3FFE Lock Byte Page n 0x3E00 d i e z Lock By te 0x1FFF nis ae gg Lock Byte Page 00xx11FEF0E0 mory orbyte pa Flash Memory Space Lock By te 0x0FFF me12- 0x0FFE H 5 Lock Byte Page S Flash Memory Space A 0x0E00 L F Flash Memory Space 0x0000 0x0000 0x0000 Figure 17.2. Flash Program Memory Map 17.1.1. MOVX Instruction and Program Memory The MOVX instruction in an 8051 device is typically used to access external data memory. On the C8051F39x/37x devices, the MOVX instruction is normally used to read and write on-chip XRAM, but can be re-configured to write and erase on-chip Flash memory space. MOVC instructions are always used to read Flash memory, while MOVX write instructions are used to erase and write Flash. This Flash access feature provides a mechanism for the C8051F39x/37x to update program code and use the program mem- ory space for non-volatile data storage. Refer to Section “21.Flash Memory” on page131 for further details. 17.2. Data Memory The C8051F39x/37x device family includes 1024 bytes of RAM data memory. 256 bytes of this memory is mapped into the internal RAM space of the 8051. 768 bytes of this memory is on-chip “external” memory. The data memory map is shown in Figure17.1 for reference. 17.2.1. Internal RAM There are 256 bytes of internal RAM mapped into the data memory space from 0x00 through 0xFF. The lower 128bytes of data memory are used for general purpose registers and scratch pad memory. Either direct or indirect addressing may be used to access the lower 128bytes of data memory. Locations 0x00 through 0x1F are addressable as four banks of general purpose registers, each bank consisting of eight byte-wide registers. The next 16bytes, locations 0x20 through 0x2F, may either be addressed as bytes or as 128bit locations accessible with the direct addressing mode. The upper 128bytes of data memory are accessible only by indirect addressing. This region occupies the same address space as the Special Function Registers (SFR) but is physically separate from the SFR space. The addressing mode used by an instruction when accessing locations above 0x7F determines whether the CPU accesses the upper 128bytes of data memory space or the SFRs. Instructions that use direct addressing will access the SFR space. Instructions using indirect addressing above 0x7F access the 94 Rev. 1.2

C8051F39x/37x upper 128bytes of data memory. Figure17.1 illustrates the data memory organization of the C8051F39x/ 37x. 17.2.1.1. General Purpose Registers The lower 32 bytes of data memory, locations 0x00 through 0x1F, may be addressed as four banks of gen- eral-purpose registers. Each bank consists of eight byte-wide registers designated R0 through R7. Only one of these banks may be enabled at a time. Two bits in the program status word, RS0 (PSW.3) and RS1 (PSW.4), select the active register bank (see description of the PSW in SFR Definition 15.6). This allows fast context switching when entering subroutines and interrupt service routines. Indirect addressing modes use registers R0 and R1 as index registers. 17.2.1.2. Bit Addressable Locations In addition to direct access to data memory organized as bytes, the sixteen data memory locations at 0x20 through 0x2F are also accessible as 128individually addressable bits. Each bit has a bit address from 0x00 to 0x7F. Bit0 of the byte at 0x20 has bit address 0x00 while bit7 of the byte at 0x20 has bit address 0x07. Bit 7 of the byte at 0x2F has bit address 0x7F. A bit access is distinguished from a full byte access by the type of instruction used (bit source or destination operands as opposed to a byte source or destina- tion). The MCS-51™ assembly language allows an alternate notation for bit addressing of the form XX.B where XX is the byte address and B is the bit position within the byte. For example, the instruction: MOV C, 22.3h moves the Boolean value at 0x13 (bit 3 of the byte at location 0x22) into the Carry flag. 17.2.1.3. Stack A programmer's stack can be located anywhere in the 256-byte data memory. The stack area is desig- nated using the Stack Pointer (SP) SFR. The SP will point to the last location used. The next value pushed on the stack is placed at SP+1 and then SP is incremented. A reset initializes the stack pointer to location 0x07. Therefore, the first value pushed on the stack is placed at location 0x08, which is also the first regis- ter (R0) of register bank 1. Thus, if more than one register bank is to be used, the SP should be initialized to a location in the data memory not being used for data storage. The stack depth can extend up to 256bytes. 17.2.2. External RAM There are 768bytes of on-chip RAM mapped into the external data memory space. All of these address locations may be accessed using the external move instruction (MOVX) and the data pointer (DPTR), or using MOVX indirect addressing mode. If the MOVX instruction is used with an 8-bit address operand (such as @R1), then the high byte of the 16-bit address is provided by the External Memory Interface Con- trol Register (EMI0CN as shown in SFR Definition 17.1). Note: the MOVX instruction is also used for writes to the Flash memory. See Section “21.Flash Memory” on page131 for details. The MOVX instruction accesses XRAM by default. Memory locations between address 0x0300 and 0x03FF will all read back 0x00. For a 16-bit MOVX operation (@DPTR), the upper 6 bits of the 16-bit external data memory address word are "don't cares". As a result, addresses 0x0000 through 0x03FF are mapped modulo style over the entire 64k external data memory address range. For example, the XRAM byte at address 0x0000 is shadowed at addresses 0x0400, 0x0800, 0x0C00, 0x1000, etc. Rev. 1.2 95

C8051F39x/37x SFR Definition 17.1. EMI0CN: External Memory Interface Control Bit 7 6 5 4 3 2 1 0 Name PGSEL Type R R R R R R R/W Reset 0 0 0 0 0 0 0 0 SFR Address=0xAA; SFR Page=All Pages Bit Name Function 7:2 Unused Read=000000b; Write=Don’t Care 1:0 PGSEL XRAM Page Select. The PGSEL field provides the high byte of the 16-bit external data memory address when using an 8-bit MOVX command, effectively selecting a 256-byte page of RAM. Since the upper (unused) bits of the register are always zero, the PGSEL deter- mines which page of XRAM is accessed. For Example: If PGSEL=0x01, addresses 0x0100 through 0x01FF will be accessed. 96 Rev. 1.2

C8051F39x/37x 18. Device ID Registers The C8051F39x/37x has SFRs that identify the device family and derivative. These SFRs can be read by firmware at runtime to determine the capabilities of the MCU that is executing code. This allows the same firmware image to run on MCUs with different memory sizes and peripherals, and dynamically changing functionality to suit the capabilities of that MCU. In order for firmware to identify the MCU, it must read two SFRs. DERIVID describes the specific derivative within that device family, and REVID describes the hardware revision of the MCU. The C8051F39x/37x devices also include four SFRs, SN0 through SN3, that are pre-programmed during production with a unique, 32-bit serial number. The serial number provides a unique identification number for each device and can be read from the application firmware. If the serial number is not used in the appli- cation, these four registers can be used as general purpose SFRs. SFR Definition 18.1. DERIVID: Device Derivative ID Bit 7 6 5 4 3 2 1 0 Name DERIVID Type R Reset Varies Varies Varies Varies Varies Varies Varies Varies SFR Address=0xAB; SFR Page=0 Bit Name Function 7:0 DERIVID Derivative ID. This read-only register returns the 8-bit derivative ID, which can be used by firmware to identify which device in the product family is being used. 0xD0: C8051F390 0xD1: C8051F391 0xD2: C8051F392 0xD3: C8051F393 0xD4: C8051F394 0xD5: C8051F395 0xD6: C8051F396 0xD7: C8051F397 0xD8: C8051F398 0xD9: C8051F399 0xE0: C8051F370 0xE1: C8051F371 0xE4: C8051F374 0xE5: C8051F375 Rev. 1.2 97

C8051F39x/37x SFR Definition 18.2. REVISION: Device Revision ID Bit 7 6 5 4 3 2 1 0 Name REVISION Type R Reset Varies Varies Varies Varies Varies Varies Varies Varies SFR Address=0xAC; SFR Page=0 Bit Name Function 7:0 REVISION Device Revision. This read-only register returns the 8-bit revision ID. For example: 0x00=Revision A. SFR Definition 18.3. SN3: Serial Number Byte 3 Bit 7 6 5 4 3 2 1 0 Name SN3 Type R Reset Varies Varies Varies Varies Varies Varies Varies Varies SFR Address=0xAE; SFR Page=F Bit Name Function 7:0 SN3 Serial Number Byte 3. This read-only register returns the MSB (byte 3) of the serial num- ber. 98 Rev. 1.2

C8051F39x/37x SFR Definition 18.4. SN2: Serial Number Byte 2 Bit 7 6 5 4 3 2 1 0 Name SN2 Type R Reset Varies Varies Varies Varies Varies Varies Varies Varies SFR Address=0xAD; SFR Page=F Bit Name Function 7:0 SN2 Serial Number Byte 2. This read-only register returns the byte 2 of the serial number. SFR Definition 18.5. SN1: Serial Number Byte 1 Bit 7 6 5 4 3 2 1 0 Name SN1 Type R Reset Varies Varies Varies Varies Varies Varies Varies Varies SFR Address=0xAC; SFR Page=F Bit Name Function 7:0 SN1 Serial Number Byte 1. This read-only register returns byte 1 of the serial number. Rev. 1.2 99

C8051F39x/37x SFR Definition 18.6. SN0: Serial Number Byte 0 Bit 7 6 5 4 3 2 1 0 Name SN0 Type R Reset Varies Varies Varies Varies Varies Varies Varies Varies SFR Address=0xAB; SFR Page=F Bit Name Function 7:0 SN0 Serial Number Byte 0. This read-only register returns the LSB (byte 0) of the serial num- ber. 100 Rev. 1.2

C8051F39x/37x 19. Special Function Registers The direct-access data memory locations from 0x80 to 0xFF constitute the special function registers (SFRs). The SFRs provide control and data exchange with the C8051F39x/37x's resources and peripher- als. The CIP-51 controller core duplicates the SFRs found in a typical 8051 implementation as well as implementing additional SFRs used to configure and access the sub-systems unique to the C8051F39x/ 37x. This allows the addition of new functionality while retaining compatibility with the MCS-51™ instruc- tion set. Table19.2 lists the SFRs implemented in the C8051F39x/37x device family. The SFR registers are accessed anytime the direct addressing mode is used to access memory locations from 0x80 to 0xFF. SFRs with addresses ending in 0x0 or 0x8 (e.g. P0, TCON, SCON0, IE, etc.) are bit- addressable as well as byte-addressable. All other SFRs are byte-addressable only. Unoccupied addresses in the SFR space are reserved for future use. Accessing these areas will have an indeterminate effect and should be avoided. Refer to the corresponding pages of the data sheet, as indicated in Table19.3, for a detailed description of each register. 19.1. SFR Paging The CIP-51 features SFR paging, allowing the device to map many SFRs into the 0x80 to 0xFF memory address space. The SFR memory space has 256 pages. In this way, each memory location from 0x80 to 0xFF can access up to 256 SFRs. The C8051F39x/37x devices utilize two SFR pages: 0x0, and 0xF. Most SFRs are available on both pages. SFR pages are selected using the Special Function Register Page Selection register, SFRPAGE. The procedure for reading and writing an SFR is as follows: 1. Select the appropriate SFR page number using the SFRPAGE register. 2. Use direct accessing mode to read or write the special function register (MOV instruction). 19.2. Interrupts and Automatic SFR Paging When an interrupt occurs, the current SFRPAGE is pushed onto the SFR page stack. Upon execution of the RETI instruction, the SFR page is automatically restored to the SFR page in use prior to the interrupt. This is accomplished via a five-byte SFR page stack, depicted in Figure19.1. Firmware can read any ele- ment of the SFR page stack by setting the SFR Page Stack Index (SFRPGIDX) in the SFR Page Control Register (SFRPGCN) and reading the SFRSTACK register: Table 19.1. SFR Page Stack SFRPGIDX Value SFRSTACK Contains 000b Value of the first/top* byte of the stack 001b Value of the second byte of the stack 011b Value of the third byte of the stack 010b Value of the forth byte of the stack 100b Value of the fifth/bottom byte of the stack *Note: The first/top byte of the stack can also be directly accessed by reading SFRPAGE. Rev. 1.2 101

C8051F39x/37x SFRPGCN 210 XXX N DDD E SFRPGEN GIGIGI G P PPP R RRR F FFF S SSS Interrupt Logic SFRPAGE 000 001 SFR Page 010 SFRSTACK Stack 011 100 Figure 19.1. SFR Page Stack Upon an interrupt, hardware performs the five following operations: 1. The value (if any) in the SFRPGIDX = 011b location is pushed to the SFRPAGE = 100b location. 2. The value (if any) in the SFRPGIDX = 010b location is pushed to the SFRPAGE = 011b location. 3. The value (if any) in the SFRPGIDX = 001b location is pushed to the SFRPAGE = 010b location. 4. The current SFRPAGE value is pushed to the SFRPGIDX = 001b location in the stack. 5. SFRPAGE is set to the page corresponding to the flag which generated the interrupt. On a return from interrupt, hardware performs the four following operations: 1. The SFR page stack is popped resulting in the value in the SFRPGIDX = 001b location returning to the SFRPAGE register, thereby restoring the SFR page context without software intervention. 2. The value in the SFRPGIDX = 010b location of the stack is placed in the SFRPGIDX = 001b location. 3. The value in the SFRPGIDX = 011b location of the stack is placed in the SFRPGIDX = 010b location. 4. The value in the SFRPGIDX = 100b location of the stack is placed in the SFRPGIDX = 011b location. Automatic switching of the SFR page by hardware upon interrupt entries and exits may be enabled or dis- abled using the SFR Automatic Page Control Enable Bit (SFRPGEN) located in SFRPGCN. The automatic SFR page switching is enabled after a reset until disabled by firmware. 102 Rev. 1.2

C8051F39x/37x 19.3. SFR Page Stack Example In this example, the SFR Control register is left in the default enabled state (SFRPGEN set to 1), and the core is executing in-line code that is writing values to Temperature Sensor Control Register (TS0CN). The device is also using the SPI peripheral (SPI0) and the Programmable Counter Array (PCA0) peripheral to generate a PWM output. The PCA is timing a critical control function in its interrupt service routine, there- fore, its associated ISR is set to high priority. At this point, the SFR page is set to 0x0F to access the TS0CN SFR. See Figure19.2. SFRPGIDX[2:0] SFRPAGE = 0x0F 000 (TS0CN) 001 SFRSTACK 010 011 100 Figure 19.2. SFR Page Stack While Using SFR Page 0x0F To Access TS0CN Rev. 1.2 103

C8051F39x/37x The SPI0 interrupt occurs while the core executes in-line code by writing a value to TS0CN. The core vec- tors to the SPI0 ISR and pushes the current SFR page value (in this case SFR page 0x0F for TS0CN) into the 001b SFRPGIDX location in the SFR page stack. Also, the core automatically places the SFR page (0x00) needed to access the SPI0’s special function registers into the SFRPAGE register. See Figure19.3. SFRPAGE is considered the top of the SFR page stack. Software may switch to any SFR page by writing a new value to the SFRPAGE register at any time during the SPI0 ISR. SFRPGIDX[2:0] 2)SFRPAGE automatically set to 0x00 on SPI0 interrupt SFRPAGE = 0x00 000 1)SFRPAGE is pushed to (SPIO0) SFRPGIDX = 001b location 0x0F 001 (TS0CN) SFRSTACK 010 011 100 Figure 19.3. SFR Page Stack After SPI0 Interrupt Occurs 104 Rev. 1.2

C8051F39x/37x While in the SPI0 ISR, a PCA interrupt occurs. Recall the PCA interrupt is configured as a high priority interrupt, while the SPI0 interrupt is configured as a low priority interrupt. Thus, the CIP-51 will now vector to the high priority PCA ISR. Upon doing so, the value that was in the SFRPGIDX = 001b location before the PCA interrupt (in this case SFR page 0x0F for TS0CN) is pushed down to the SFRPGIDX = 010b loca- tion. Likewise, the value that was in the SFRPAGE register before the PCA interrupt (SFR page 0x00 for SPI0) is pushed down the stack into the SFRPGIDX = 001b location. Lastly, the CIP-51 will automatically places the SFR page needed to access the PCA0’s special function registers into the SFRPAGE register, SFR page 0x00. See Figure19.4. SFRPGIDX[2:0] 3)SFRPAGE automatically set to 0x00 on PCA0 interrupt SFRPAGE = 0x00 000 2)SFRPAGE is pushed to (PCA0) SFRPGIDX = 001b location 0x00 001 1)Value at SFRPGIDX = 001b location is (SPI0) pushed to SFRPGIDX = 010b location 0x0F SFRSTACK 010 (TS0CN) 011 100 Figure 19.4. SFR Page Stack Upon PCA Interrupt Occurring During a SPI0 ISR Rev. 1.2 105

C8051F39x/37x On exit from the PCA0 interrupt service routine, the CIP-51 will return to the SPI0 ISR. On execution of the RETI instruction, SFR page 0x00 used to access the PCA0 registers will be automatically popped off of the SFR page stack, and the contents at the SFRPGIDX = 001b location will be moved to the SFRPAGE reg- ister. Software in the SPI0 ISR can continue to access SFRs as it did prior to the PCA interrupt. Likewise, the contents at the SFRPGIDX = 010b location are moved to the SFRPGIDX = 001b location. Recall this was the SFR Page value 0x0F being used to access TS0CN before the SPI0 interrupt occurred. See Figure19.5. SFRPGIDX[2:0] 1)SFR page 0x00 from PCA0 ISR automatically popped off on return from interrupt SFRPAGE = 0x00 000 2)Value at SFRPGIDX = 001b location is (SPI0) popped to SFRPAGE 0x0F 001 3)Value at SFRPGIDX = 001b location is (TS0CN) popped to SFRPGIDX = 010b location SFRSTACK 010 011 100 Figure 19.5. SFR Page Stack Upon Return from PCA0 Interrupt 106 Rev. 1.2

C8051F39x/37x On the execution of the RETI instruction in the SPI0 ISR, the value in SFRPAGE register is overwritten with the contents at the SFRPGIDX = 001b location. The CIP-51 may now access the TS0CN register as it did prior to the interrupts occurring. See Figure19.6. SFRPGIDX[2:0] 1)SFR page 0x00 from SPI0 ISR automatically popped off on return from interrupt SFRPAGE = 0x0F 000 2)Value at SFRPGIDX = 001b location is (TS0CN) popped to SFRPAGE 001 SFRSTACK 010 011 100 Figure 19.6. SFR Page Stack Upon Return From SPI0 Interrupt Push operations on the SFR page stack only occur on interrupt service, and pop operations only occur on interrupt exit (execution on the RETI instruction). The automatic switching of the SFRPAGE and operation of the SFR page stack as described above can be disabled in software by clearing the SFR Automatic Page Enable Bit (SFRPGEN) in the SFR Page Control Register (SFRPGCN). Rev. 1.2 107

C8051F39x/37x SFR Definition 19.1. SFRPAGE: SFR Page Bit 7 6 5 4 3 2 1 0 Name SFRPAGE[7:0] Type R/W Reset 0 0 0 0 0 0 0 0 SFR Address=0xA7; SFR Page=All Pages Bit Name Function 7:0 SFRPAGE[7:0] SFR Page Bits. Represents the SFR Page the C8051 core uses when reading or modifying SFRs. Write: Sets the SFR Page. Read: Byte is the SFR page the C8051 core is using. 108 Rev. 1.2

C8051F39x/37x SFR Definition 19.2. SFRPGCN: SFR Page Control Bit 7 6 5 4 3 2 1 0 Name SFRPGIDX[2:0] SFRPGEN Type R/W R/W R/W R/W R/W R/W Reset 0 0 0 0 0 0 0 1 SFR Address=0xCF; SFR Page=All Pages Bit Name Function 7 Reserved Must Write 0b 6:4 SFRPGIDX[2:0] SFR Page Stack Index. This field can be used to access the SFRPAGE values stored in the SFR page stack. It selects which level of the stack is accessi- ble when reading the SFRSTACK register. 000: SFRSTACK contains the value of SFRPAGE, the first/top byte of the SFR page stack 001: SFRSTACK contains the value of the second byte of the SFR page stack 010: SFRSTACK contains the value of the third byte of the SFR page stack 011: SFRSTACK contains the value of the forth byte of the SFR page stack 100: SFRSTACK contains the value of the fifth/bottom byte of the SFR page stack 101: Invalid index 11x: Invalid index 3:1 Reserved Must Write 000b 0 SFRPGEN SFR Automatic Page Control Enable. This bit is used to enable automatic page switching on ISR entry/ exit. When set to 1, the current SFRPAGE value will be pushed onto the SFR page stack, and SFRPAGE will be set to the page corresponding to the flag which generated the interrupt; upon ISR exit, hardware will pop the value from the SFR page stack and restore SFRPAGE. 0: Disable automatic SFR paging. 1: Enable automatic SFR paging. Rev. 1.2 109

C8051F39x/37x SFR Definition 19.3. SFRSTACK: SFR Page Stack Bit 7 6 5 4 3 2 1 0 Name SFRSTACK Type R Reset 0 0 0 0 0 0 0 0 SFR Address=0xD3; SFR Page=F Bit Name Function 7:0 SFRSTACK SFR Page Stack. This register is used to access the contents of the SFR page stack. SFRPGIDX in the SFRPGCN register con- trols which level of the stack this register will access. 110 Rev. 1.2

C8051F39x/37x Table 19.2. Special Function Register (SFR) Memory Map s s e dre ag 0(8) 1(9) 2(A) 3(B) 4(C) 5(D) 6(E) 7(F) d P A F8 SPI0CN PCA0L PCA0H PCA0CPL0 PCA0CPH0 P0MAT P0MASK VDM0CN F0 B P0MDIN P1MDIN P2MDIN CKCON1 EIP1 PCA0PWM E8 ADC0CNPCA0CPL1PCA0CPH1 PCA0CPL2 PCA0CPH2 P1MAT P1MASK RSTSRC 0 SMB0ADM E0 ACC XBR0 XBR1 OSCLCN IT01CF EIE1 F SMB1ADM D8 PCA0CN PCA0MD PCA0CPM0PCA0CPM1 PCA0CPM2 CRC0AUTO CRC0CNT CRC0CN 0 TS0DATL TS0DATH SMB0ADR D0 PSW REF0CN P0SKIP P1SKIP P2SKIP F TS0CN SFRSTACK SMB1ADR TMR2CN TMR2RLL TMR2RLH TMR2L TMR2H C8 REG0CN PCA0CLR SFRPGCN TMR5CN TMR5RLL TMR5RLH TMR5L TMR5H 0 SMB0CN SMB0CF SMB0DAT C0 ADC0GTL ADC0GTH ADC0LTL ADC0LTH SMBTC F SMB1CN SMB1CF SMB1DAT 0 IDA0CN B8 IP AMX0N AMX0P ADC0CF ADC0L ADC0H EIP2 F IDA1CN B0 OSCXCN OSCICN OSCICL PFE0CN FLSCL FLKEY 0 DERIVID REVISION A8 IE CLKSEL EMI0CN EIE2 F SN0 SN1 SN2 SN3 A0 P2 SPI0CFG SPI0CKR SPI0DAT P0MDOUT P1MDOUT P2MDOUT SFRPAGE 98 SCON0 SBUF0 CRC0FLIP CPT0CN CRC0IN CPT0MD CRC0DAT CPT0MX 0 TMR3CN TMR3RLL TMR3RLH TMR3L TMR3H IDA0L IDA0H 90 P1 F TMR4CN TMR4RLL TMR4RLH TMR4L TMR4H IDA1L IDA1H 88 TCON TMOD TL0 TL1 TH0 TH1 CKCON PSCTL 80 P0 SP DPL DPH IPH EIP1H EIP2H PCON 0(8) 1(9) 2(A) 3(B) 4(C) 5(D) 6(E) 7(F) Notes: 1. SFR Addresses ending in 0x0 or 0x8 are bit-addressable locations and can be used with bitwise instructions. 2. Unless indicated otherwise, SFRs are available on both page 0 and page F. Rev. 1.2 111

C8051F39x/37x Table 19.3. Special Function Registers SFRs are listed in alphabetical order. All undefined SFR locations are reserved Register Address SFR Page Description Page ACC 0xE0 All Pages Accumulator 89 ADC0CF 0xBC All Pages ADC0 Configuration 55 ADC0CN 0xE8 All Pages ADC0 Control 57 ADC0GTH 0xC4 All Pages ADC0 Greater-Than Compare High 58 ADC0GTL 0xC3 All Pages ADC0 Greater-Than Compare Low 58 ADC0H 0xBE All Pages ADC0 High 56 ADC0L 0xBD All Pages ADC0 Low 56 ADC0LTH 0xC6 All Pages ADC0 Less-Than Compare Word High 59 ADC0LTL 0xC5 All Pages ADC0 Less-Than Compare Word Low 59 AMX0N 0xBA All Pages AMUX0 Negative Channel Select 63 AMX0P 0xBB All Pages AMUX0 Positive Channel Select 62 B 0xF0 All Pages B Register 90 CKCON 0x8E All Pages Clock Control 243 CKCON1 0xF4 All Pages Clock Control 1 244 CLKSEL 0xA9 All Pages Clock Select 165 CPT0CN 0x9B All Pages Comparator0 Control 78 CPT0MD 0x9D All Pages Comparator0 Mode Selection 79 CPT0MX 0x9F All Pages Comparator0 MUX Selection 81 CRC0AUTO 0xDD All Pages CRC0 Automatic Control 152 CRC0CN 0xDF All Pages CRC0 Control 150 CRC0CNT 0xDE All Pages CRC0 Automatic Flash Sector Count 153 CRC0DAT 0x9E All Pages CRC0 Data Output 151 CRC0FLIP 0x9A All Pages CRC0 Bit Flip 154 CRC0IN 0x9C All Pages CRC0 Data Input 151 DERIVID 0xAB 0 Device Derivative ID 97 DPH 0x83 All Pages Data Pointer High 88 DPL 0x82 All Pages Data Pointer Low 88 EIE1 0xE6 All Pages Extended Interrupt Enable 1 123 EIE2 0xAF All Pages Extended Interrupt Enable 2 126 EIP1 0xF6 All Pages Extended Interrupt Priority 1 124 EIP1H 0x85 All Pages Extended Interrupt Priority 1 High 125 EIP2 0xBF All Pages Extended Interrupt Priority 2 127 EIP2H 0x86 All Pages Extended Interrupt Priority 2 High 127 112 Rev. 1.2

C8051F39x/37x Table 19.3. Special Function Registers (Continued) SFRs are listed in alphabetical order. All undefined SFR locations are reserved Register Address SFR Page Description Page EMI0CN 0xAA All Pages External Memory Interface Control 96 FLKEY 0xB7 All Pages Flash Lock and Key 138 FLSCL 0xB6 All Pages Flash Scale 139 IDA0CN 0xB9 0 Current Mode DAC0 Control 69 IDA0H 0x97 0 Current Mode DAC0 High 70 IDA0L 0x96 0 Current Mode DAC0 Low 70 IDA1CN 0xB9 F Current Mode DAC1 Control 71 IDA1H 0x97 F Current Mode DAC1 High 72 IDA1L 0x96 F Current Mode DAC1 Low 72 IE 0xA8 All Pages Interrupt Enable 120 IP 0xB8 All Pages Interrupt Priority 121 IPH 0x84 All Pages Interrupt Priority High 122 IT01CF 0xE4 All Pages INT0/INT1 Configuration 129 OSCICL 0xB3 All Pages Internal Oscillator Calibration 166 OSCICN 0xB2 All Pages Internal Oscillator Control 167 OSCLCN 0xE3 All Pages Low-Frequency Oscillator Control 168 OSCXCN 0xB1 All Pages External Oscillator Control 172 P0 0x80 All Pages Port 0 Latch 186 P0MASK 0xFE All Pages Port 0 Mask Configuration 183 P0MAT 0xFD All Pages Port 0 Match Configuration 184 P0MDIN 0xF1 All Pages Port 0 Input Mode Configuration 186 P0MDOUT 0xA4 All Pages Port 0 Output Mode Configuration 187 P0SKIP 0xD4 All Pages Port 0 Skip 187 P1 0x90 All Pages Port 1 Latch 188 P1MASK 0xEE All Pages Port 1Mask Configuration 184 P1MAT 0xED All Pages Port 1 Match Configuration 185 P1MDIN 0xF2 All Pages Port 1 Input Mode Configuration 188 P1MDOUT 0xA5 All Pages Port 1 Output Mode Configuration 189 P1SKIP 0xD5 All Pages Port 1 Skip 189 P2 0xA0 All Pages Port 2 Latch 190 P2MDIN 0xF3 All Pages Port 2 Input Mode Configuration 190 P2MDOUT 0xA6 All Pages Port 2 Output Mode Configuration 191 P2SKIP 0xD6 All Pages Port 2 Skip 191 PCA0CLR 0xCE All Pages PCA Comparator Clear Control 293 Rev. 1.2 113

C8051F39x/37x Table 19.3. Special Function Registers (Continued) SFRs are listed in alphabetical order. All undefined SFR locations are reserved Register Address SFR Page Description Page PCA0CN 0xD8 All Pages PCA Control 290 PCA0CPH0 0xFC All Pages PCA Capture 0 High 296 PCA0CPH1 0xEA All Pages PCA Capture 1 High 296 PCA0CPH2 0xEC All Pages PCA Capture 2 High 296 PCA0CPL0 0xFB All Pages PCA Capture 0 Low 296 PCA0CPL1 0xE9 All Pages PCA Capture 1 Low 296 PCA0CPL2 0xEB All Pages PCA Capture 2 Low 296 PCA0CPM0 0xDA All Pages PCA Module 0 Mode Register 294 PCA0CPM1 0xDB All Pages PCA Module 1 Mode Register 294 PCA0CPM2 0xDC All Pages PCA Module 2 Mode Register 294 PCA0H 0xFA All Pages PCA Counter High 295 PCA0L 0xF9 All Pages PCA Counter Low 295 PCA0MD 0xD9 All Pages PCA Mode 291 PCA0PWM 0xF7 All Pages PCA PWM Configuration 292 PCON 0x87 All Pages Power Control 163 PFE0CN 0xB5 All Pages Prefetch Engine Control 92 PSCTL 0x8F All Pages Program Store R/W Control 137 PSW 0xD0 All Pages Program Status Word 91 REF0CN 0xD1 All Pages Voltage Reference Control 74 REG0CN 0xC9 All Pages Voltage Regulator Control 75 REVISION 0xAC 0 Device Revision 98 RSTSRC 0xEF All Pages Reset Source Configuration/Status 160 SBUF0 0x99 All Pages UART0 Data Buffer 226 SCON0 0x98 All Pages UART0 Control 225 SFRPAGE 0xBF All Pages SFR Page 108 SFRPGCN 0xBF All Pages SFR Page Control 109 SFRSTACK 0xBF F SFR Page Stack 110 SMB0ADM 0xE7 0 SMBus0 Slave Address Mask 206 SMB0ADR 0xD7 0 SMBus0 Slave Address 205 SMB0CF 0xC1 0 SMBus0 Configuration 198 SMB0CN 0xC0 0 SMBus0 Control 202 SMB0DAT 0xC2 0 SMBus0 Data 209 SMB1ADM 0xE7 F SMBus1 Slave Address Mask 208 SMB1ADR 0xD7 F SMBus1 Slave Address 207 114 Rev. 1.2

C8051F39x/37x Table 19.3. Special Function Registers (Continued) SFRs are listed in alphabetical order. All undefined SFR locations are reserved Register Address SFR Page Description Page SMB1CF 0xC1 F SMBus1 Configuration 199 SMB1CN 0xC0 F SMBus1 Control 203 SMB1DAT 0xC2 F SMBus1 Data 210 SMBTC 0xC7 All Pages SMBus Timing Control 200 SN0 0xAB F Serial Number Byte 0 100 SN1 0xAC F Serial Number Byte 1 99 SN2 0xAD F Serial Number Byte 2 99 SN3 0xAE F Serial Number Byte 3 98 SP 0x81 All Pages Stack Pointer 89 SPI0CFG 0xA1 All Pages SPI Configuration 235 SPI0CKR 0xA2 All Pages SPI Clock Rate Control 237 SPI0CN 0xF8 All Pages SPI Control 236 SPI0DAT 0xA3 All Pages SPI Data 238 TCON 0x88 All Pages Timer/Counter Control 249 TH0 0x8C All Pages Timer/Counter 0 High 252 TH1 0x8D All Pages Timer/Counter 1 High 252 TL0 0x8A All Pages Timer/Counter 0 Low 251 TL1 0x8B All Pages Timer/Counter 1 Low 251 TMOD 0x89 All Pages Timer/Counter Mode 250 TMR2CN 0xC8 0 Timer/Counter 2 Control 256 TMR2H 0xCD 0 Timer/Counter 2 High 258 TMR2L 0xCC 0 Timer/Counter 2 Low 257 TMR2RLH 0xCB 0 Timer/Counter 2 Reload High 257 TMR2RLL 0xCA 0 Timer/Counter 2 Reload Low 257 TMR3CN 0x91 0 Timer/Counter 3 Control 262 TMR3H 0x95 0 Timer/Counter 3 High 264 TMR3L 0x94 0 Timer/Counter 3 Low 263 TMR3RLH 0x93 0 Timer/Counter 3 Reload High 263 TMR3RLL 0x92 0 Timer/Counter 3 Reload Low 263 TMR4CN 0x91 F Timer/Counter 4 Control 267 TMR4H 0x95 F Timer/Counter 4 High 269 TMR4L 0x94 F Timer/Counter 4 Low 268 TMR4RLH 0x93 F Timer/Counter 4 Reload High 268 TMR4RLL 0x92 F Timer/Counter 4 Reload Low 268 Rev. 1.2 115

C8051F39x/37x Table 19.3. Special Function Registers (Continued) SFRs are listed in alphabetical order. All undefined SFR locations are reserved Register Address SFR Page Description Page TMR5CN 0xC8 F Timer/Counter 5 Control 272 TMR5H 0xCD F Timer/Counter 5 High 274 TMR5L 0xCC F Timer/Counter 5 Low 273 TMR5RLH 0xCB F Timer/Counter 5 Reload High 273 TMR5RLL 0xCA F Timer/Counter 5 Reload Low 273 TS0CN 0xD2 F Temperature Sensor Control 48 TS0DATH 0xD3 0 Temperature Sensor Data High 49 TS0DATL 0xD2 0 Temperature Sensor Data Low 49 VDM0CN 0xFF All Pages VDD Monitor Control 158 XBR0 0xE1 All Pages Port I/O Crossbar Control 0 181 XBR1 0xE2 All Pages Port I/O Crossbar Control 1 182 116 Rev. 1.2

C8051F39x/37x 20. Interrupts The C8051F39x/37x includes an extended interrupt system supporting multiple interrupt sources with four priority levels. The allocation of interrupt sources between on-chip peripherals and external input pins var- ies according to the specific version of the device. Each interrupt source has one or more associated inter- rupt-pending flag(s) located in an SFR. When a peripheral or external source meets a valid interrupt condition, the associated interrupt-pending flag is set to logic1. If interrupts are enabled for the source, an interrupt request is generated when the interrupt-pending flag is set. As soon as execution of the current instruction is complete, the CPU generates an LCALL to a prede- termined address to begin execution of an interrupt service routine (ISR). Each ISR must end with an RETI instruction, which returns program execution to the next instruction that would have been executed if the interrupt request had not occurred. If interrupts are not enabled, the interrupt-pending flag is ignored by the hardware and program execution continues as normal. (The interrupt-pending flag is set to logic1 regard- less of the interrupt's enable/disable state.) Each interrupt source can be individually enabled or disabled through the use of an associated interrupt enable bit in an SFR (IE, EIE1, and EIE2). However, interrupts must first be globally enabled by setting the EA bit (IE.7) to logic1 before the individual interrupt enables are recognized. Setting the EA bit to logic 0 disables all interrupt sources regardless of the individual interrupt-enable settings. Note: Any instruction that clears a bit to disable an interrupt should be immediately followed by an instruc- tion that has two or more opcode bytes. Using EA (global interrupt enable) as an example: // in 'C': EA = 0; // clear EA bit. EA = 0; // this is a dummy instruction with two-byte opcode. ; in assembly: CLR EA ; clear EA bit. CLR EA ; this is a dummy instruction with two-byte opcode. For example, if an interrupt is posted during the execution phase of a "CLR EA" opcode (or any instruction which clears a bit to disable an interrupt source), and the instruction is followed by a single-cycle instruc- tion, the interrupt may be taken. However, a read of the enable bit will return a '0' inside the interrupt ser- vice routine. When the bit-clearing opcode is followed by a multi-cycle instruction, the interrupt will not be taken. Some interrupt-pending flags are automatically cleared by the hardware when the CPU vectors to the ISR. However, most are not cleared by the hardware and must be cleared by software before returning from the ISR. If an interrupt-pending flag remains set after the CPU completes the return-from-interrupt (RETI) instruction, a new interrupt request will be generated immediately and the CPU will re-enter the ISR after the completion of the next instruction. Rev. 1.2 117

C8051F39x/37x 20.1. MCU Interrupt Sources and Vectors The C8051F39x/37x MCUs support 18 interrupt sources. Software can simulate an interrupt by setting any interrupt-pending flag to logic1. If interrupts are enabled for the flag, an interrupt request will be generated and the CPU will vector to the ISR address associated with the interrupt-pending flag. MCU interrupt sources, associated vector addresses, priority order and control bits are summarized in Table20.2. Refer to the datasheet section associated with a particular on-chip peripheral for information regarding valid interrupt conditions for the peripheral and the behavior of its interrupt-pending flag(s). 20.1.1. Interrupt Priorities Each interrupt source can be individually programmed to one of four priority levels. This differs from the traditional two priority levels on the 8051 core. However, the implementation of the extra levels is back- wards-compatible with legacy 8051 code. An interrupt service routine can be preempted by any interrupt of higher priority. Interrupts at the highest priority level cannot be preempted. Each interrupt has two associated priority bits which are used to config- ure the priority level. For backwards compatibility, the bits are spread across two different registers. The LSBs of the priority setting are stored in the IP, EIP1 and EIP2 registers, while the MSBs are store in the IPH, EIP1H and EIP2H registers. Priority levels according to the MSB and LSB are decoded in Table20.1. The lowest priority setting is the default for all interrupts. If two or more interrupts are recognized simulta- neously, the interrupt with the highest priority is serviced first. If both interrupts have the same priority level, a fixed priority order is used to arbitrate, given in Table20.2. If legacy 8051 operation is desired, the bits of the “High” priority registers (IPH, EIP1H and EIP2H) should all be configured to 0 (this is the reset value of these registers). Priority MSB Priority LSB Priority Level (from IPH, EIP1H or (from IP, EIP1 or EIP2H) EIP2) 0 0 Priority 0 (lowest priority, default) 0 1 Priority 1 1 0 Priority 2 1 1 Priority 3 (highest priority) Table 20.1. Configurable Interrupt Priority Decoding 20.1.2. Interrupt Latency Interrupt response time depends on the state of the CPU when the interrupt occurs. Pending interrupts are sampled and priority decoded each system clock cycle. Therefore, the fastest possible response time is 5 system clock cycles: 1clock cycle to detect the interrupt and 4clock cycles to complete the LCALL to the ISR. If an interrupt is pending when a RETI is executed, a single instruction is executed before an LCALL is made to service the pending interrupt. Therefore, the maximum response time for an interrupt (when no other interrupt is currently being serviced or the new interrupt is of greater priority) occurs when the CPU is performing an RETI instruction followed by a DIV as the next instruction. In this case, the response time is 18system clock cycles: 1clock cycle to detect the interrupt, 5clock cycles to execute the RETI, 8clock cycles to complete the DIV instruction and 4clock cycles to execute the LCALL to the ISR. If the CPU is executing an ISR for an interrupt with equal or higher priority, the new interrupt will not be serviced until the current ISR completes, including the RETI and following instruction. If more than one interrupt is pending when the CPU exits an ISR, the CPU will service the next highest priority interrupt that is pending. 118 Rev. 1.2

C8051F39x/37x Table 20.2. Interrupt Summary Interrupt Source Interrupt Priority Pending Flags e? ? Enable Flag Vector Order bl W a H ss y e b dr d d re a a t e Bi Cl Reset 0x0000 Top None N/A N/A Always Enabled External Interrupt 0 (INT0) 0x0003 0 IE0 (TCON.1) Y Y EX0 (IE.0) Timer 0 Overflow 0x000B 1 TF0 (TCON.5) Y Y ET0 (IE.1) External Interrupt 1 (INT1) 0x0013 2 IE1 (TCON.3) Y Y EX1 (IE.2) Timer 1 Overflow 0x001B 3 TF1 (TCON.7) Y Y ET1 (IE.3) UART0 0x0023 4 RI0 (SCON0.0) Y N ES0 (IE.4) TI0 (SCON0.1) Timer 2 Overflow 0x002B 5 TF2H (TMR2CN.7) Y N ET2 (IE.5) TF2L (TMR2CN.6) SPI0 0x0033 6 SPIF (SPI0CN.7) Y N ESPI0 (IE.6) WCOL (SPI0CN.6) MODF (SPI0CN.5) RXOVRN (SPI0CN.4) SMB0 0x003B 7 SI (SMB0CN.0) Y N ESMB0 (EIE1.0) Port Match 0x0043 8 None N/A N/A EMAT (EIE1.1) ADC0 Window Compare 0x004B 9 AD0WINT (ADC0CN.3) Y N EWADC0 (EIE1.2) ADC0 Conversion Com- 0x0053 10 AD0INT (ADC0CN.5) Y N EADC0 (EIE1.3) plete Programmable Counter 0x005B 11 CF (PCA0CN.7) Y N EPCA0 (EIE1.4) Array CCFn (PCA0CN.n) COVF (PCA0PWM.6) Comparator0 0x0063 12 CP0FIF (CPT0CN.4) N N ECP0 (EIE1.5) CP0RIF (CPT0CN.5) Reserved 0x006B 13 N/A N/A N/A N/A Timer 3 Overflow 0x0073 14 TF3H (TMR3CN.7) N N ET3 (EIE1.7) TF3L (TMR3CN.6) SMB1 0x007B 15 SI (SMB0CN.0) Y N ESMB0 (EIE2.0) Timer 4 Overflow 0x0083 16 TF4H (TMR4CN.7) Y N ET4 (EIE2.1) TF4L (TMR4CN.6) Timer 5 Overflow 0x008B 17 TF5H (TMR5CN.7) N N ET5 (EIE2.2) TF5L (TMR5CN.6) Precision Temp Sensor 0x0093 18 TS0DN (TS0CN.6) N N EPTS (EIE2.3) Rev. 1.2 119

C8051F39x/37x 20.2. Interrupt Register Descriptions The SFRs used to enable the interrupt sources and set their priority level are described in this section. Refer to the data sheet section associated with a particular on-chip peripheral for information regarding valid interrupt conditions for the peripheral and the behavior of its interrupt-pending flag(s). SFR Definition 20.1. IE: Interrupt Enable Bit 7 6 5 4 3 2 1 0 Name EA ESPI0 ET2 ES0 ET1 EX1 ET0 EX0 Type R/W R/W R/W R/W R/W R/W R/W R/W Reset 0 0 0 0 0 0 0 0 SFR Address=0xA8; SFR Page=All Pages; Bit-Addressable Bit Name Function 7 EA Enable All Interrupts. Globally enables/disables all interrupts. It overrides individual interrupt mask settings. 0: Disable all interrupt sources. 1: Enable each interrupt according to its individual mask setting. 6 ESPI0 Enable Serial Peripheral Interface (SPI0) Interrupt. This bit sets the masking of the SPI0 interrupts. 0: Disable all SPI0 interrupts. 1: Enable interrupt requests generated by SPI0. 5 ET2 Enable Timer2 Interrupt. This bit sets the masking of the Timer2 interrupt. 0: Disable Timer2 interrupt. 1: Enable interrupt requests generated by the TF2L or TF2H flags. 4 ES0 Enable UART0 Interrupt. This bit sets the masking of the UART0 interrupt. 0: Disable UART0 interrupt. 1: Enable UART0 interrupt. 3 ET1 Enable Timer1 Interrupt. This bit sets the masking of the Timer1 interrupt. 0: Disable all Timer1 interrupt. 1: Enable interrupt requests generated by the TF1 flag. 2 EX1 Enable External Interrupt 1. This bit sets the masking of External Interrupt 1. 0: Disable external interrupt 1. 1: Enable interrupt requests generated by the /INT1 input. 1 ET0 Enable Timer0 Interrupt. This bit sets the masking of the Timer0 interrupt. 0: Disable all Timer0 interrupt. 1: Enable interrupt requests generated by the TF0 flag. 0 EX0 Enable External Interrupt 0. This bit sets the masking of External Interrupt 0. 0: Disable external interrupt 0. 1: Enable interrupt requests generated by the INT0 input. 120 Rev. 1.2

C8051F39x/37x SFR Definition 20.2. IP: Interrupt Priority Bit 7 6 5 4 3 2 1 0 Name PSPI0 PT2 PS0 PT1 PX1 PT0 PX0 Type R R/W R/W R/W R/W R/W R/W R/W Reset 1 0 0 0 0 0 0 0 SFR Address=0xB8; SFR Page=All Pages; Bit-Addressable Bit Name Function 7 Unused Read=1, Write=Don't Care. 6 PSPI0 Serial Peripheral Interface (SPI0) Interrupt Priority Control LSB. This bit sets the LSB of the priority field for the SPI0 interrupt. 5 PT2 Timer 2 Interrupt Priority Control LSB. This bit sets the LSB of the priority field for the Timer 2 interrupt. 4 PS0 UART0 Interrupt Priority Control LSB. This bit sets the LSB of the priority field for the UART0 interrupt. 3 PT1 Timer 1 Interrupt Priority Control LSB. This bit sets the LSB of the priority field for the Timer 1 interrupt. 2 PX1 External Interrupt 1 Priority Control LSB. This bit sets the LSB of the priority field for the External Interrupt 1 interrupt. 1 PT0 Timer 0 Interrupt Priority Control LSB. This bit sets the LSB of the priority field for the Timer 0 interrupt. 0 PX0 External Interrupt 0 Priority Control LSB. This bit sets the LSB of the priority field for the External Interrupt 0 interrupt. Rev. 1.2 121

C8051F39x/37x SFR Definition 20.3. IPH: Interrupt Priority High Bit 7 6 5 4 3 2 1 0 Name PHSPI0 PHT2 PHS0 PHT1 PHX1 PHT0 PHX0 Type R R/W R/W R/W R/W R/W R/W R/W Reset 1 0 0 0 0 0 0 0 SFR Address=0x84; SFR Page=All Pages; Bit-Addressable Bit Name Function 7 Unused Read=1, Write=Don't Care. 6 PHSPI0 Serial Peripheral Interface (SPI0) Interrupt Priority Control MSB. This bit sets the MSB of the priority field for the SPI0 interrupt. 5 PHT2 Timer 2 Interrupt Priority Control MSB. This bit sets the MSB of the priority field for the Timer 2 interrupt. 4 PHS0 UART0 Interrupt Priority Control MSB. This bit sets the MSB of the priority field for the UART0 interrupt. 3 PHT1 Timer 1 Interrupt Priority Control MSB. This bit sets the MSB of the priority field for the Timer 1 interrupt. 2 PHX1 External Interrupt 1 Priority Control MSB. This bit sets the MSB of the priority field for the External Interrupt 1 inter- rupt. 1 PHT0 Timer 0 Interrupt Priority Control MSB. This bit sets the MSB of the priority field for the Timer 0 interrupt. 0 PHX0 External Interrupt 0 Priority Control MSB. This bit sets the MSB of the priority field for the External Interrupt 0 inter- rupt. 122 Rev. 1.2

C8051F39x/37x SFR Definition 20.4. EIE1: Extended Interrupt Enable 1 Bit 7 6 5 4 3 2 1 0 Name ET3 ECP0 EPCA0 EADC0 EWADC0 EMAT ESMB0 Type R/W R/W R/W R/W R/W R/W R/W R/W Reset 0 0 0 0 0 0 0 0 SFR Address=0xE6; SFR Page=All Pages Bit Name Function 7 ET3 Enable Timer3 Interrupt. This bit sets the masking of the Timer3 interrupt. 0: Disable Timer3 interrupts. 1: Enable interrupt requests generated by the TF3L or TF3H flags. 6 Reserved Reserved. Must Write 0. 5 ECP0 Enable Comparator0 (CP0) Interrupt. This bit sets the masking of the CP0 interrupt. 0: Disable CP0 interrupts. 1: Enable interrupt requests generated by the CP0RIF or CP0FIF flags. 4 EPCA0 Enable Programmable Counter Array (PCA0) Interrupt. This bit sets the masking of the PCA0 interrupts. 0: Disable all PCA0 interrupts. 1: Enable interrupt requests generated by PCA0. 3 EADC0 Enable ADC0 Conversion Complete Interrupt. This bit sets the masking of the ADC0 Conversion Complete interrupt. 0: Disable ADC0 Conversion Complete interrupt. 1: Enable interrupt requests generated by the AD0INT flag. 2 EWADC0 Enable Window Comparison ADC0 Interrupt. This bit sets the masking of ADC0 Window Comparison interrupt. 0: Disable ADC0 Window Comparison interrupt. 1: Enable interrupt requests generated by ADC0 Window Compare flag (AD0WINT). 1 EMAT Enable Port Match Interrupts. This bit sets the masking of the Port Match Event interrupt. 0: Disable all Port Match interrupts. 1: Enable interrupt requests generated by a Port Match. 0 ESMB0 Enable SMBus (SMB0) Interrupt. This bit sets the masking of the SMB0 interrupt. 0: Disable all SMB0 interrupts. 1: Enable interrupt requests generated by SMB0. Rev. 1.2 123

C8051F39x/37x SFR Definition 20.5. EIP1: Extended Interrupt Priority 1 Bit 7 6 5 4 3 2 1 0 Name PT3 PCP0 PPCA0 PADC0 PWADC0 PMAT PSMB0 Type R/W R/W R/W R/W R/W R/W R/W R/W Reset 0 0 0 0 0 0 0 0 SFR Address=0xF6; SFR Page=All Pages Bit Name Function 7 PT3 Timer3 Interrupt Priority Control LSB. This bit sets the LSB of the priority field for the Timer3 interrupt. 6 Reserved Reserved. Must Write 0. 5 PCP0 Comparator0 (CP0) Interrupt Priority Control LSB. This bit sets the LSB of the priority field for the CP0 interrupt. 4 PPCA0 Programmable Counter Array (PCA0) Interrupt Priority Control LSB. This bit sets the LSB of the priority field for the PCA0 interrupt. 3 PADC0 ADC0 Conversion Complete Interrupt Priority Control LSB. This bit sets the LSB of the priority field for the ADC0 Conversion Complete interrupt. 2 PWADC0 ADC0 Window Comparator Interrupt Priority Control LSB. This bit sets the LSB of the priority field for the ADC0 Window interrupt. 1 PMAT Port Match Interrupt Priority Control LSB. This bit sets the LSB of the priority field for the Port Match Event interrupt. 0 PSMB0 SMBus (SMB0) Interrupt Priority Control LSB. This bit sets the LSB of the priority field for the SMB0 interrupt. 124 Rev. 1.2

C8051F39x/37x SFR Definition 20.6. EIP1H: Extended Interrupt Priority 1 High Bit 7 6 5 4 3 2 1 0 Name PHT3 PHCP0 PHPCA0 PHADC0 PHWADC0 PHMAT PHSMB0 Type R/W R/W R/W R/W R/W R/W R/W R/W Reset 0 0 0 0 0 0 0 0 SFR Address=0x85; SFR Page=All Pages Bit Name Function 7 PHT3 Timer3 Interrupt Priority Control MSB. This bit sets the MSB of the priority field for the Timer3 interrupt. 6 Reserved Reserved. Must Write 0. 5 PHCP0 Comparator0 (CP0) Interrupt Priority Control MSB. This bit sets the MSB of the priority field for the CP0 interrupt. 4 PHPCA0 Programmable Counter Array (PCA0) Interrupt Priority Control MSB. This bit sets the MSB of the priority field for the PCA0 interrupt. 3 PHADC0 ADC0 Conversion Complete Interrupt Priority Control MSB. This bit sets the MSB of the priority field for the ADC0 Conversion Complete interrupt. 2 PHWADC0 ADC0 Window Comparator Interrupt Priority Control MSB. This bit sets the MSB of the priority field for the ADC0 Window interrupt. 1 PHMAT Port Match Interrupt Priority Control MSB. This bit sets the MSB of the priority field for the Port Match Event interrupt. 0 PHSMB0 SMBus (SMB0) Interrupt Priority Control MSB. This bit sets the MSB of the priority field for the SMB0 interrupt. Rev. 1.2 125

C8051F39x/37x SFR Definition 20.7. EIE2: Extended Interrupt Enable 2 Bit 7 6 5 4 3 2 1 0 Name EPTS ET5 ET4 ESMB1 Type R/W R/W R/W R/W R/W R/W R/W R/W Reset 0 0 0 0 0 0 0 0 SFR Address=0xAF; SFR Page=All Pages Bit Name Function 7:4 Reserved Must Write 0000b. 3 EPTS Enable Precision Temperature Sensor Interrupt. This bit sets the masking of the Precision Temperature Sensor interrupt. 0: Disable Precision Temperature Sensor interrupts. 1: Enable interrupt requests generated by the Precision Tempera- ture Sensor. 2 ET5 Enable Timer5 Interrupt. This bit sets the masking of the Timer5 interrupt. 0: Disable Timer5 interrupts. 1: Enable interrupt requests generated by the TF5L or TF5H flags. 1 ET4 Enable Timer4 Interrupt. This bit sets the masking of the Timer4 interrupt. 0: Disable Timer4 interrupts. 1: Enable interrupt requests generated by the TF4L or TF4H flags. 0 ESMB1 Enable SMBus (SMB1) Interrupt. This bit sets the masking of the SMB1 interrupt. 0: Disable all SMB1 interrupts. 1: Enable interrupt requests generated by SMB1. 126 Rev. 1.2

C8051F39x/37x SFR Definition 20.8. EIP2: Extended Interrupt Priority 2 Bit 7 6 5 4 3 2 1 0 Name PPTS PT5 PT4 PSMB1 Type R/W R/W R/W R/W R/W R/W R/W R/W Reset 0 0 0 0 0 0 0 0 SFR Address=0xBF; SFR Page=All Pages Bit Name Function 7:4 Reserved Must Write 0000b. 3 PPTS Precision Temperature Sensor Interrupt Priority Control LSB. This bit sets the LSB of the priority field for the Precision Tempera- ture Sensor interrupt. 2 PT5 Timer5 Interrupt Priority Control LSB. This bit sets the LSB of the priority field for the Timer5 interrupt. 1 PT4 Timer4 Interrupt Priority Control LSB. This bit sets the LSB of the priority field for the Timer4 interrupt. 0 PSMB1 SMBus (SMB1) Interrupt Priority Control LSB. This bit sets the LSB of the priority field for the SMB1 interrupt. SFR Definition 20.9. EIP2H: Extended Interrupt Priority 2 High Bit 7 6 5 4 3 2 1 0 Name PHPTS PHT5 PHT4 PHSMB1 Type R/W R/W R/W R/W R/W R/W R/W R/W Reset 0 0 0 0 0 0 0 0 SFR Address=0x86; SFR Page=All Pages Bit Name Function 7:4 Reserved Must Write 0000b. 3 PHPTS Precision Temperature Sensor Interrupt Priority Control MSB. This bit sets the MSB of the priority field for the Precision Tem- perature Sensor interrupt. 2 PHT5 Timer5 Interrupt Priority Control MSB. This bit sets the MSB of the priority field for the Timer5 interrupt. 1 PHT4 Timer4 Interrupt Priority Control MSB. This bit sets the MSB of the priority field for the Timer4 interrupt. 0 PHSMB1 SMBus (SMB1) Interrupt Priority Control MSB. This bit sets the MSB of the priority field for the SMB1 interrupt. Rev. 1.2 127

C8051F39x/37x 20.3. External Interrupts INT0 and INT1 The INT0 and INT1 external interrupt sources are configurable as active high or low, edge or level sensi- tive. The IN0PL (INT0 Polarity) and IN1PL (INT1 Polarity) bits in the IT01CF register select active high or active low; the IT0 and IT1 bits in TCON (Section “31.1.Timer 0 and Timer 1” on page245) select level or edge sensitive. The table below lists the possible configurations. IT0 IN0PL INT0 Interrupt IT1 IN1PL INT1 Interrupt 1 0 Active low, edge sensitive 1 0 Active low, edge sensitive 1 1 Active high, edge sensitive 1 1 Active high, edge sensitive 0 0 Active low, level sensitive 0 0 Active low, level sensitive 0 1 Active high, level sensitive 0 1 Active high, level sensitive INT0 and INT1 are assigned to Port pins as defined in the IT01CF register (see SFR Definition 20.10). Note that INT0 and INT1 Port pin assignments are independent of any Crossbar assignments. INT0 and INT1 will monitor their assigned Port pins without disturbing the peripheral that was assigned the Port pin via the Crossbar. To assign a Port pin only to INT0 and/or INT1, configure the Crossbar to skip the selected pin(s). This is accomplished by setting the associated bit in register XBR0 (see Section “27.3.Priority Crossbar Decoder” on page178 for complete details on configuring the Crossbar). IE0 (TCON.1) and IE1 (TCON.3) serve as the interrupt-pending flags for the INT0 and INT1 external inter- rupts, respectively. If an INT0 or INT1 external interrupt is configured as edge-sensitive, the corresponding interrupt-pending flag is automatically cleared by the hardware when the CPU vectors to the ISR. When configured as level sensitive, the interrupt-pending flag remains logic 1 while the input is active as defined by the corresponding polarity bit (IN0PL or IN1PL); the flag remains logic 0 while the input is inactive. The external interrupt source must hold the input active until the interrupt request is recognized. It must then deactivate the interrupt request before execution of the ISR completes or another interrupt request will be generated. 128 Rev. 1.2

C8051F39x/37x SFR Definition 20.10. IT01CF: INT0/INT1 Configuration Bit 7 6 5 4 3 2 1 0 Name IN1PL IN1SL[2:0] IN0PL IN0SL[2:0] Type R/W R/W R/W R/W Reset 0 0 0 0 0 0 0 1 SFR Address=0xE4; SFR Page=All Pages Rev. 1.2 129

C8051F39x/37x Bit Name Function 7 IN1PL INT1 Polarity. 0: /INT1 input is active low. 1: /INT1 input is active high. 6:4 IN1SL[2:0] INT1 Port Pin Selection Bits. These bits select which Port pin is assigned to /INT1. Note that this pin assignment is independent of the Crossbar; /INT1 will monitor the assigned Port pin without disturbing the peripheral that has been assigned the Port pin via the Crossbar. The Cross- bar will not assign the Port pin to a peripheral if it is configured to skip the selected pin. 000: Select P0.0 001: Select P0.1 010: Select P0.2 011: Select P0.3 100: Select P0.4 101: Select P0.5 110: Select P0.6 111: Select P0.7 3 IN0PL INT0 Polarity. 0: INT0 input is active low. 1: INT0 input is active high. 2:0 IN0SL[2:0] INT0 Port Pin Selection Bits. These bits select which Port pin is assigned to INT0. Note that this pin assignment is independent of the Crossbar; INT0 will monitor the assigned Port pin without disturbing the peripheral that has been assigned the Port pin via the Crossbar. The Cross- bar will not assign the Port pin to a peripheral if it is configured to skip the selected pin. 000: Select P0.0 001: Select P0.1 010: Select P0.2 011: Select P0.3 100: Select P0.4 101: Select P0.5 110: Select P0.6 111: Select P0.7 130 Rev. 1.2

C8051F39x/37x 21. Flash Memory On-chip, re-programmable Flash memory is included for program code and non-volatile data storage. The Flash memory can be programmed in-system, a single byte at a time, through the C2 interface or by soft- ware using the MOVX instruction. Once cleared to logic0, a Flash bit must be erased to set it back to logic1. Flash bytes would typically be erased (set to 0xFF) before being reprogrammed. The write and erase operations are automatically timed by hardware for proper execution; data polling to determine the end of the write/erase operation is not required. Code execution is stalled during a Flash write/erase oper- ation. Refer to Section “7.Electrical Characteristics” on page32 for complete Flash memory electrical characteristics. 21.1. Programming The Flash Memory The simplest means of programming the Flash memory is through the C2 interface using programming tools provided by Silicon Labs or a third party vendor. This is the only means for programming a non-initial- ized device. For details on the C2 commands to program Flash memory, see Section “33.C2 Interface” on page297. To ensure the integrity of Flash contents, it is strongly recommended that the on-chip V Monitor be DD enabled in any system that includes code that writes and/or erases Flash memory from software. See Sec- tion 21.4 for more details. 21.1.1. Flash Lock and Key Functions Flash writes and erases by user software are protected with a lock and key function. The Flash Lock and Key Register (FLKEY) must be written with the correct key codes, in sequence, before Flash operations may be performed. The key codes are: 0xA5, 0xF1. The timing does not matter, but the codes must be written in order. If the key codes are written out of order, or the wrong codes are written, Flash writes and erases will be disabled until the next system reset. Flash writes and erases will also be disabled if a Flash write or erase is attempted before the key codes have been written properly. The Flash lock resets after each write or erase; the key codes must be written again before a following Flash operation can be per- formed. The FLKEY register is detailed in SFR Definition 21.2. 21.1.2. Flash Erase Procedure The Flash memory can be programmed by software using the MOVX write instruction with the address and data byte to be programmed provided as normal operands. Before writing to Flash memory using MOVX, Flash write operations must be enabled by: (1) setting the PSWE Program Store Write Enable bit (PSCTL.0) to logic1 (this directs the MOVX writes to target Flash memory); and (2) Writing the Flash key codes in sequence to the Flash Lock register (FLKEY). The PSWE bit remains set until cleared by soft- ware. A write to Flash memory can clear bits to logic 0 but cannot set them; only an erase operation can set bits to logic 1 in Flash. A byte location to be programmed should be erased before a new value is written. The Flash memory is organized in 512-byte pages. The erase operation applies to an entire page (setting all bytes in the page to 0xFF). To erase an entire 512-byte page, perform the following steps: 1. Disable interrupts (recommended). 2. Set thePSEE bit (register PSCTL). 3. Set the PSWE bit (register PSCTL). 4. Write the first key code to FLKEY: 0xA5. 5. Write the second key code to FLKEY: 0xF1. 6. Using the MOVX instruction, write a data byte to any location within the 512-byte page to be erased. 7. Clear the PSWE and PSEE bits. Rev. 1.2 131

C8051F39x/37x 21.1.3. Flash Write Procedure Flash bytes are programmed by software with the following sequence: 1. Disable interrupts (recommended). 2. Erase the 512-byte Flash page containing the target location, as described in Section 21.1.2. 3. Set the PSWE bit (register PSCTL). 4. Clear the PSEE bit (register PSCTL). 5. Write the first key code to FLKEY: 0xA5. 6. Write the second key code to FLKEY: 0xF1. 7. Using the MOVX instruction, write a single data byte to the desired location within the 512-byte sector. 8. Clear the PSWE bit. Steps 5–7 must be repeated for each byte to be written. After Flash writes are complete, PSWE should be cleared so that MOVX instructions do not target program memory. 21.2. Non-volatile Data Storage The Flash memory can be used for non-volatile data storage as well as program code. This allows data such as calibration coefficients to be calculated and stored at run time. Data is written using the MOVX write instruction and read using the MOVC instruction. Note: MOVX read instructions always target XRAM. 132 Rev. 1.2

C8051F39x/37x 21.3. Security Options The CIP-51 provides security options to protect the Flash memory from inadvertent modification by soft- ware as well as to prevent the viewing of proprietary program code and constants. The Program Store Write Enable (bit PSWE in register PSCTL) and the Program Store Erase Enable (bit PSEE in register PSCTL) bits protect the Flash memory from accidental modification by software. PSWE must be explicitly set to ‘1’ before software can modify the Flash memory; both PSWE and PSEE must be set to ‘1’ before software can erase Flash memory. Additional security features prevent proprietary program code and data constants from being read or altered across the C2 interface. A Security Lock Byte located in Flash user space offers protection of the Flash program memory from access (reads, writes, or erases) by unprotected code or the C2 interface. See Section “17.Memory Orga- nization” on page93 for the location of the security byte. The Flash security mechanism allows the user to lock n512-byte Flash pages, starting at page 0 (addresses 0x0000 to 0x01FF), where n is the 1’s comple- ment number represented by the Security Lock Byte. Note that the page containing the Flash Security Lock Byte is unlocked when no other Flash pages are locked (all bits of the Lock Byte are ‘1’) and locked when any other Flash pages are locked (any bit of the Lock Byte is ‘0’). An example is shown in Figure21.1. Security Lock Byte: 11111101b 1s Complement: 00000010b Flash pages locked: 3 (First two Flash pages + Lock Byte Page) Figure 21.1. Security Byte Decoding The level of Flash security depends on the Flash access method. The three Flash access methods that can be restricted are reads, writes, and erases from the C2 debug interface, user firmware executing on unlocked pages, and user firmware executing on locked pages. Table21.1 summarizes the Flash security features of the C8051F39x/37x devices. Table 21.1. Flash Security Summary Action C2 Debug User Firmware executing from: Interface an unlocked page a locked page Read, Write or Erase unlocked pages Permitted Permitted Permitted (except page with Lock Byte) Read, Write or Erase locked pages Not Permitted Flash Error Reset Permitted (except page with Lock Byte) Read or Write page containing Lock Byte Permitted Permitted Permitted (if no pages are locked) Read or Write page containing Lock Byte Not Permitted Flash Error Reset Permitted (if any page is locked) Read contents of Lock Byte Permitted Permitted Permitted (if no pages are locked) Read contents of Lock Byte Not Permitted Flash Error Reset Permitted (if any page is locked) Erase page containing Lock Byte Permitted Permitted N/A (if no pages are locked) Rev. 1.2 133

C8051F39x/37x Table 21.1. Flash Security Summary Erase page containing Lock Byte—Unlock all C2 Device Flash Error Reset Flash Error Reset pages (if any page is locked) Erase Only Lock additional pages Not Permitted Flash Error Reset Flash Error Reset (change 1s to 0s in the Lock Byte) Unlock individual pages Not Permitted Flash Error Reset Flash Error Reset (change 0s to 1s in the Lock Byte) Read, Write or Erase Reserved Area Not Permitted Flash Error Reset Flash Error Reset C2 Device Erase—Erases all Flash pages including the page containing the Lock Byte. Flash Error Reset —Not permitted; Causes Flash Error Device Reset (FERROR bit in RSTSRC is '1' after reset). - All prohibited operations that are performed via the C2 interface are ignored (do not cause device reset). - Locking any Flash page also locks the page containing the Lock Byte. - Once written to, the Lock Byte cannot be modified except by performing a C2 Device Erase. - If user code writes to the Lock Byte, the Lock does not take effect until the next device reset. 134 Rev. 1.2

C8051F39x/37x 21.4. Flash Write and Erase Guidelines Any system which contains routines which write or erase Flash memory from software involves some risk that the write or erase routines will execute unintentionally if the CPU is operating outside its specified operating range of V , system clock frequency, or temperature. This accidental execution of Flash modi- DD fying code can result in alteration of Flash memory contents causing a system failure that is only recover- able by re-Flashing the code in the device. The following guidelines are recommended for any system which contains routines which write or erase Flash from code. 21.4.1. V Maintenance and the V Monitor DD DD 1. If the system power supply is subject to voltage or current "spikes," add sufficient transient protection devices to the power supply to ensure that the supply voltages listed in the Absolute Maximum Ratings table are not exceeded. 2. Make certain that the minimum V rise time specification of 1 ms is met. If the system cannot meet DD this rise time specification, then add an external V brownout circuit to the RST pin of the device that DD holds the device in reset until V reaches 2.7V and re-asserts RST if V drops below 2.7V. DD DD 3. Enable the on-chip V monitor and enable the V monitor as a reset source as early in code as DD DD possible. This should be the first set of instructions executed after the Reset Vector. For 'C'-based systems, this will involve modifying the startup code added by the C compiler. See your compiler documentation for more details. Make certain that there are no delays in software between enabling the V monitor and enabling the V monitor as a reset source. Code examples showing this can be DD DD found in “AN201: Writing to Flash from Firmware", available from the Silicon Laboratories web site. 4. As an added precaution, explicitly enable the V monitor and enable the V monitor as a reset DD DD source inside the functions that write and erase Flash memory. The V monitor enable instructions DD should be placed just after the instruction to set PSWE to a 1, but before the Flash write or erase operation instruction. 5. Make certain that all writes to the RSTSRC (Reset Sources) register use direct assignment operators and explicitly DO NOT use the bit-wise operators (such as AND or OR). For example, "RSTSRC=0x02" is correct. "RSTSRC |= 0x02" is incorrect. 6. Make certain that all writes to the RSTSRC register explicitly set the PORSF bit to a '1'. Areas to check are initialization code which enables other reset sources, such as the Missing Clock Detector or Comparator, for example, and instructions which force a Software Reset. A global search on "RSTSRC" can quickly verify this. 21.4.2. PSWE Maintenance 7. Reduce the number of places in code where the PSWE bit (b0 in PSCTL) is set to a '1'. There should be exactly one routine in code that sets PSWE to a '1' to write Flash bytes and one routine in code that sets PSWE and PSEE both to a '1' to erase Flash pages. 8. Minimize the number of variable accesses while PSWE is set to a '1'. Handle pointer address updates and loop variable maintenance outside the "PSWE=1;... PSWE=0;" area. Code examples showing this can be found in “AN201: Writing to Flash from Firmware", available from the Silicon Laboratories web site. 9. Disable interrupts prior to setting PSWE to a '1' and leave them disabled until after PSWE has been reset to 0. Any interrupts posted during the Flash write or erase operation will be serviced in priority order after the Flash operation has been completed and interrupts have been re-enabled by software. 10.Make certain that the Flash write and erase pointer variables are not located in XRAM. See your compiler documentation for instructions regarding how to explicitly locate variables in different memory areas. 11.Add address bounds checking to the routines that write or erase Flash memory to ensure that a routine called with an illegal address does not result in modification of the Flash. Rev. 1.2 135

C8051F39x/37x 21.4.3. System Clock 12.If operating from an external crystal, be advised that crystal performance is susceptible to electrical interference and is sensitive to layout and to changes in temperature. If the system is operating in an electrically noisy environment, use the internal oscillator or use an external CMOS clock. 13.If operating from the external oscillator, switch to the internal oscillator during Flash write or erase operations. The external oscillator can continue to run, and the CPU can switch back to the external oscillator after the Flash operation has completed. Additional Flash recommendations and example code can be found in “AN201: Writing to Flash from Firm- ware", available from the Silicon Laboratories web site. 136 Rev. 1.2

C8051F39x/37x SFR Definition 21.1. PSCTL: Program Store R/W Control Bit 7 6 5 4 3 2 1 0 Name PSEE PSWE Type R R R R R R R/W R/W Reset 0 0 0 0 0 0 0 0 SFR Address=0x8F; SFR Page=All Pages Bit Name Function 7:2 Unused Read=000000b, Write=don’t care. 1 PSEE Program Store Erase Enable Setting this bit (in combination with PSWE) allows an entire page of Flash program memory to be erased. If this bit is logic 1 and Flash writes are enabled (PSWE is logic 1), a write to Flash mem- ory using the MOVX instruction will erase the entire page that con- tains the location addressed by the MOVX instruction. The value of the data byte written does not matter. 0: Flash program memory erasure disabled. 1: Flash program memory erasure enabled. 0 PSWE Program Store Write Enable Setting this bit allows writing a byte of data to the Flash program memory using the MOVX write instruction. The Flash location should be erased before writing data. 0: Writes to Flash program memory disabled. 1: Writes to Flash program memory enabled; the MOVX write instruction targets Flash memory. Rev. 1.2 137

C8051F39x/37x SFR Definition 21.2. FLKEY: Flash Lock and Key Bit 7 6 5 4 3 2 1 0 Name FLKEY[7:0] Type R/W Reset 0 0 0 0 0 0 0 0 SFR Address=0xB7; SFR Page=All Pages Bit Name Function 7:0 FLKEY[7:0] Flash Lock and Key Register. Write: This register provides a lock and key function for Flash erasures and writes. Flash writes and erases are enabled by writing 0xA5 followed by 0xF1 to the FLKEY register. Flash writes and erases are automatically disabled after the next write or erase is com- plete. If any writes to FLKEY are performed incorrectly, or if a Flash write or erase operation is attempted while these opera- tions are disabled, the Flash will be permanently locked from writes or erasures until the next device reset. If an application never writes to Flash, it can intentionally lock the Flash by writing a non-0xA5 value to FLKEY from software. Read: When read, bits 1–0 indicate the current Flash lock state. 00: Flash is write/erase locked. 01: The first key code has been written (0xA5). 10: Flash is unlocked (writes/erases allowed). 11: Flash writes/erases disabled until the next reset. 138 Rev. 1.2

C8051F39x/37x SFR Definition 21.3. FLSCL: Flash Scale Bit 7 6 5 4 3 2 1 0 Name FOSE FLRT Type R/W R/W R/W R/W R/W R/W R/W R/W Reset 1 0 0 0 0 0 0 0 SFR Address=0xB6; SFR Page=All Pages Bit Name Function 7 FOSE Flash One-shot Enable This bit enables the Flash read one-shot (recommended). If the Flash one-shot is disabled, the Flash sense amps are enabled for a full clock cycle during Flash reads, increasing the device power consumption. 0: Flash one-shot disabled. 1: Flash one-shot enabled. 6:5 Reserved Must Write 00b. 4 FLRT Flash Read Timing This bit should be programmed to the smallest allowed value, according to the system clock speed. 0: SYSCLK < 25MHz. 1: SYSCLK < 50MHz. 3:0 Reserved Must Write 0000b. Rev. 1.2 139

C8051F39x/37x 22. EEPROM (C8051F37x) The C8051F37x devices contain 512 bytes of byte-programmable EEPROM. The EEPROM is accessible by a 2-wire bus, available on EESDA and EESCL pins, which correspond to P2.2 and P2.3 respectively. The EEPROM operates as a slave. The master can be either the SMBUS1 peripheral of the C8051F37x, internally connected to EESDA and EESCL, or an external master connected externally to the EESDA and EESCL pins. 22.1. EEPROM Communication Protocol Communication between the master and the EEPROM consists of two types of operations: writes and reads. An overview of both operations is as follows:  The master generates the clock on EESCL.  Communication begins when the master generates a START condition by causing a falling edge in EESDA when EESCL is logic high.  The master sends the slave address byte. See Section 22.1.1.  The EEPROM acknowledges the receipt of the slave address byte generating an ACK. See Section 22.1.2.  The master performs a read or write operation based on the setting of the R/W bit in the slave address byte. See Section 22.2 and Section 22.3.  Throughout communication, the state of EESDA represents one bit of valid data when EESCL is logic high: The master is permitted to change the state of EESDA when EESCL is logic high only to generate a START or STOP condition. Any changes in the EESDA line while the EESCL line is logic high will be interpreted as a START or STOP condition by the EEPROM. The master or EEPROM is permitted to change the state of EESDA when EESCL is logic low.  Communication terminates when the master generates a STOP condition by causing a rising edge in EESDA when EESCL is logic high.  If necessary, the master can reset the communication with the EEPROM. See Section 22.1.4. 140 Rev. 1.2

C8051F39x/37x 22.1.1. Slave Address Byte The master begins a transmission by sending a START condition followed by the slave address byte (SAB). Slave Address Byte (SAB) Definition Bit 7 6 5 4 3 2 1 0 Name SLA ADDR MSB R/W Value 1 0 1 0 0 0 Varies Varies Bit Name Function 7:2 SLA Slave Address of EEPROM. Always 101000b. 1 ADDR MSB Most Significant Addressing Bit. This bit is concatenated to the 8-bit address counter to create a 9-bit address used by EEPROM read and write operations. 0: Address locations 0x000 to 0x0FF are targeted by the EEPROM operations. 1: Address locations 0x100 to 0x1FF are targeted by the EEPROM operations. 0 R/W EEPROM Read/Write Direction Bit. Instructs the EEPROM to perform a read or write operation 0: Perform an EEPROM write operation 1: Perform an EEPROM read operation Figure 22.1. Slave Address Byte Definition 22.1.2. Acknowledgement (ACK) During an acknowledgement (ACK), the master or EEPROM forces the EESDA line to a logic low when EESCL is logic high. 22.1.3. Not-Acknowledgement (NACK) During a not-acknowledgement (NACK), the master or EEPROM allows the EESDA line to be pulled up to a logic high when EESCL is logic high. 22.1.4. Reset The EEPROM can be reset in case the SMBus communication is accidentally interrupted (e.g. power loss) or needs to be terminated mid-stream. The reset is initialized when the master device creates a START condition. To do this, it may be necessary for the master device to monitor EESDA up to nine times while cycling the EESCL signal. During this process, the master checks for a logic high on EESDA for each rising edge of EESCL. Rev. 1.2 141

C8051F39x/37x 22.2. Write Operation Up to sixteen successive bytes may be written to the EEPROM within a single write operation. These writes are in 16-byte pages and must be page aligned. To write to the EEPROM: 1. The master sends the START condition and the slave address byte with the R/W bit cleared to 0. 2. The EEPROM generates an ACK. 3. The master sends the write address location (A[7:0]) to the EEPROM. 4. The EEPROM stores the address location in its address counter and generates an ACK. 5. The master transmits the data byte (D[7:0]) to the EEPROM. 6. The EEPROM increments four least significant bits of the address counter by 1 and generates an ACK. The four most significant bits of the address counter are unchanged. 7. The master can repeat Steps 5 and 6 up to fifteen more times. 8. The master generates a STOP condition. 9. The EEPROM begins its internal programming cycle. 10.The master transmits a START condition and slave address with the R/W bit cleared to 0: a. If the EEPROM does not generate an ACK, repeat Steps 8 and 9. b. If the EEPROM does generate and ACK, the EEPROM internal programming cycle is complete. Note: The write address sets the upper 4 bits of the EEPROM write address pointer, and this value does not change. The lower four bits increment by 1. Because of this, the write cannot occur across 16-byte page boundaries in the same I2C write operation. Master Slave Master Slave Master Slave Master EESCL EESDA SLA[5:0] A[8] W Address Data Byte START Slave Address Byte ACK Byte ACK (D[7:0]) ACK STOP (SAB[7:0]) (A[7:0]) Figure 22.2. Write Operation (Single Byte) Master Slave Master Slave Master Slave Master Slave Master Slave Master Slave Master EESCL EESDA START (SAASdBBdlayr[vt7eee:s0 s] ) ACK A(AdB[dy7rt:ee0s])s ACK D(aDt[a7n B:0y]t)e ACK D(aDnt[a 7+ B: 01y]t)e ACK D(aDnt[a 7+ B: 02y]t)e ACK Dm(anDt [a<+7 B2:m05y],5t)e ACK STOP Figure 22.3. Write Operation (Multiple Bytes) 142 Rev. 1.2

C8051F39x/37x 22.3. Read Operation There are two operations to read the EEPROM: current address read and selective address read. Both read operations can read up to 256 bytes within a single read operation. 22.3.1. Current Address Read A current address read accesses the data at the EEPROM internal address counter’s current location. The address counter in the EEPROM maintains the address of the last byte accessed, incremented by one. For example, if the previous operation was a read or write operation addressed to address location n, the internal address counter automatically increments to address n+1. To perform a current address read operation: 1. The master sends the START condition and the slave address byte with the R/W bit set to 1. 2. The EEPROM generates an ACK and transmits the byte of data (D[7:0]) stored at the address specified by the address counter. This address will be the address from the last read or write operation incremented by one. 3. The EEPROM increments the internal address counter by one. 4. (Optional) To read additional bytes: a. The master generates an ACK. b. The EEPROM transmits the byte of data stored at the address specified by the address counter. c. The EEPROM increments the internal address counter by one. d. Repeat Step 4a through 4c until the master is done reading bytes. 5. The master generates a NACK. 6. The master generates a STOP condition. 7. The EEPROM terminates the transmission. Note: If the previous operation targeted the last byte of the EEPROM, the EEPROM will transmit the data from address location 0x00 for a current address read operation. Master Slave Master EESCL EESDA SLA[5:0] A[8] R Data Byte START Slave Address Byte ACK (D[7:0]) NACK STOP (SAB[7:0]) Figure 22.4. Current Address Read Operation (Single Byte) Rev. 1.2 143

C8051F39x/37x Master Slave Master Slave Master Slave Master EESCL EESDA Slave Data Byte Data Byte Data Byte Address n + m, START ACK n ACK n + 1 ACK NACK STOP Byte m < 255 (D[7:0]) (D[7:0]) (SAB[7:0]) (D[7:0]) Figure 22.5. Current Address Read Operation (Multiple Bytes) 144 Rev. 1.2

C8051F39x/37x 22.3.2. Selective Address Read In a selective address read operation, the master selects the target memory location for the read operation. To perform a selective address read: 1. The master sends the START condition and the slave address byte with the R/W bit set to 1. 2. The EEPROM generates an ACK. 3. The master sends the read memory address (A[7:0]) to the EEPROM. 4. The EEPROM stores the address in the address counter and generates an ACK. 5. The master again sends the slave address byte with the R/W bit set to 1. 6. The EEPROM generates an ACK. 7. The EEPROM sends the byte of data (D[7:0]) specified by the address counter. 8. The EEPROM increments the internal address counter by one. 9. (Optional) To read additional bytes: a. The master generates an ACK. b. The EEPROM sends the byte of data (D[7:0]) specified by the address counter. c. The EEPROM increments the internal address counter by one. d. Repeat Steps9a through 9c until the master reads all of the desired bytes. 10.The master generates a NACK. 11.The master generates a STOP condition. 12.The EEPROM terminates the transmission. Note: If the selective read operation overflows the top of memory, the EEPROM address counter will wrap, and the EEPROM transmit the data from address location 0x00. Master Slave Master Slave Master Slave Master EESCL EESDA Slave Slave Address Address Address Data Byte START ACK Byte ACK ACK NACK STOP Byte Byte (D[7:0]) (A[7:0]) (SAB[7:0]) (SAB[7:0]) Figure 22.6. Selective Address Read (Single Byte) Rev. 1.2 145

C8051F39x/37x Master Slave Master Slave Master Slave Master Slave Master Slave Master EESCL EESDA START (SAASdBBdlayr[vt7eees:0 s] ) ACK A(AdB[d7yr:te0es])s ACK (SAASdBBdlayr[vt7eee:s0 s] ) ACK D(aDta[7n B:0y]t)e ACK D(aDnta[ 7+ B: 01y]t)e ACK Dm(anDt a[<+7 B2:m05y],5t)e NACK STOP Figure 22.7. Selective Address Read (Multiple Bytes) 146 Rev. 1.2

C8051F39x/37x 23. Cyclic Redundancy Check Unit (CRC0) C8051F39x/37x devices include a cyclic redundancy check unit (CRC0) that can perform a CRC using a 16-bit polynomial. CRC0 accepts a stream of 8-bit data written to the CRC0IN register. CRC0 posts the 16- bit result to an internal register. The internal result register may be accessed indirectly using the CRC0PNT bits and CRC0DAT register, as shown in Figure23.1. CRC0 also has a bit reverse register for quick data manipulation. 8 8 Automatic CRC Flash CRC0IN Controller Memory AUTOEN N C 0 CRC0ST[5] O RC CRC0INIT CRC Engine CRC0ST[4] UT C CRC0VAL CRC0ST[3] 0A C CRC0ST[2] R C CRC0PNT CRC0ST[1] 16 CRC0ST[0] CRC0DONE CRC0FLIP RESULT CRC0CNT[5] T Write N CRC0CNT[4] C 0 CRC0CNT[3] C R CRC0CNT[2] C 8 8 CRC0CNT[1] CRC0CNT[0] 2 to 1 MUX CRC0FLIP Read 8 CRC0DAT Figure 23.1. CRC0 Block Diagram 23.1. CRC Algorithm The C8051F39x/37x CRC unit generates a CRC result equivalent to the following algorithm: 1. XOR the input with the most-significant bits of the current CRC result. If this is the first iteration of the CRC unit, the current CRC result will be the set initial value (0x00000000 or 0xFFFFFFFF). 2a. If the MSB of the CRC result is set, shift the CRC result and XOR the result with the selected polynomial. 2b. If the MSB of the CRC result is not set, shift the CRC result. Repeat Steps 2a/2b for the number of input bits (8). The algorithm is also described in the following exam- ple. Rev. 1.2 147

C8051F39x/37x The 16-bit C8051F39x/37x CRC algorithm can be described by the following code: unsigned short UpdateCRC (unsigned short CRC_acc, unsigned char CRC_input) { unsigned char i; // loop counter #define POLY 0x1021 // Create the CRC "dividend" for polynomial arithmetic (binary arithmetic // with no carries) CRC_acc = CRC_acc ^ (CRC_input << 8); // "Divide" the poly into the dividend using CRC XOR subtraction // CRC_acc holds the "remainder" of each divide // // Only complete this division for 8 bits since input is 1 byte for (i = 0; i < 8; i++) { // Check if the MSB is set (if MSB is 1, then the POLY can "divide" // into the "dividend") if ((CRC_acc & 0x8000) == 0x8000) { // if so, shift the CRC value, and XOR "subtract" the poly CRC_acc = CRC_acc << 1; CRC_acc ^= POLY; } else { // if not, just shift the CRC value CRC_acc = CRC_acc << 1; } } // Return the final remainder (CRC value) return CRC_acc; } Table23.1 lists several input values and the associated outputs using the 16-bit C8051F39x/37x CRC algorithm: Table 23.1. Example 16-bit CRC Outputs Input Output 0x63 0xBD35 0x8C 0xB1F4 0x7D 0x4ECA 0xAA, 0xBB, 0xCC 0x6CF6 0x00, 0x00, 0xAA, 0xBB, 0xCC 0xB166 148 Rev. 1.2

C8051F39x/37x 23.2. Preparing for a CRC Calculation To prepare CRC0 for a CRC calculation, software should set the initial value of the result. The polynomial used for the CRC computation is 0x1021. The CRC0 result may be initialized to one of two values: 0x0000 or 0xFFFF. The following steps can be used to initialize CRC0. 1. Select the initial result value (Set CRC0VAL to 0 for 0x0000 or 1 for 0xFFFF). 2. Set the result to its initial value (Write 1 to CRC0INIT). 23.3. Performing a CRC Calculation Once CRC0 is initialized, the input data stream is sequentially written to CRC0IN, one byte at a time. The CRC0 result is automatically updated after each byte is written. The CRC engine may also be configured to automatically perform a CRC on one or more 256 byte blocks read from Flash. The following steps can be used to automatically perform a CRC on Flash memory. 1. Prepare CRC0 for a CRC calculation as shown above. 2. Write the index of the starting page to CRC0AUTO. 3. Set the AUTOEN bit to 1 in CRC0AUTO. 4. Write the number of 256 byte blocks to perform in the CRC calculation to CRC0CNT. 5. Write any value to CRC0CN (or OR its contents with 0x00) to initiate the CRC calculation. The CPU will not execute code any additional code until the CRC operation completes. See the note in SFR Definition23.1.CRC0CN: CRC0 Control for more information on how to properly initiate a CRC calculation. 6. Clear the AUTOEN bit in CRC0AUTO. 7. Read the CRC result using the procedure below. 23.4. Accessing the CRC0 Result The internal CRC0 result is 16 bits. The CRC0PNT bits select the byte that is targeted by read and write operations on CRC0DAT and increment after each read or write. The calculation result will remain in the internal CR0 result register until it is set, overwritten, or additional data is written to CRC0IN. 23.5. CRC0 Bit Reverse Feature CRC0 includes hardware to reverse the bit order of each bit in a byte as shown in Figure23.2. Each byte of data written to CRC0FLIP is read back bit reversed. For example, if 0xC0 is written to CRC0FLIP, the data read back is 0x03. Bit reversal is a useful mathematical function used in algorithms such as the FFT. CRC0FLIP Write CRC0FLIP Read Figure 23.2. Bit Reverse Register Rev. 1.2 149

C8051F39x/37x SFR Definition 23.1. CRC0CN: CRC0 Control Bit 7 6 5 4 3 2 1 0 Name CRC0INIT CRC0VAL CRC0PNT Type R R R R R/W R/W R R/W Reset 0 0 0 1 0 0 0 0 SFR Address=0xDF; SFR Page=All Pages Bit Name Function 7:4 Unused Read=0001b; Write=Don’t Care. 3 CRC0INIT CRC0 Result Initialization Bit. Writing a 1 to this bit initializes the entire CRC result based on CRC0VAL. 2 CRC0VAL CRC0 Set Value Initialization Bit. This bit selects the set value of the CRC result. 0: CRC result is set to 0x00000000 on write of 1 to CRC0INIT. 1: CRC result is set to 0xFFFFFFFF on write of 1 to CRC0INIT. 1 Unused Read=0b; Write=Don’t Care. 0 CRC0PNT CRC0 Result Pointer. Specifies the byte of the CRC result to be read/written on the next access to CRC0DAT. The value of these bits will auto-increment upon each read or write. 0: CRC0DAT accesses bits 7–0 of the 16-bit CRC result. 1: CRC0DAT accesses bits 15–8 of the 16-bit CRC result. Note: Upon initiation of an automatic CRC calculation, the three cycles following a write to CRC0CN that initiate a CRC operation must only contain instructions which execute in the same number of cycles as the number of bytes in the instruction. An example of such an instruction is a 3-byte MOV that targets the CRC0FLIP register. When programming in C, the dummy value written to CRC0FLIP should be a non-zero value to prevent the compiler from generating a 2-byte MOV instruction. 150 Rev. 1.2

C8051F39x/37x SFR Definition 23.2. CRC0IN: CRC0 Data Input Bit 7 6 5 4 3 2 1 0 Name CRC0IN[7:0] Type R/W Reset 0 0 0 0 0 0 0 0 SFR Address=0x9C; SFR Page=All Pages Bit Name Function 7:0 CRC0IN[7:0] CRC0 Data Input. Each write to CRC0IN results in the written data being com- puted into the existing CRC result according to the CRC algorithm described in Section 23.1 SFR Definition 23.3. CRC0DAT: CRC0 Data Output Bit 7 6 5 4 3 2 1 0 Name CRC0DAT[7:0] Type R/W Reset 0 0 0 0 0 0 0 0 SFR Address=0x9E; SFR Page=All Pages Bit Name Function 7:0 CRC0DAT[7:0] CRC0 Data Output. Each read or write performed on CRC0DAT targets the CRC result bits pointed to by the CRC0 Result Pointer (CRC0PNT bits in CRC0CN). Rev. 1.2 151

C8051F39x/37x SFR Definition 23.4. CRC0AUTO: CRC0 Automatic Control Bit 7 6 5 4 3 2 1 0 Name AUTOEN CRC0ST[5:0] Type R/W R/W R/W Reset 0 0 0 0 0 0 0 0 SFR Address=0xDD; SFR Page=All Pages Bit Name Function 7 AUTOEN Automatic CRC Calculation Enable. When AUTOEN is set to 1, any write to CRC0CN will initi- ate an automatic CRC starting at Flash sector CRC0ST and continuing for CRC0CNT sectors. 6 Reserved Must write 0b. 5:0 CRC0ST[5:0] Automatic CRC Calculation Starting Block. These bits specify the Flash block to start the automatic CRC calculation. The starting address of the first Flash block included in the automatic CRC calculation is CRC0ST x Block Size. Note: The block size is 256 bytes. 152 Rev. 1.2

C8051F39x/37x SFR Definition 23.5. CRC0CNT: CRC0 Automatic Flash Sector Count Bit 7 6 5 4 3 2 1 0 Name CRCDONE CRC0CNT[5:0] Type R R/W R/W Reset 1 0 0 0 0 0 0 0 SFR Address=0xDE; SFR Page=All Pages Bit Name Function 7 CRCDONE CRCDONE Automatic CRC Calculation Complete. Set to 0 when a CRC calculation is in progress. Code exe- cution is stopped during a CRC calculation; therefore, reads from firmware will always return 1. 6 Reserved Must write 0b. 5:0 CRC0CNT[5:0] Automatic CRC Calculation Block Count. These bits specify the number of Flash blocks to include in an automatic CRC calculation. The last address of the last Flash block included in the automatic CRC calculation is (CRC0ST+CRC0CNT) x Block Size - 1. Notes: 1. The block size is 256 bytes. Rev. 1.2 153

C8051F39x/37x SFR Definition 23.6. CRC0FLIP: CRC0 Bit Flip Bit 7 6 5 4 3 2 1 0 Name CRC0FLIP[7:0] Type R/W Reset 0 0 0 0 0 0 0 0 SFR Address=0x9A; SFR Page=All Pages Bit Name Function 7:0 CRC0FLIP[7:0] CRC0 Bit Flip. Any byte written to CRC0FLIP is read back in a bit- reversed order, i.e., the written LSB becomes the MSB. For example: If 0xC0 is written to CRC0FLIP, the data read back will be 0x03. If 0x05 is written to CRC0FLIP, the data read back will be 0xA0. 154 Rev. 1.2

C8051F39x/37x 24. Reset Sources Reset circuitry allows the controller to be easily placed in a predefined default condition. Upon entering this reset state, the following events occur:  CIP-51 halts program execution  Special Function Registers (SFRs) are initialized to their defined reset values  External Port pins are forced to a known state  Interrupts and timers are disabled. All SFRs are reset to the predefined values noted in the SFR detailed descriptions. The contents of internal data memory are unaffected during a reset; any previously stored data is preserved. However, since the stack pointer SFR is reset, the stack is effectively lost, even though the data on the stack is not altered. The Port I/O latches are reset to 0xFF (all logic ones) in open-drain mode. Weak pullups are enabled during and after the reset. For V Monitor and power-on resets, the RST pin is driven low until the device DD exits the reset state. On exit from the reset state, the program counter (PC) is reset, and the system clock defaults to the inter- nal oscillator. The Watchdog Timer is enabled with the system clock divided by 12 as its clock source. Pro- gram execution begins at location 0x0000. VDD Power On Reset Supply Monitor + '0' /RST Comparator 0 - Enable (wired-OR) Px.x + - Px.x C0RSEF Missing Reset Clock Detector Funnel (one- shot) PCA WDT (Software Reset) EN SWRSF EN Errant MCD nable WDT nable OFpLeAraStiHo n E E System Clock CIP-51 Microcontroller System Reset Core Extended Interrupt Handler Figure 24.1. Reset Sources Rev. 1.2 155

C8051F39x/37x 24.1. Power-On Reset During power-up, the device is held in a reset state and the RST pin is driven low until V settles above DD V . A delay occurs before the device is released from reset; the delay decreases as the V ramp time RST DD increases (V ramp time is defined as how fast V ramps from 0V to V ). Figure24.2. plots the DD DD RST power-on and V monitor reset timing. For ramp times less than 1ms, the power-on reset delay (T DD PORDe- ) is typically less than 0.3ms. lay On exit from a power-on reset, the PORSF flag (RSTSRC.1) is set by hardware to logic1. When PORSF is set, all of the other reset flags in the RSTSRC Register are indeterminate (PORSF is cleared by all other resets). Since all resets cause program execution to begin at the same location (0x0000) software can read the PORSF flag to determine if a power-up was the cause of reset. The content of internal data mem- ory should be assumed to be undefined after a power-on reset. The V monitor is enabled following a DD power-on reset. s volt VDD 1.8 VRST 1.7 D D V 1.0 t /RST Logic HIGH T PORDelay Logic LOW VDD Power-On Monitor Reset Reset Figure 24.2. Power-On and V Monitor Reset Timing DD 156 Rev. 1.2

C8051F39x/37x 24.2. Power-Fail Reset / V Monitor DD When a power-down transition or power irregularity causes V to drop below V , the power supply DD RST monitor will drive the RST pin low and hold the CIP-51 in a reset state (see Figure24.2). When V returns DD to a level above V , the CIP-51 will be released from the reset state. Note that even though internal data RST memory contents are not altered by the power-fail reset, it is impossible to determine if V dropped below DD the level required for data retention. If the PORSF flag reads ‘1’, the data may no longer be valid. The V DD monitor is enabled after power-on resets. Its defined state (enabled/disabled) is not altered by any other reset source. For example, if the V monitor is disabled by code and a software reset is performed, the DD V monitor will still be disabled after the reset. DD Important Note: If the V monitor is being turned on from a disabled state, it should be enabled before it DD is selected as a reset source. Selecting the V monitor as a reset source before it is enabled and stabi- DD lized may cause a system reset. In some applications, this reset may be undesirable. If this is not desirable in the application, a delay should be introduced between enabling the monitor and selecting it as a reset source. The procedure for enabling the V monitor and configuring it as a reset source from a disabled DD state is shown below: 1. Enable the V monitor (VDMEN bit in VDM0CN=‘1’). DD 2. If necessary, wait for the V monitor to stabilize. DD 3. Select the V monitor as a reset source (PORSF bit in RSTSRC=‘1’). DD See Figure24.2 for V monitor timing; note that the power-on-reset delay is not incurred after a V DD DD monitor reset. See Section “7.Electrical Characteristics” on page32 for complete electrical characteristics of the V monitor. DD Rev. 1.2 157

C8051F39x/37x SFR Definition 24.1. VDM0CN: V Monitor Control DD Bit 7 6 5 4 3 2 1 0 Name VDMEN VDDSTAT VDMLVL Type R/W R R/W R R R R R Reset Varies Varies 0 0 0 0 0 0 SFR Address=0xFF; SFR Page=All Pages Bit Name Function 7 VDMEN V Monitor Enable. DD This bit turns the V monitor circuit on/off. The V Monitor DD DD cannot generate system resets until it is also selected as a reset source in register RSTSRC (SFR Definition 24.2). Selecting the V monitor as a reset source before it has DD stabilized may generate a system reset. In systems where this reset would be undesirable, a delay should be intro- duced between enabling the V Monitor and selecting it as DD a reset source. 0: V Monitor Disabled. DD 1: V Monitor Enabled. DD 6 VDDSTAT V Status. DD This bit indicates the current power supply status (V Mon- DD itor output). 0: V is at or below the V monitor threshold. DD DD 1: V is above the V monitor threshold. DD DD 5 VDMLVL VDD Monitor Level Select. 0: VDD Monitor Threshold is set to VRST-LOW. 1: VDD Monitor Threshold is set to VRST-HIGH. This setting is required for any system with firmware that writes and/or erases Flash. 4:0 Unused Read=000000b; Write=Don’t care. 158 Rev. 1.2

C8051F39x/37x 24.3. External Reset The external RST pin provides a means for external circuitry to force the device into a reset state. Assert- ing an active-low signal on the RST pin generates a reset; an external pullup and/or decoupling of the RST pin may be necessary to avoid erroneous noise-induced resets. See Section “7.Electrical Characteristics” on page32 for complete RST pin specifications. The PINRSF flag (RSTSRC.0) is set on exit from an exter- nal reset. 24.4. Missing Clock Detector Reset The Missing Clock Detector (MCD) is a one-shot circuit that is triggered by the system clock. If the system clock remains high or low for more than 100µs, the one-shot will time out and generate a reset. After a MCD reset, the MCDRSF flag (RSTSRC.2) will read ‘1’, signifying the MCD as the reset source; otherwise, this bit reads ‘0’. Writing a ‘1’ to the MCDRSF bit enables the Missing Clock Detector; writing a ‘0’ disables it. The state of the RST pin is unaffected by this reset. 24.5. Comparator0 Reset Comparator0 can be configured as a reset source by writing a ‘1’ to the C0RSEF flag (RSTSRC.5). Com- parator0 should be enabled and allowed to settle prior to writing to C0RSEF to prevent any turn-on chatter on the output from generating an unwanted reset. The Comparator0 reset is active-low: if the non-inverting input voltage (on CP0+) is less than the inverting input voltage (on CP0-), the device is put into the reset state. After a Comparator0 reset, the C0RSEF flag (RSTSRC.5) will read ‘1’ signifying Comparator0 as the reset source; otherwise, this bit reads ‘0’. The state of the RST pin is unaffected by this reset. 24.6. PCA Watchdog Timer Reset The programmable Watchdog Timer (WDT) function of the Programmable Counter Array (PCA) can be used to prevent software from running out of control during a system malfunction. The PCA WDT function can be enabled or disabled by software as described in Section “32.4.Watchdog Timer Mode” on page286; the WDT is enabled and clocked by SYSCLK/12 following any reset. If a system malfunction prevents user software from updating the WDT, a reset is generated and the WDTRSF bit (RSTSRC.5) is set to ‘1’. The state of the RST pin is unaffected by this reset. 24.7. Flash Error Reset If a Flash read/write/erase or program read targets an illegal address, a system reset is generated. This may occur due to any of the following:  A Flash write or erase is attempted above user code space. This occurs when PSWE is set to ‘1’ and a MOVX write operation targets an address above address 0x3DFF.  A Flash read is attempted above user code space. This occurs when a MOVC operation targets an address above address 0x3DFF.  A Program read is attempted above user code space. This occurs when user code attempts to branch to an address above 0x3DFF.  A Flash read, write or erase attempt is restricted due to a Flash security setting (see Section “21.3.Security Options” on page133). The FERROR bit (RSTSRC.6) is set following a Flash error reset. The state of the RST pin is unaffected by this reset. 24.8. Software Reset Software may force a reset by writing a ‘1’ to the SWRSF bit (RSTSRC.4). The SWRSF bit will read ‘1’ fol- lowing a software forced reset. The state of the RST pin is unaffected by this reset. Rev. 1.2 159

C8051F39x/37x SFR Definition 24.2. RSTSRC: Reset Source Bit 7 6 5 4 3 2 1 0 Name FERROR C0RSEF SWRSF WDTRSF MCDRSF PORSF PINRSF Type R R R/W R/W R R/W R/W R Reset 0 Varies Varies Varies Varies Varies Varies Varies SFR Address=0xEF; SFR Page=All Pages Bit Name Description Write Read 7 Unused Unused. Don’t care. 0 6 FERROR Flash Error Reset Flag. N/A Set to ‘1’ if Flash read/ write/erase error caused the last reset. 5 C0RSEF Comparator0 Reset Enable Writing a ‘1’ enables Com- Set to ‘1’ if Comparator0 and Flag. parator0 as a reset source caused the last reset. (active-low). 4 SWRSF Software Reset Force and Writing a ‘1’ forces a sys- Set to ‘1’ if last reset was Flag. tem reset. caused by a write to SWRSF. 3 WDTRSF Watchdog Timer Reset Flag. N/A Set to ‘1’ if Watchdog Timer overflow caused the last reset. 2 MCDRSF Missing Clock Detector Writing a ‘1’ enables the Set to ‘1’ if Missing Clock Enable and Flag. Missing Clock Detector. Detector timeout caused The MCD triggers a reset the last reset. if a missing clock condition is detected. 1 PORSF Power-On / V Monitor Writing a ‘1’ enables the Set to ‘1’ anytime a power- DD V monitor as a reset on or V monitor reset Reset Flag, and V monitor DD DD DD source. occurs. Reset Enable. Writing ‘1’ to this bit When set to ‘1’ all other before the V monitor RSTSRC flags are inde- DD is enabled and stabilized terminate. may cause a system reset. 0 PINRSF HW Pin Reset Flag. N/A Set to ‘1’ if RST pin caused the last reset. Note: Do not use read-modify-write operations on this register 160 Rev. 1.2

C8051F39x/37x 25. Power Management Modes The C8051F39x/37x devices have three software programmable power management modes: idle, stop, and Suspend. Idle mode and stop mode are part of the standard 8051 architecture, while suspend mode is an enhanced power-saving mode implemented by the high-speed oscillator. Idle mode halts the CPU while leaving the peripherals and clocks active. In stop mode, the CPU is halted, all interrupts and timers (except the Missing Clock Detector) are inactive, and the internal oscillator is stopped (analog peripherals remain in their selected states; the external oscillator is not affected). Sus- pend mode is similar to Stop mode in that the internal oscillator and CPU are halted, but the device can wake on events such as a Port Mismatch, Comparator low output, or a Timer3 overflow. Since clocks are running in Idle mode, power consumption is dependent upon the system clock frequency and the number of peripherals left in active mode before entering Idle. Stop mode and suspend mode consume the least power because the majority of the device is shut down with no clocks active. SFR Definition 25.1 describes the Power Control Register (PCON) used to control the C8051F39x/37x's Stop and Idle power manage- ment modes. Suspend mode is controlled by the SUSPEND bit in the OSCICN register (SFR Definition 26.3). Although the C8051F39x/37x has idle, stop, and suspend modes available, more control over the device power can be achieved by enabling/disabling individual peripherals as needed. Each analog peripheral can be disabled when not in use and placed in low power mode. Digital peripherals, such as timers or serial buses, draw little power when they are not in use. Turning off oscillators lowers power consumption considerably, at the expense of reduced functionality. 25.1. Idle Mode Setting the Idle Mode Select bit (PCON.0) causes the hardware to halt the CPU and enter idle mode as soon as the instruction that sets the bit completes execution. All internal registers and memory maintain their original data. All analog and digital peripherals can remain active during idle mode. Idle mode is terminated when an enabled interrupt is asserted or a reset occurs. The assertion of an enabled interrupt will cause the Idle Mode Selection bit (PCON.0) to be cleared and the CPU to resume operation. The pending interrupt will be serviced and the next instruction to be executed after the return from interrupt (RETI) will be the instruction immediately following the one that set the Idle Mode Select bit. If idle mode is terminated by an internal or external reset, the CIP-51 performs a normal reset sequence and begins program execution at address 0x0000. Note: If the instruction following the write of the IDLE bit is a single-byte instruction and an interrupt occurs during the execution phase of the instruction that sets the IDLE bit, the CPU may not wake from Idle mode when a future interrupt occurs. Therefore, instructions that set the IDLE bit should be followed by an instruction that has two or more opcode bytes, for example: // in ‘C’: PCON |= 0x01; // set IDLE bit PCON = PCON; // ... followed by a 3-cycle dummy instruction ; in assembly: ORL PCON, #01h ; set IDLE bit MOV PCON, PCON ; ... followed by a 3-cycle dummy instruction If enabled, the Watchdog Timer (WDT) will eventually cause an internal watchdog reset and thereby termi- nate the idle mode. This feature protects the system from an unintended permanent shutdown in the event of an inadvertent write to the PCON register. If this behavior is not desired, the WDT may be disabled by software prior to entering the Idle mode if the WDT was initially configured to allow this operation. This pro- vides the opportunity for additional power savings, allowing the system to remain in the Idle mode indefi- nitely, waiting for an external stimulus to wake up the system. Refer to Section “24.6.PCA Watchdog Timer Reset” on page159 for more information on the use and configuration of the WDT. Rev. 1.2 161

C8051F39x/37x 25.2. Stop Mode Setting the Stop Mode Select bit (PCON.1) causes the controller core to enter Stop mode as soon as the instruction that sets the bit completes execution. Before entering stop mode, the system clock must be sourced by the internal high-frequency oscillator. In stop mode the internal oscillator, CPU, and all digital peripherals are stopped; the state of the external oscillator circuit is not affected. Each analog peripheral (including the external oscillator circuit) may be shut down individually prior to entering stop mode. Stop mode can only be terminated by an internal or external reset. On reset, the device performs the normal reset sequence and begins program execution at address 0x0000. If enabled, the Missing Clock Detector will cause an internal reset and thereby terminate the stop mode. The Missing Clock Detector should be disabled if the CPU is to be put to in STOP mode for longer than the MCD timeout. By default, when in stop mode the internal regulator is still active. However, the regulator can be config- ured to shut down while in stop mode to save power. To shut down the regulator in stop mode, the STOPCF bit in register REG01CN should be set to 1 prior to setting the STOP bit (see SFR Definition 25.1). If the regulator is shut down using the STOPCF bit, only the RST pin or a full power cycle are capa- ble of resetting the device. 25.3. Suspend Mode Setting the SUSPEND bit (OSCICN.5) causes the hardware to halt the CPU and the high-frequency inter- nal oscillator, and go into suspend mode as soon as the instruction that sets the bit completes execution. All internal registers and memory maintain their original data. Most digital peripherals are not active in sus- pend mode. The exception to this is the Port Match feature and Timer3, when it is run from an external oscillator source or the internal low-frequency oscillator. Suspend mode can be terminated by four types of events, a port match (described in Section “27.5.Port Match” on page183), a Timer3 overflow (described in Section “31.3.Timer 3” on page259), a Comparator low output (if enabled), or a device reset event. Note that in order to run Timer3 in suspend mode, the timer must be configured to clock from either the external clock source or the internal low-frequency oscil- lator source. When suspend mode is terminated, the device will continue execution on the instruction fol- lowing the one that set the SUSPEND bit. If the wake event (port match or Timer3 overflow) was configured to generate an interrupt, the interrupt will be serviced upon waking the device. If suspend mode is terminated by an internal or external reset, the CIP-51 performs a normal reset sequence and begins program execution at address 0x0000. 162 Rev. 1.2

C8051F39x/37x SFR Definition 25.1. PCON: Power Control Bit 7 6 5 4 3 2 1 0 Name GF[5:0] STOP IDLE Type R/W R/W R/W Reset 0 0 0 0 0 0 0 0 SFR Address=0x87; SFR Page=All Pages Bit Name Function 7:2 GF[5:0] General Purpose Flags 5–0. These are general purpose flags for use under software control. 1 STOP Stop Mode Select. Setting this bit will place the CIP-51 in Stop mode. This bit will always be read as 0. 1: CPU goes into Stop mode (internal oscillator stopped). 0 IDLE IDLE: Idle Mode Select. Setting this bit will place the CIP-51 in Idle mode. This bit will always be read as 0. 1: CPU goes into Idle mode. (Shuts off clock to CPU, but clock to Timers, Interrupts, Serial Ports, and Analog Peripherals are still active.) Rev. 1.2 163

C8051F39x/37x 26. Oscillators and Clock Selection C8051F39x/37x devices include a programmable internal high-frequency oscillator, a programmable inter- nal low-frequency oscillator, an internal low-power oscillator, and an external oscillator drive circuit. The internal high-frequency oscillator can be enabled/disabled and calibrated using the OSCICN and OSCICL registers, as shown in Figure26.1. The internal low-frequency oscillator can be enabled/disabled and cali- brated using the OSCLCN register. The internal low-power oscillator is automatically enabled and disabled when selected and deselected as the system clock. The system clock can be sourced by the external oscil- lator circuit or any internal oscillator. The internal high-frequency and low-frequency oscillators offer a selectable post-scaling feature. OSCICL OSCICN OSCLCN CLKSEL IOSCENIFRDYSUSPENDSTSYNC IFCN1IFCN0 OSCLENOSCLRDYOSCLF3OSCLF2OSCLF1OSCLF0OSCLD1OSCLD0 CLKSL2CLKSL1CLKSL0 Option2 VDD Option3 OSCLENOSCLF OSCLD XTAL2 EN 49MHzHighFrequency 2,4,8,16 XTAL2 InternalOscillator (49MHz) OSCLF OSCLEN EN 80kHzLowFrequency 1,2,4,8 SYSCLK InternalOscillator Option1 OSCLD XTAL1 10M(cid:2) Input OSC Circuit XTAL2 (20MHz) Option4 20MHzLowPower XTAL2 210 InternalOscillator DDD 210 MMM NNN CCC CCC SSS FFF OOO XXX XXX OSCXCN Figure 26.1. Oscillator Options 164 Rev. 1.2

C8051F39x/37x 26.1. System Clock Selection The CLKSL[2:0] bits in register CLKSEL select which oscillator source is used as the system clock. CLKSL[2:0] must be set to 001b for the system clock to run from the external oscillator; however the exter- nal oscillator may still clock certain peripherals (timers, PCA) when the internal oscillator is selected as the system clock. The system clock may be switched on-the-fly between any of the oscillator sources so long as the selected clock source is enabled and has settled. The internal high-frequency and low-frequency oscillators require little start-up time and may be selected as the system clock immediately following the register write which enables the oscillator. The external RC and C modes also typically require no startup time. External crystals and ceramic resonators however, typically require a start-up time before they are settled and ready for use. The Crystal Valid Flag (XTLVLD in register OSCXCN) is set to '1' by hardware when the external crystal or ceramic resonator is settled. In crystal mode, to avoid reading a false XTLVLD, soft- ware should delay at least 1ms between enabling the external oscillator and checking XTLVLD. SFR Definition 26.1. CLKSEL: Clock Select Bit 7 6 5 4 3 2 1 0 Name CLKSL[2:0] Type R R R R R R/W Reset 0 0 0 0 0 0 0 0 SFR Address=0xA9; SFR Page=All Pages Bit Name Function 7:3 Unused Read=00000b; Write=Don’t Care 2:0 CLKSL[2:0] System Clock Source Select Bits. 000: SYSCLK derived from the Internal High-Frequency Oscilla- tor and scaled per the IFCN bits in register OSCICN. 001: SYSCLK derived from the External Oscillator circuit.* 010: SYSCLK derived from the Internal Low-Frequency Oscilla- tor and scaled per the OSCLD bits in register OSCLCN. 011: SYSCLK derived directly from the Internal High-Frequency Oscillator.* 100: Reserved. 101: SYSCLK derived from the Internal Low-Power Oscillator. 110: Reserved. 111: Reserved. Note: Prior to switching to a system clock frequency > 25 MHz, ensure that the FLRT bit in SFR Definition21.3.FLSCL: Flash Scale has been set appropriately to ensure proper flash read timing. Rev. 1.2 165

C8051F39x/37x 26.2. Programmable Internal High-Frequency (H-F) Oscillator All C8051F39x/37x devices include a programmable internal high-frequency oscillator that defaults as the system clock after a system reset. The internal oscillator period can be adjusted via the OSCICL register as defined by SFR Definition 26.2. On C8051F39x/37x devices, OSCICL is factory calibrated to obtain a 49MHz base frequency. The system clock may be derived directly from the programmed internal oscillator, or from a divided ver- sion, with factors of 2, 4, 8, or 16, as defined by the IFCN bits in register OSCICN. The divide value defaults to 16 following a reset. 26.2.1. Internal Oscillator Suspend Mode When software writes a logic 1 to SUSPEND (OSCICN.5), the internal oscillator is suspended. If the sys- tem clock is derived from the internal oscillator, the input clock to the peripheral or CIP-51 will be stopped until one of the following events occur:  Port 0 Match Event.  Port 1 Match Event.  Comparator0 enabled and output is logic0.  Timer3 Overflow Event. When one of the oscillator awakening events occur, the internal oscillator, CIP-51, and affected peripherals resume normal operation, regardless of whether the event also causes an interrupt. The CPU resumes execution at the instruction following the write to SUSPEND. SFR Definition 26.2. OSCICL: Internal H-F Oscillator Calibration Bit 7 6 5 4 3 2 1 0 Name OSCICL[6:0] Type R R/W Reset 0 Varies Varies Varies Varies Varies Varies Varies SFR Address=0xB3; SFR Page=All Pages Bit Name Function 7 Unused Unused. Read=0; Write=Don’t Care 6:0 OSCICL[6:0] Internal Oscillator Calibration Bits. These bits determine the internal oscillator period. When set to 0000000b, the H-F oscillator operates at its fastest setting. When set to 1111111b, the H-F oscillator operates at its slow- est setting. The reset value is factory calibrated to generate an internal oscillator frequency of 49MHz. 166 Rev. 1.2

C8051F39x/37x SFR Definition 26.3. OSCICN: Internal H-F Oscillator Control Bit 7 6 5 4 3 2 1 0 Name IOSCEN IFRDY SUSPEND STSYNC IFCN[1:0] Type R/W R R/W R R R R/W Reset 1 1 0 0 0 0 0 0 SFR Address=0xB2; SFR Page=All Pages Bit Name Function 7 IOSCEN Internal H-F Oscillator Enable Bit. 0: Internal H-F Oscillator Disabled. 1: Internal H-F Oscillator Enabled. 6 IFRDY Internal H-F Oscillator Frequency Ready Flag. 0: Internal H-F Oscillator is not running at programmed fre- quency. 1: Internal H-F Oscillator is running at programmed frequency. 5 SUSPEND Internal Oscillator Suspend Enable Bit. Setting this bit to logic 1 places the internal oscillator in SUS- PEND mode. The internal oscillator resumes operation when one of the SUSPEND mode awakening events occurs. 4 STSYNC Suspend Timer Synchronization Bit. This bit is used to indicate when it is safe to read and write the registers associated with the suspend wake-up timer. If a suspend wake-up source other than the timer has brought the oscillator out of suspend mode, it may take up to three timer clocks before the timer can be read or written. When STSYNC reads '1', reads and writes of the timer register should not be performed. When STSYNC reads '0', it is safe to read and write the timer registers. 3:2 Unused Unused. Read=00b; Write=Don’t Care 1:0 IFCN[1:0] Internal H-F Oscillator Frequency Divider Control Bits. These bits control the oscillator clock divider when the clock divider is selected as the system clock source. 00: Internal H-F divide ratio=16. 01: Internal H-F divide ratio=8. 10: Internal H-F divide ratio=4. 11: Internal H-F divide ratio=2. Rev. 1.2 167

C8051F39x/37x 26.3. Programmable Internal Low-Frequency (L-F) Oscillator All C8051F39x/37x devices include a programmable low-frequency internal oscillator, which is calibrated to a nominal frequency of 80kHz. The low-frequency oscillator circuit includes a divider that can be changed to divide the clock by 1, 2, 4, or 8, using the OSCLD bits in the OSCLCN register (see SFR Defi- nition 26.4). Additionally, the OSCLF[3:0] bits can be used to adjust the oscillator’s output frequency. 26.3.1. Calibrating the Internal L-F Oscillator Timers 2 and 3 include capture functions that can be used to capture the oscillator frequency, when run- ning from a known time base. When either Timer2 or Timer3 is configured for L-F Oscillator Capture Mode, a falling edge (Timer2) or rising edge (Timer3) of the low-frequency oscillator’s output will cause a capture event on the corresponding timer. As a capture event occurs, the current timer value (TMRnH:TMRnL) is copied into the timer reload registers (TMRnRLH:TMRnRLL). By recording the differ- ence between two successive timer capture values, the low-frequency oscillator’s period can be calcu- lated. The OSCLF bits can then be adjusted to produce the desired oscillator frequency. SFR Definition 26.4. OSCLCN: Internal L-F Oscillator Control Bit 7 6 5 4 3 2 1 0 Name OSCLEN OSCLRDY OSCLF[3:0] OSCLD[1:0] Type R/W R R.W R/W Reset 0 0 Varies Varies Varies Varies 0 0 SFR Address=0xE3; SFR Page=All Pages Bit Name Function 7 OSCLEN Internal L-F Oscillator Enable. 0: Internal L-F Oscillator Disabled. 1: Internal L-F Oscillator Enabled. 6 OSCLRDY Internal L-F Oscillator Ready. 0: Internal L-F Oscillator frequency not stabilized. 1: Internal L-F Oscillator frequency stabilized. Note: OSCLRDY is only set back to 0 in the event of a device reset or a change to the OSCLD[1:0] bits. 5:2 OSCLF[3:0] Internal L-F Oscillator Frequency Control Bits. Fine-tune control bits for the Internal L-F oscillator frequency. When set to 0000b, the L-F oscillator operates at its fastest setting. When set to 1111b, the L-F oscillator operates at its slowest setting. The OSCLF bits should only be changed by firmware when the L-F oscillator is disabled (OSCLEN=0). 1:0 OSCLD[1:0] Internal L-F Oscillator Divider Select. 00: Divide by 8 selected. 01: Divide by 4 selected. 10: Divide by 2 selected. 11: Divide by 1 selected. 168 Rev. 1.2

C8051F39x/37x 26.4. Internal Low-Power Oscillator All C8051F39x/37x devices include a low-power internal oscillator with a nominal frequency of 20 MHz. The low-power oscillator is automatically enabled when selected as the system clock and disabled when not in use. See Table7.9, “Internal Low-Power Oscillator Electrical Characteristics,” on page38 for com- plete oscillator specifications. 26.5. External Oscillator Drive Circuit The external oscillator circuit may drive an external crystal, ceramic resonator, capacitor, or RC network. A CMOS clock may also provide a clock input. Figure26.1 shows a block diagram of the four external oscil- lator options. The external oscillator is enabled and configured using the OSCXCN register (see SFR Defi- nition 26.5). Important Note on External Oscillator Usage: Port pins must be configured when using the external oscillator circuit. When the external oscillator drive circuit is enabled in crystal/resonator mode, Port pins P0.2 and P0.3 are used as XTAL1 and XTAL2, respectively. When the external oscillator drive circuit is enabled in capacitor, RC, or CMOS clock mode, Port pin P0.3 is used as XTAL2. The Port I/O Crossbar should be configured to skip the Port pin used by the oscillator circuit; see Section “27.3.Priority Crossbar Decoder” on page178 for Crossbar configuration. Additionally, when using the external oscillator circuit in crystal/resonator, capacitor, or RC mode, the associated Port pins should be configured as analog inputs. In CMOS clock mode, the associated pin should be configured as a digital input. See Section “27.4.Port I/O Initialization” on page180 for details on Port input mode selection. The external oscillator output may be selected as the system clock or used to clock some of the digital peripherals (e.g. Timers, PCA, etc.). See the data sheet chapters for each digital peripheral for details. See Section “7.Electrical Characteristics” on page32 for complete oscillator specifications. 26.5.1. External Crystal Mode If a crystal or ceramic resonator is used as the external oscillator, the crystal/resonator and a 10Mresis- tor must be wired across the XTAL1 and XTAL2 pins as shown in Figure26.1, “Crystal Mode”. Appropriate loading capacitors should be added to XTAL1 and XTAL2, and both pins should be configured for analog I/ O with the digital output drivers disabled. The capacitors shown in the external crystal configuration provide the load capacitance required by the crystal for correct oscillation. These capacitors are “in series” as seen by the crystal and “in parallel” with the stray capacitance of the XTAL1 and XTAL2 pins. Note: The recommended load capacitance depends upon the crystal and the manufacturer. Refer to the crystal data sheet when completing these calculations. The equation for determining the load capacitance for two capacitors is C C C = -----A-------------B--+C L C +C S A B Where: C and C are the capacitors connected to the crystal leads. A B C is the total stray capacitance of the PCB. S The stray capacitance for a typical layout where the crystal is as close as possible to the pins is 2-5 pF per pin. If C and C are the same (C), then the equation becomes A B C C = ----+C L 2 S Rev. 1.2 169

C8051F39x/37x For example, a tuning-fork crystal of 32kHz with a recommended load capacitance of 12.5 pF should use the configuration shown in Figure26.1, Option 1. With a stray capacitance of 3 pF per pin (6 pF total), the 13 pF capacitors yield an equivalent capacitance of 12.5 pF across the crystal, as shown in Figure26.2. 13 pF XTAL1 32 kHz 10 M XTAL2 13 pF Figure 26.2. External Crystal Example Important Note on External Crystals: Crystal oscillator circuits are quite sensitive to PCB layout. The crystal should be placed as close as possible to the XTAL pins on the device. The traces should be as short as possible and shielded with ground plane from any other traces which could introduce noise or interference. When using an external crystal, the external oscillator drive circuit must be configured by software for Crys- tal Oscillator Mode or Crystal Oscillator Mode with divide by 2 stage. The divide by 2 stage ensures that the clock derived from the external oscillator has a duty cycle of 50%. The External Oscillator Frequency Con- trol value (XFCN) must also be specified based on the crystal frequency (see SFR Definition 26.5). When the crystal oscillator is first enabled, the external oscillator valid detector allows software to deter- mine when the external system clock is valid and running. Switching to the external oscillator before the crystal oscillator has stabilized can result in unpredictable behavior. The recommended procedure for start- ing the crystal is: 1. Configure XTAL1 and XTAL2 for analog I/O. 2. Disable the XTAL1 and XTAL2 digital output drivers by writing 1s to the appropriate bits in the Port Latch register. 3. Configure and enable the external oscillator. 4. Wait at least 1 ms. 5. Poll for XTLVLD > 1. 6. Switch the system clock to the external oscillator. 170 Rev. 1.2

C8051F39x/37x 26.5.2. External RC Example If an RC network is used as an external oscillator source for the MCU, the circuit should be configured as shown in Figure26.1, “RC Mode”. The capacitor should be no greater than 100pF; however, for very small capacitors, the total capacitance may be dominated by parasitic capacitance in the PCB layout. To deter- mine the required External Oscillator Frequency Control value (XFCN) in the OSCXCN Register, first select the RC network value to produce the desired frequency of oscillation, according to Equation, where f=the frequency of oscillation in MHz, C=the capacitor value in pF, and R=the pull-up resistor value in k. 3 f = 1.2310 RC Equation 26.1. RC Mode Oscillator Frequency For example: If the frequency desired is 100kHz, let R=246k and C=50pF: f=1.23(103)/RC=1.23(103)/[246x50]=0.1MHz=100kHz Referring to the table in SFR Definition 26.5, the required XFCN setting is 010b. 26.5.3. External Capacitor Example If a capacitor is used as an external oscillator for the MCU, the circuit should be configured as shown in Figure26.1, “C Mode”. The capacitor should be no greater than 100pF; however, for very small capaci- tors, the total capacitance may be dominated by parasitic capacitance in the PCB layout. To determine the required External Oscillator Frequency Control value (XFCN) in the OSCXCN Register, select the capaci- tor to be used and find the frequency of oscillation according to Equation, where f=the frequency of oscil- lation in MHz, C=the capacitor value in pF, and V =the MCU power supply in Volts. DD f = KFCV  DD Equation 26.2. C Mode Oscillator Frequency For example: Assume V =3.0V and f=150kHz: DD f=KF / (C x VDD) 0.150MHz=KF / (C x 3.0) Since the frequency of roughly 150 kHz is desired, select the K Factor from the table in SFR Definition 26.5 (OSCXCN) as KF=22: 0.150 MHz=22 / (C x 3.0) C x 3.0=22 / 0.150 MHz C=146.6 / 3.0 pF=48.8 pF Therefore, the XFCN value to use in this example is 011b and C=50 pF. Rev. 1.2 171

C8051F39x/37x SFR Definition 26.5. OSCXCN: External Oscillator Control Bit 7 6 5 4 3 2 1 0 Name XCLKVLD XOSCMD[2:0] XFCN[2:0] Type R R/W R R/W Reset 0 0 0 0 0 0 0 0 SFR Address=0xB1; SFR Page=All Pages Bit Name Function 7 XCLKVLD External Oscillator Valid Flag. Provides External Oscillator status and is valid at all times for all modes of opera- tion except External CMOS Clock Mode and External CMOS Clock Mode with divide by 2. In these modes, XCLKVLD always returns 0. 0: External Oscillator is unused or not yet stable. 1: External Oscillator is running and stable. 6:4 XOSCMD[2:0] External Oscillator Mode Select. 00x: External Oscillator circuit off. 010: External CMOS Clock Mode. 011: External CMOS Clock Mode with divide-by-2 stage. 100: RC Oscillator Mode with divide-by-2 stage. 101: Capacitor Oscillator Mode with divide-by-2 stage. 110: Crystal Oscillator Mode. 111: Crystal Oscillator Mode with divide-by-2 stage. 3 Unused Read=0; Write=don’t care 2:0 XFCN[2:0] External Oscillator Frequency Control Bits. Set according to the desired frequency for RC mode. Set according to the desired K Factor for C mode. XFCN Crystal Mode RC Mode C Mode 000 f 20kHz f 25kHz K Factor=0.87 001 20kHz f 58kHz 25kHz f 50kHz K Factor=2.6 010 58kHz f 155kHz 50kHz f 100kHz K Factor=7.8 011 155kHz f 415kHz 100kHz f 200kHz K Factor=22 100 415kHz f 1.1MHz 200kHz f 400kHz K Factor=66 101 1.1MHz f 3.1MHz 400kHz f 800kHz K Factor=189 110 3.1MHz f 8.2MHz 800kHz f 1.6MHz K Factor=741 111 8.2MHz f 25MHz 1.6MHz f 3.2MHz K Factor=2222 172 Rev. 1.2

C8051F39x/37x 27. Port Input/Output Digital and analog resources are available through 17 (C8051F392/3/6/7/8/9) or 21 (C8051F390/1/4/5 and C8051F37x) I/O pins. Port pins P0.0-P2.3 can be defined as general-purpose I/O (GPIO), assigned to one of the internal digital resources, or assigned to an analog function as shown in Figure27.3. Port pin P2.4 on the C8051F390/1/4/5 and C8051F37x and P2.0 on the C8051F392/3/6/7/8/9 can be used as GPIO and are shared with the C2 Interface Data signal (C2D). The designer has complete control over which func- tions are assigned, limited only by the number of physical I/O pins. This resource assignment flexibility is achieved through the use of a Priority Crossbar Decoder. Note that the state of a Port I/O pin can always be read in the corresponding Port latch, regardless of the Crossbar settings. The Crossbar assigns the selected internal digital resources to the I/O pins based on the Priority Decoder (Figure27.3 and Figure27.4). The registers XBR0 and XBR1, defined in SFR Definition 27.1 and SFR Definition 27.2, are used to select internal digital functions. The Port I/O cells are configured as either push-pull or open-drain in the Port Output Mode registers (PnMDOUT, where n=0,1). Complete Electrical Specifications for Port I/O are given in Section “7.Electrical Characteristics” on page32. Port Match XBR0, XBR1, P0MASK, P0MAT PnSKIP Registers P1MASK, P1MAT External Interrupts Priority EX0 and EX1 Decoder PnMDOUT, 2 PnMDIN Registers Highest UART Priority 4 SPI s) 2 P0.0 al SMBus0 n Digital P0 g Si Crossbar I/O al CP0 2 8 Cells git Outputs Di P0.7 al SYSCLK n (Inter PCA 4 8 P1 P1.0 2 I/O T0, T1 Cells P1.7 Lowest 2 Priority SMBus1 8 P2 P2.0* 4 P0 (P0.0-P0.7) I/O Cell P2.3* es) 8 h c at P1 (P1.0-P1.7) L Port 4 ( P2 (P2.0-P2.3*) To Analog Peripherals *P2.0-P2.3 are only available through (ADC0, CP0, VREF, XTAL) the crossbar on QFN24 Packages. Figure 27.1. Port I/O Functional Block Diagram Rev. 1.2 173

C8051F39x/37x 27.1. Port I/O Modes of Operation Port pins P0.0 - P2.3 use the Port I/O cell shown in Figure27.2. Each Port I/O cell can be configured by software for analog I/O or digital I/O using the PnMDIN registers. On reset, all Port I/O cells default to a high impedance state with weak pull-ups enabled. Until the crossbar is enabled (XBARE=‘1’), both the high and low port I/O drive circuits are explicitly disabled on all crossbar pins. 27.1.1. Port Pins Configured for Analog I/O Any pins to be used as Comparator or ADC input, external oscillator input/output, VREF, or IDAC output should be configured for analog I/O (PnMDIN.n=‘1’). When a pin is configured for analog I/O, its weak pullup, digital driver, and digital receiver are disabled. Port pins configured for analog I/O will always read back a value of ‘0’. Configuring pins as analog I/O saves power and isolates the Port pin from digital interference. Port pins configured as digital I/O may still be used by analog peripherals; however, this practice is not recom- mended and may result in measurement errors. 27.1.2. Port Pins Configured For Digital I/O Any pins to be used by digital peripherals (UART, SPI, SMBus, etc.), external event trigger functions, or as GPIO should be configured as digital I/O (PnMDIN.n=‘1’). For digital I/O pins, one of two output modes (push-pull or open-drain) must be selected using the PnMDOUT registers. Push-pull outputs (PnMDOUT.n=‘1’) drive the Port pad to the VDD or GND supply rails based on the out- put logic value of the Port pin. Open-drain outputs have the high side driver disabled; therefore, they only drive the Port pad to GND when the output logic value is ‘0’ and become high impedance inputs (both high low drivers turned off) when the output logic value is ‘1’. When a digital I/O cell is placed in the high impedance state, a weak pull-up transistor pulls the Port pad to the VDD supply voltage to ensure the digital input is at a defined logic state. Weak pull-ups are disabled when the I/O cell is driven to GND to minimize power consumption, and they may be globally disabled by setting WEAKPUD to ‘1’. The user should ensure that digital I/O are always internally or externally pulled or driven to a valid logic state to minimize power consumption. Port pins configured for digital I/O always read back the logic state of the Port pad, regardless of the output logic value of the Port pin. WEAKPUD (Weak Pull-Up Disable) PxMDOUT.x (1 for push-pull) VDD VDD (0 for open-drain) XBARE (WEAK) (Crossbar Enable) PORT Px.x – Output PAD Logic Value (Port Latch or Crossbar) PxMDIN.x GND (1 for digital) (0 for analog) To/From Analog Peripheral Px.x – Input Logic Value (Reads 0 when pin is configured as an analog I/O) Figure 27.2. Port I/O Cell Block Diagram 174 Rev. 1.2

C8051F39x/37x 27.2. Assigning Port I/O Pins to Analog and Digital Functions Port I/O pins P0.0 - P2.3 can be assigned to various analog, digital, and external interrupt functions. The Port pins assigned to analog functions should be configured for analog I/O, and Port pins assigned to digi- tal or external interrupt functions should be configured for digital I/O. 27.2.1. Assigning Port I/O Pins to Analog Functions Table27.1 shows all available analog functions that require Port I/O assignments. Port pins selected for these analog functions should have their corresponding bit in PnSKIP set to ‘1’. This reserves the pin for use by the analog function and does not allow it to be claimed by the Crossbar. Table27.1 shows the potential mapping of Port I/O to each analog function. Table 27.1. Port I/O Assignment for Analog Functions Analog Function Potentially Assignable SFR(s) used for Port Pins Assignment ADC Input P0.0 - P2.3 AMX0P, AMX0N, PnSKIP, PnMDIN Comparator0 Input P0.0 - P2.3 CPT0MX, PnSKIP, PnMDIN Voltage Reference (VREF0) P0.0 REF0CN, PnSKIP, PnMDIN Current DAC Output (IDA0) P0.1 IDA0CN, PnSKIP, PnMDIN Current DAC Output (IDA1) P1.0 (20-pin devices) IDA1CN, PnSKIP, P1.2 (24-pin devices) PnMDIN External Oscillator in Crystal Mode (XTAL1) P0.2 OSCXCN, PnSKIP, PnMDIN External Oscillator in RC, C, or Crystal Mode (XTAL2) P0.3 OSCXCN, PnSKIP, PnMDIN Rev. 1.2 175

C8051F39x/37x 27.2.2. Assigning Port I/O Pins to Digital Functions Any Port pins not assigned to analog functions may be assigned to digital functions or used as GPIO. Most digital functions rely on the Crossbar for pin assignment; however, some digital functions bypass the Crossbar in a manner similar to the analog functions listed above. Port pins used by these digital func- tions and any Port pins selected for use as GPIO should have their corresponding bit in PnSKIP set to ‘1’. Table27.2 shows all available digital functions and the potential mapping of Port I/O to each digital function. Table 27.2. Port I/O Assignment for Digital Functions Digital Function Potentially Assignable Port Pins SFR(s) Used for Assignment UART0, SPI0, SMBus0, Any Port pin available for assignment by the XBR0, XBR1 SMBus1, CP0, CP0A, Crossbar. This includes P0.0 - P2.3 pins which SYSCLK, PCA0 (CEX0-2 have their PnSKIP bit set to ‘0’. and ECI), T0 or T1. Note: The Crossbar will always assign UART0 pins to P0.4 and P0.5. Any pin used for GPIO P0.0 - P2.4 P0SKIP, P1SKIP, P2SKIP 176 Rev. 1.2

C8051F39x/37x 27.2.3. Assigning Port I/O Pins to External Event Trigger Functions External event trigger functions can be used to trigger an interrupt or wake the device from a low power mode when a transition occurs on a digital I/O pin. The event trigger functions do not require dedicated pins and will function on both GPIO pins (PnSKIP=’1’) and pins in use by the Crossbar (PnSKIP=‘0’). External event trigger functions cannot be used on pins configured for analog I/O. Table27.3 shows all available external event trigger functions. Table 27.3. Port I/O Assignment for External Event Trigger Functions Event Trigger Function Potentially Assignable Port Pins SFR(s) used for Assignment External Interrupt 0 P0.0 - P0.7 IT01CF External Interrupt 1 P0.0 - P0.7 IT01CF Port Match P0.0 - P1.7 P0MASK, P0MAT P1MASK, P1MAT Rev. 1.2 177

C8051F39x/37x 27.3. Priority Crossbar Decoder The Priority Crossbar Decoder (Figure27.3) assigns a priority to each I/O function, starting at the top with UART0. When a digital resource is selected, the least-significant unassigned Port pin is assigned to that resource (excluding UART0, which is always at pins 4 and 5). If a Port pin is assigned, the Crossbar skips that pin when assigning the next selected resource. Additionally, the Crossbar will skip Port pins whose associated bits in the PnSKIP registers are set. The PnSKIP registers allow software to skip Port pins that are to be used for analog input, dedicated functions, or GPIO. Important Note on Crossbar Configuration: If a Port pin is claimed by a peripheral without use of the Crossbar, its corresponding PnSKIP bit should be set. This applies to P0.0 if VREF is used, P0.3 and/or P0.2 if the external oscillator circuit is enabled, P0.6 if the ADC or IDAC is configured to use the external conversion start signal (CNVSTR), and any selected ADC or Comparator inputs. The Crossbar skips selected pins as if they were already assigned, and moves to the next unassigned pin. Figure27.3 shows all of the potential peripheral-to-pin assignments available to the crossbar. Note that this does not mean any peripheral can always be assigned to the highlighted pins. The actual pin assign- ments are determined by the priority of the enabled peripherals. P0 P1 P2 R S(2F0 -Spiing)nals REF DA0 x1 x2 VST DA1 V I N I C S(2F4 -Spiing)nals REF DA0 x1 x2 VSTR DA1 5SCL 5SDA V I N I E E C E E PIN I/O 0 1 2 3 4 5 6 7 0 1 2 3 4 5 6 7 04 1 3 2 3 3 3 43 TX0 RX0 SCK MISO MOSI s. al NSS1 er h p SDA02 eri p SCL02 ar b CP0 s s o CP0A cr SYSCLK e for CEX0 bl a CEX1 vail a CEX2 ot n ECI n Pi T0 T1 SDA12 SCL12 Port pin potentially available to peripheral Notes: SF Signals Special Function Signals are not assigned by the crossbar. 1. NSS is only pinned out in 4-wire SPI Mode When these signals are enabled, the Crossbar must be 2. SMBus pins can be re-ordered using SMBTC register manually configured to skip their corresponding port pins. 3. Pins P2.1-P2.4 only on QFN24 Package 4. Pin 2.0 unavailable on crossbar in QFN20 Package 5. C8051F37x only Figure 27.3. Crossbar Priority Decoder - Possible Pin Assignments 178 Rev. 1.2

C8051F39x/37x Registers XBR0 and XBR1 are used to assign the digital I/O resources to the physical I/O Port pins. Note that when the SMBus is selected, the Crossbar assigns both pins associated with the SMBus (SDA and SCL); when the UART is selected, the Crossbar assigns both pins associated with the UART (TX and RX). UART0 pin assignments are fixed for bootloading purposes: UART TX0 is always assigned to P0.4; UART RX0 is always assigned to P0.5. Standard Port I/Os appear contiguously after the prioritized functions have been assigned. Figure27.4 shows an example of the resulting pin assignments of the device with UART0, SMBus, and CEX0 enabled, the XTAL1 (P0.2) and XTAL2 (P0.3) pins skipped (P0SKIP=0x0C). UART0 is the highest priority and it will be assigned first. The UART can only appear on P0.4 and P0.5, so that is where it is assigned. The next-highest enabled peripheral is SMBus0. P0.0 and P0.1 are free, so SMBus0 takes these two pins. The last peripheral enabled is the PCA’s CEX0 pin. P0.0, P0.1, P0.4 and P0.5 are already occupied by higher-priority peripherals. Additionally, P0.2 and P0.3 are set to be skipped by the crossbar. The CEX0 signal ends up getting routed to P0.6, as it is the next available pin. The other pins on the device are available for use as general-purpose digital I/O or analog functions. P0 P1 P2 R S(2F0 -Spiing)nals REF DA0 x1 x2 VST DA1 V I CN I S(2F4 -Spiing)nals REF DA0 x1 x2 VSTR DA1 5SCL 5SDA V I CN I EE EE PIN I/O 0 1 2 3 4 5 6 7 0 1 2 3 4 5 6 7 0 1 2 2 2 3 2 4 2 TX0 RX0 SCK MISO MOSI s. al NSS1 er h p SDA eri p SCL ar b CP0 s s o CP0A cr SYSCLK e for CEX0 abl CEX1 vail a CEX2 ot n ECI n Pi T0 T1 SDA12 SCL12 0 0 1 1 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 P0SKIP[0:7] P1SKIP[0:7] P2SKIP[0:3] Port pin potentially available to peripheral Notes: SF Signals Special Function Signals are not assigned by the crossbar. 1. NSS is only pinned out in 4-wire SPI Mode When these signals are enabled, the CrossBar must be 2. SMBus pins can be re-ordered using SMBTC register manually configured to skip their corresponding port pins. 3. Pins P2.1-P2.4 only on QFN24 Package 4. Pin 2.0 unavailable on crossbar in QFN20 Package 5. C8051F37x only Figure 27.4. Crossbar Priority Decoder Example Important Notes: The SPI can be operated in either 3-wire or 4-wire modes, pending the state of the NSS- MD1–NSSMD0 bits in register SPI0CN. According to the SPI mode, the NSS signal may or may not be routed to a Port pin. The order in which SMBus pins are assigned is defined by the SMBnSWAP bits in the SMBTC register. Rev. 1.2 179

C8051F39x/37x 27.4. Port I/O Initialization Port I/O initialization consists of the following steps: 1. Select the input mode (analog or digital) for all Port pins, using the Port Input Mode register (PnMDIN). 2. Select the output mode (open-drain or push-pull) for all Port pins, using the Port Output Mode register (PnMDOUT). 3. Select any pins to be skipped by the I/O Crossbar using the Port Skip registers (PnSKIP). 4. Assign Port pins to desired peripherals. 5. Enable the Crossbar (XBARE=‘1’). All Port pins must be configured as either analog or digital inputs. Any pins to be used as Comparator or ADC inputs should be configured as an analog inputs. When a pin is configured as an analog input, its weak pullup, digital driver, and digital receiver are disabled. This process saves power and reduces noise on the analog input. Pins configured as digital inputs may still be used by analog peripherals; however this practice is not recommended. Additionally, all analog input pins should be configured to be skipped by the Crossbar (accomplished by setting the associated bits in PnSKIP). Port input mode is set in the PnMDIN register, where a ‘1’ indicates a digital input, and a ‘0’ indicates an analog input. All pins default to digital inputs on reset. See SFR Defini- tion 27.8 for the PnMDIN register details. The output driver characteristics of the I/O pins are defined using the Port Output Mode registers (PnMD- OUT). Each Port Output driver can be configured as either open drain or push-pull. This selection is required even for the digital resources selected in the XBRn registers, and is not automatic. The only exception to this is the SMBus (SDA, SCL) pins, which are configured as open-drain regardless of the PnMDOUT settings. When the WEAKPUD bit in XBR1 is ‘0’, a weak pullup is enabled for all Port I/O con- figured as open-drain. WEAKPUD does not affect the push-pull Port I/O. Furthermore, the weak pullup is turned off on an output that is driving a ‘0’ to avoid unnecessary power dissipation. Registers XBR0 and XBR1 must be loaded with the appropriate values to select the digital I/O functions required by the design. Setting the XBARE bit in XBR1 to ‘1’ enables the Crossbar. Until the Crossbar is enabled, the external pins remain as standard Port I/O (in input mode), regardless of the XBRn Register settings. For given XBRn Register settings, one can determine the I/O pin-out using the Priority Decode Table; as an alternative, the Configuration Wizard utility of the Silicon Labs IDE software will determine the Port I/O pin-assignments based on the XBRn Register settings. The Crossbar must be enabled to use Port pins as standard Port I/O in output mode. Port output drivers are disabled while the Crossbar is disabled. 180 Rev. 1.2

C8051F39x/37x SFR Definition 27.1. XBR0: Port I/O Crossbar Register 0 Bit 7 6 5 4 3 2 1 0 Name EEPUE SMB1E CP0AE CP0E SYSCKE SMB0E SPI0E URT0E Type R/W R/W R/W R/W R/W R/W R/W R/W Reset 0 0 0 0 0 0 0 0 SFR Address=0xE1; SFR Page=All Pages Bit Name Function 7 EEPUE EEPROM Pullup Enable. 0: On-chip strong pullups not active. 1: On-chip strong pullups active on pins P2.2 and P2.3. 6 SMB1E SMBus1 I/O Enable. 0: SMBus1 I/O unavailable at Port pins. 1: SMBus1 I/O routed to Port pins. 5 CP0AE Comparator0 Asynchronous Output Enable. 0: Asynchronous CP0 unavailable at Port pin. 1: Asynchronous CP0 routed to Port pin. 4 CP0E Comparator0 Output Enable. 0: CP0 unavailable at Port pin. 1: CP0 routed to Port pin. 3 SYSCKE /SYSCLK Output Enable. 0: /SYSCLK unavailable at Port pin. 1: /SYSCLK output routed to Port pin. 2 SMB0E SMBus0 I/O Enable. 0: SMBus0 I/O unavailable at Port pins. 1: SMBus0 I/O routed to Port pins. 1 SPI0E SPI I/O Enable. 0: SPI I/O unavailable at Port pins. 1: SPI I/O routed to Port pins. Note that the SPI can be assigned either 3 or 4 GPIO pins. 0 URT0E UART I/O Output Enable. 0: UART I/O unavailable at Port pin. 1: UART TX0, RX0 routed to Port pins P0.4 and P0.5. Rev. 1.2 181

C8051F39x/37x SFR Definition 27.2. XBR1: Port I/O Crossbar Register 1 Bit 7 6 5 4 3 2 1 0 Name WEAKPUD XBARE T1E T0E ECIE PCA0ME[1:0] Type R/W R/W R/W R/W R/W R R/W R/W Reset 0 0 0 0 0 0 0 0 SFR Address=0xE2; SFR Page=All Pages Bit Name Function 7 WEAKPUD Port I/O Weak Pullup Disable. 0: Weak Pullups enabled (except for Ports whose I/O are con- figured for analog mode). 1: Weak Pullups disabled. 6 XBARE Crossbar Enable. 0: Crossbar disabled. 1: Crossbar enabled. 5 T1E T1 Enable. 0: T1 unavailable at Port pin. 1: T1 routed to Port pin. 4 T0E T0 Enable. 0: T0 unavailable at Port pin. 1: T0 routed to Port pin. 3 ECIE PCA0 External Counter Input Enable. 0: ECI unavailable at Port pin. 1: ECI routed to Port pin. 2 Unused Read=0b; Write=Don’t Care. 1:0 PCA0ME[1:0] PCA Module I/O Enable Bits. 00: All PCA I/O unavailable at Port pins. 01: CEX0 routed to Port pin. 10: CEX0, CEX1 routed to Port pins. 11: CEX0, CEX1, CEX2 routed to Port pins. 182 Rev. 1.2

C8051F39x/37x 27.5. Port Match Port match functionality allows system events to be triggered by a logic value change on P0 or P1. A soft- ware controlled value stored in the PnMATCH registers specifies the expected or normal logic values of P0 and P1. A Port mismatch event occurs if the logic levels of the Port’s input pins no longer match the soft- ware controlled value. This allows Software to be notified if a certain change or pattern occurs on P0 or P1 input pins regardless of the XBRn settings. The PnMASK registers can be used to individually select which P0 and P1 pins should be compared against the PnMATCH registers. A Port mismatch event is generated if (P0&P0MASK) does not equal (P0MATCH&P0MASK) or if (P1&P1MASK) does not equal (P1MATCH&P1MASK). A Port mismatch event may be used to generate an interrupt or wake the device from a low power mode, such as IDLE or SUSPEND. See the Interrupts and Power Options chapters for more details on interrupt and wake-up sources. SFR Definition 27.3. P0MASK: Port 0 Mask Register Bit 7 6 5 4 3 2 1 0 Name P0MASK[7:0] Type R/W Reset 0 0 0 0 0 0 0 0 SFR Address=0xFE; SFR Page=All Pages Bit Name Function 7:0 P0MASK[7:0] Port 0 Mask Value. Selects P0 pins to be compared to the corresponding bits in P0MAT. 0: P0.n pin logic value is ignored and cannot cause a Port Mismatch event. 1: P0.n pin logic value is compared to P0MAT.n. Rev. 1.2 183

C8051F39x/37x SFR Definition 27.4. P0MAT: Port 0 Match Register Bit 7 6 5 4 3 2 1 0 Name P0MAT[7:0] Type R/W Reset 1 1 1 1 1 1 1 1 SFR Address=0xFD; SFR Page=All Pages Bit Name Function 7:0 P0MAT[7:0] Port 0 Match Value. Match comparison value used on Port 0 for bits in P0MASK which are set to ‘1’. 0: P0.n pin logic value is compared with logic LOW. 1: P0.n pin logic value is compared with logic HIGH. SFR Definition 27.5. P1MASK: Port 1 Mask Register Bit 7 6 5 4 3 2 1 0 Name P1MASK[7:0] Type R/W Reset 0 0 0 0 0 0 0 0 SFR Address=0xEE; SFR Page=All Pages Bit Name Function 7:0 P1MASK[7:0] Port 1 Mask Value. Selects P1 pins to be compared to the corresponding bits in P1MAT. 0: P1.n pin logic value is ignored and cannot cause a Port Mismatch event. 1: P1.n pin logic value is compared to P1MAT.n. 184 Rev. 1.2

C8051F39x/37x SFR Definition 27.6. P1MAT: Port 1 Match Register Bit 7 6 5 4 3 2 1 0 Name P1MAT[7:0] Type R/W Reset 1 1 1 1 1 1 1 1 SFR Address=0xED; SFR Page=All Pages Bit Name Function 7:0 P1MAT[7:0] Port 1 Match Value. Match comparison value used on Port 1 for bits in P1MASK which are set to ‘1’. 0: P1.n pin logic value is compared with logic LOW. 1: P1.n pin logic value is compared with logic HIGH. 27.6. Special Function Registers for Accessing and Configuring Port I/O All Port I/O are accessed through corresponding special function registers (SFRs) that are both byte addressable and bit addressable. When writing to a Port, the value written to the SFR is latched to main- tain the output data value at each pin. When reading, the logic levels of the Port's input pins are returned regardless of the XBRn settings (i.e., even when the pin is assigned to another signal by the Crossbar, the Port register can always read its corresponding Port I/O pin). The exception to this is the execution of the read-modify-write instructions that target a Port Latch register as the destination. The read-modify-write instructions when operating on a Port SFR are the following: ANL, ORL, XRL, JBC, CPL, INC, DEC, DJNZ and MOV, CLR or SETB, when the destination is an individual bit in a Port SFR. For these instructions, the value of the latch register (not the pin) is read, modified, and written back to the SFR. Each Port has a corresponding PnSKIP register which allows its individual Port pins to be assigned to dig- ital functions or skipped by the Crossbar. All Port pins used for analog functions, GPIO, or dedicated digital functions such as the EMIF should have their PnSKIP bit set to ‘1’. The Port input mode of the I/O pins is defined using the Port Input Mode registers (PnMDIN). Each Port cell can be configured for analog or digital I/O. This selection is required even for the digital resources selected in the XBRn registers, and is not automatic. The only exception to this is P2.4, which can only be used for digital I/O. The output driver characteristics of the I/O pins are defined using the Port Output Mode registers (PnMD- OUT). Each Port Output driver can be configured as either open drain or push-pull. This selection is required even for the digital resources selected in the XBRn registers, and is not automatic. The only exception to this is the SMBus (SDA, SCL) pins, which are configured as open-drain regardless of the PnMDOUT settings. Rev. 1.2 185

C8051F39x/37x SFR Definition 27.7. P0: Port 0 Bit 7 6 5 4 3 2 1 0 Name P0[7:0] Type R/W Reset 1 1 1 1 1 1 1 1 SFR Address=0x80; SFR Page=All Pages; Bit Addressable Bit Name Description Write Read 7:0 P0[7:0] Port 0 Data. 0: Set output latch to logic 0: P0.n Port pin is logic LOW. LOW. Sets the Port latch logic 1: Set output latch to logic 1: P0.n Port pin is logic value or reads the Port pin HIGH. HIGH. logic state in Port cells con- figured for digital I/O. SFR Definition 27.8. P0MDIN: Port 0 Input Mode Bit 7 6 5 4 3 2 1 0 Name P0MDIN[7:0] Type R/W Reset 1 1 1 1 1 1 1 1 SFR Address=0xF1; SFR Page=All Pages Bit Name Function 7:0 P0MDIN[7:0] Analog Configuration Bits for P0.7–P0.0 (respectively). Port pins configured for analog mode have their weak pul- lup, digital driver, and digital receiver disabled. 0: Corresponding P0.n pin is configured for analog mode. 1: Corresponding P0.n pin is not configured for analog mode. 186 Rev. 1.2

C8051F39x/37x SFR Definition 27.9. P0MDOUT: Port 0 Output Mode Bit 7 6 5 4 3 2 1 0 Name P0MDOUT[7:0] Type R/W Reset 0 0 0 0 0 0 0 0 SFR Address=0xA4; SFR Page=All Pages Bit Name Function 7:0 P0MDOUT[7:0] Output Configuration Bits for P0.7–P0.0 (respectively). These bits are ignored if the corresponding bit in register P0MDIN is logic 0. 0: Corresponding P0.n Output is open-drain. 1: Corresponding P0.n Output is push-pull. SFR Definition 27.10. P0SKIP: Port 0 Skip Bit 7 6 5 4 3 2 1 0 Name P0SKIP[7:0] Type R/W Reset 0 0 0 0 0 0 0 0 SFR Address=0xD4; SFR Page=All Pages Bit Name Function 7:0 P0SKIP[7:0] Port 0 Crossbar Skip Enable Bits. These bits select Port 0 pins to be skipped by the Crossbar Decoder. Port pins used for analog, special functions or GPIO should be skipped by the Crossbar. 0: Corresponding P0.n pin is not skipped by the Crossbar. 1: Corresponding P0.n pin is skipped by the Crossbar. Rev. 1.2 187

C8051F39x/37x SFR Definition 27.11. P1: Port 1 Bit 7 6 5 4 3 2 1 0 Name P1[7:0] Type R/W Reset 1 1 1 1 1 1 1 1 SFR Address=0x90; SFR Page=All Pages; Bit Addressable Bit Name Description Write Read 7:0 P1[7:0] Port 1 Data. 0: Set output latch to logic 0: P1.n Port pin is logic LOW. LOW. Sets the Port latch logic 1: Set output latch to logic 1: P1.n Port pin is logic value or reads the Port pin HIGH. HIGH. logic state in Port cells con- figured for digital I/O. SFR Definition 27.12. P1MDIN: Port 1 Input Mode Bit 7 6 5 4 3 2 1 0 Name P1MDIN[7:0] Type R/W Reset 1 1 1 1 1 1 1 1 SFR Address=0xF2; SFR Page=All Pages Bit Name Function 7:0 P1MDIN[7:0] Analog Configuration Bits for P1.7–P1.0 (respectively). Port pins configured for analog mode have their weak pul- lup, digital driver, and digital receiver disabled. 0: Corresponding P1.n pin is configured for analog mode. 1: Corresponding P1.n pin is not configured for analog mode. 188 Rev. 1.2

C8051F39x/37x SFR Definition 27.13. P1MDOUT: Port 1 Output Mode Bit 7 6 5 4 3 2 1 0 Name P1MDOUT[7:0] Type R/W Reset 0 0 0 0 0 0 0 0 SFR Address=0xA5; SFR Page=All Pages Bit Name Function 7:0 P1MDOUT[7:0] Output Configuration Bits for P1.7–P1.0 (respectively). These bits are ignored if the corresponding bit in register P1MDIN is logic 0. 0: Corresponding P1.n Output is open-drain. 1: Corresponding P1.n Output is push-pull. SFR Definition 27.14. P1SKIP: Port 1 Skip Bit 7 6 5 4 3 2 1 0 Name P1SKIP[7:0] Type R/W Reset 0 0 0 0 0 0 0 0 SFR Address=0xD5; SFR Page=All Pages Bit Name Function 7:0 P1SKIP[7:0] Port 1 Crossbar Skip Enable Bits. These bits select Port 1 pins to be skipped by the Crossbar Decoder. Port pins used for analog, special functions or GPIO should be skipped by the Crossbar. 0: Corresponding P1.n pin is not skipped by the Crossbar. 1: Corresponding P1.n pin is skipped by the Crossbar. Rev. 1.2 189

C8051F39x/37x SFR Definition 27.15. P2: Port 2 Bit 7 6 5 4 3 2 1 0 Name P2[4:0] Type R R R R/W Reset 0 0 0 1 1 1 1 1 SFR Address=0xA0; SFR Page=All Pages; Bit Addressable Bit Name Description Write Read 7:5 Unused Unused. Don’t Care 000b 4:0 P2[4:0] Port 2 Data. 0: Set output latch to logic 0: P2.n Port pin is logic LOW. LOW. Sets the Port latch logic value or reads the Port pin 1: Set output latch to logic 1: P2.n Port pin is logic logic state in Port cells con- HIGH. HIGH. figured for digital I/O. Note: Pins P2.1-P2.4 are only available in QFN24-packaged devices. SFR Definition 27.16. P2MDIN: Port 2 Input Mode Bit 7 6 5 4 3 2 1 0 Name P2MDIN[7:0] Type R R R R R/W Reset 0 0 0 0 1 1 1 1 SFR Address=0xF3; SFR Page=All Pages Bit Name Function 7:4 Unused Read=0000b; Write=Don’t Care 3:0 P2MDIN[3:0] Analog Configuration Bits for P2.3–P2.0 (respectively). Port pins configured for analog mode have their weak pullup, digital driver, and digital receiver disabled. 0: Corresponding P2.n pin is configured for analog mode. 1: Corresponding P2.n pin is not configured for analog mode. Note: Pins P2.1-P2.4 are only available in QFN24-packaged devices. 190 Rev. 1.2

C8051F39x/37x SFR Definition 27.17. P2MDOUT: Port 2 Output Mode Bit 7 6 5 4 3 2 1 0 Name P2MDOUT[4:0] Type R R R R/W Reset 0 0 0 0 0 0 0 0 SFR Address=0xA6; SFR Page=All Pages Bit Name Function 7:5 Unused Read=000b; Write=Don’t Care 4:0 P2MDOUT[4:0] Output Configuration Bits for P2.4–P2.0 (respectively). These bits are ignored if the corresponding bit in register P2MDIN is logic 0. 0: Corresponding P2.n Output is open-drain. 1: Corresponding P2.n Output is push-pull. Note: P2.0 is not available for analog input in the QFN20-packaged devices, and P2.1-P2.4 are only available in the QFN24-packaged devices. SFR Definition 27.18. P2SKIP: Port 2 Skip Bit 7 6 5 4 3 2 1 0 Name P2SKIP[7:0] Type R R R R R/W Reset 0 0 0 0 0 0 0 0 SFR Address=0xD6; SFR Page=All Pages Bit Name Function 7:4 Unused Read=0000b; Write=Don’t Care 3:0 P2SKIP[3:0] Port 2 Crossbar Skip Enable Bits. These bits select Port 2 pins to be skipped by the Crossbar Decoder. Port pins used for analog, special functions or GPIO should be skipped by the Crossbar. 0: Corresponding P2.n pin is not skipped by the Crossbar. 1: Corresponding P2.n pin is skipped by the Crossbar. Note: P2.0 is not available for crossbar peripherals in the QFN20-packaged devices, and P2.1-P2.4 are only available in the QFN24-packaged devices. Rev. 1.2 191

C8051F39x/37x 2 28. SMBus0 and SMBus1 (I C Compatible) The SMBus I/O interface is a two-wire, bi-directional serial bus. The SMBus is compliant with the System Management Bus Specification, version1.1, and compatible with the I2C serial bus. The C8051F39x/37x devices contain two SMBus interfaces, SMBus0 and SMBus1. Reads and writes to the SMBus by the system controller are byte oriented with the SMBus interface auton- omously controlling the serial transfer of the data. Data can be transferred at up to 1/20th of the system clock as a master or slave (this can be faster than allowed by the SMBus specification, depending on the system clock used). A method of extending the clock-low duration is available to accommodate devices with different speed capabilities on the same bus. The SMBus may operate as a master and/or slave, and may function on a bus with multiple masters. The SMBus provides control of SDA (serial data), SCL (serial clock) generation and synchronization, arbitration logic, and START/STOP control and generation. The SMBus peripherals can be fully driven by software (i.e., software accepts/rejects slave addresses, and generates ACKs), or hardware slave address recogni- tion and automatic ACK generation can be enabled to minimize software overhead. A block diagram of the SMBus0 peripheral and the associated SFRs is shown in Figure28.1. SMBus1 is identical, with the excep- tion of the available timer options for the clock source, and the timer used to implement the SCL low time- out feature. Refer to the specific SFR definitions for more details. SMB0CN SMB0CF MT SSAAAS E I BESSSS AX T TCRC I NN UXMMMM SMAOKBK SHS T BBBB TO R L M YHT FCC ED QO B OOT SS RE S L EE 1 0 T D 00 T0 Overflow 01 T1 Overflow 10 TMR2H Overflow 11 TMR2L Overflow SCL SMBUS CONTROL LOGIC FILTER Interrupt Arbitration Request SCL Synchronization SCL Generation (Master Mode) SCL N C SDA Control Control R Hardware Slave Address Recognition O Hardware ACK Generation S IRQ Generation Data Path SDA S Port I/O Control Control B A R SMB0DAT SDA 7 6 5 4 3 2 1 0 FILTER SSSSSSSG SSSSSSSE L L L L L L L C L L L L L L L H VVVVVVV VVVVVVVA 6 5 4 3 2 1 0 MMMMMMMC 6 5 4 3 2 1 0 K SMB0ADR SMB0ADM N Figure 28.1. SMBus0 Block Diagram 192 Rev. 1.2

C8051F39x/37x 28.1. Supporting Documents It is assumed the reader is familiar with or has access to the following supporting documents: 1. The I2C-Bus and How to Use It (including specifications), Philips Semiconductor. 2. The I2C-Bus Specification—Version 2.0, Philips Semiconductor. 3. System Management Bus Specification—Version 1.1, SBS Implementers Forum. 28.2. SMBus Configuration Figure28.2 shows a typical SMBus configuration. The SMBus specification allows any recessive voltage between 3.0V and 5.0V; different devices on the bus may operate at different voltage levels. However, the maximum voltage on any port pin must conform to Table7.1. The bi-directional SCL (serial clock) and SDA (serial data) lines must be connected to a positive power supply voltage through a pullup resistor or similar circuit. Every device connected to the bus must have an open-drain or open-collector output for both the SCL and SDA lines, so that both are pulled high (recessive state) when the bus is free. The maximum number of devices on the bus is limited only by the requirement that the rise and fall times on the bus not exceed 300ns and 1000ns, respectively. 3.0V < VDD < 3.6V Master Slave Slave Device Device 1 Device 2 SDA SCL Figure 28.2. Typical SMBus Configuration 28.3. SMBus Operation Two types of data transfers are possible: data transfers from a master transmitter to an addressed slave receiver (WRITE), and data transfers from an addressed slave transmitter to a master receiver (READ). The master device initiates both types of data transfers and provides the serial clock pulses on SCL. The SMBus interface may operate as a master or a slave, and multiple master devices on the same bus are supported. If two or more masters attempt to initiate a data transfer simultaneously, an arbitration scheme is employed with a single master always winning the arbitration. It is not necessary to specify one device as the Master in a system; any device who transmits a START and a slave address becomes the master for the duration of that transfer. A typical SMBus transaction consists of a START condition followed by an address byte (Bits7–1: 7-bit slave address; Bit0: R/W direction bit), one or more bytes of data, and a STOP condition. Bytes that are received (by a master or slave) are acknowledged (ACK) with a low SDA during a high SCL (see Figure28.3). If the receiving device does not ACK, the transmitting device will read a NACK (not acknowl- edge), which is a high SDA during a high SCL. The direction bit (R/W) occupies the least-significant bit position of the address byte. The direction bit is set to logic 1 to indicate a "READ" operation and cleared to logic 0 to indicate a "WRITE" operation. Rev. 1.2 193

C8051F39x/37x All transactions are initiated by a master, with one or more addressed slave devices as the target. The master generates the START condition and then transmits the slave address and direction bit. If the trans- action is a WRITE operation from the master to the slave, the master transmits the data a byte at a time waiting for an ACK from the slave at the end of each byte. For READ operations, the slave transmits the data waiting for an ACK from the master at the end of each byte. At the end of the data transfer, the master generates a STOP condition to terminate the transaction and free the bus. Figure28.3 illustrates a typical SMBus transaction. SCL SDA SLA6 SLA5-0 R/W D7 D6-0 START Slave Address + R/W ACK Data Byte NACK STOP Figure 28.3. SMBus Transaction 28.3.1. Transmitter vs. Receiver On the SMBus communications interface, a device is the “transmitter” when it is sending an address or data byte to another device on the bus. A device is a “receiver” when an address or data byte is being sent to it from another device on the bus. The transmitter controls the SDA line during the address or data byte. After each byte of address or data information is sent by the transmitter, the receiver sends an ACK or NACK bit during the ACK phase of the transfer, during which time the receiver controls the SDA line. 28.3.2. Arbitration A master may start a transfer only if the bus is free. The bus is free after a STOP condition or after the SCL and SDA lines remain high for a specified time (see Section “28.3.5.SCL High (SMBus Free) Timeout” on page195). In the event that two or more devices attempt to begin a transfer at the same time, an arbitra- tion scheme is employed to force one master to give up the bus. The master devices continue transmitting until one attempts a HIGH while the other transmits a LOW. Since the bus is open-drain, the bus will be pulled LOW. The master attempting the HIGH will detect a LOW SDA and lose the arbitration. The winning master continues its transmission without interruption; the losing master becomes a slave and receives the rest of the transfer if addressed. This arbitration scheme is non-destructive: one device always wins, and no data is lost. 28.3.3. Clock Low Extension SMBus provides a clock synchronization mechanism, similar to I2C, which allows devices with different speed capabilities to coexist on the bus. A clock-low extension is used during a transfer in order to allow slower slave devices to communicate with faster masters. The slave may temporarily hold the SCL line LOW to extend the clock low period, effectively decreasing the serial clock frequency. 28.3.4. SCL Low Timeout If the SCL line is held low by a slave device on the bus, no further communication is possible. Furthermore, the master cannot force the SCL line high to correct the error condition. To solve this problem, the SMBus protocol specifies that devices participating in a transfer must detect any clock cycle held low longer than 25ms as a “timeout” condition. Devices that have detected the timeout condition must reset the communi- cation no later than 10ms after detecting the timeout condition. For the SMBus0 interface, Timer3 is used to implement SCL low timeouts. Timer4 is used on the SMBus1 interface for SCL low timeouts. The SCL low timeout feature is enabled by setting the SMBnTOE bit in SMBnCF. The associated timer is forced to reload when SCL is high, and allowed to count when SCL is 194 Rev. 1.2

C8051F39x/37x low. With the associated timer enabled and configured to overflow after 25ms (and SMBnTOE set), the timer interrupt service routine can be used to reset (disable and re-enable) the SMBus in the event of an SCL low timeout. 28.3.5. SCL High (SMBus Free) Timeout The SMBus specification stipulates that if the SCL and SDA lines remain high for more that 50µs, the bus is designated as free. When the SMBnFTE bit in SMBnCF is set, the bus will be considered free if SCL and SDA remain high for more than 10SMBus clock source periods (as defined by the timer configured for the SMBus clock source). If the SMBus is waiting to generate a Master START, the START will be generated following this timeout. A clock source is required for free timeout detection, even in a slave-only implemen- tation. 28.4. Using the SMBus The SMBus can operate in both Master and Slave modes. The interface provides timing and shifting con- trol for serial transfers; higher level protocol is determined by user software. The SMBus interface provides the following application-independent features:  Byte-wise serial data transfers  Clock signal generation on SCL (Master Mode only) and SDA data synchronization  Timeout/bus error recognition, as defined by the SMB0CF configuration register  START/STOP timing, detection, and generation  Bus arbitration  Interrupt generation  Status information  Optional hardware recognition of slave address and automatic acknowledgement of address/data SMBus interrupts are generated for each data byte or slave address that is transferred. When hardware acknowledgment is disabled, the point at which the interrupt is generated depends on whether the hard- ware is acting as a data transmitter or receiver. When a transmitter (i.e., sending address/data, receiving an ACK), this interrupt is generated after the ACK cycle so that software may read the received ACK value; when receiving data (i.e., receiving address/data, sending an ACK), this interrupt is generated before the ACK cycle so that software may define the outgoing ACK value. If hardware acknowledgment is enabled, these interrupts are always generated after the ACK cycle. See Section 28.5 for more details on transmis- sion sequences. Interrupts are also generated to indicate the beginning of a transfer when a master (START generated), or the end of a transfer when a slave (STOP detected). Software should read the SMBnCN (SMBus Control register) to find the cause of the SMBus interrupt. The SMBnCN register is described in Section 28.4.4; Table28.5 provides a quick SMBnCN decoding reference. 28.4.1. SMBus Configuration Register The SMBus Configuration register (SMBnCF) is used to enable the SMBus Master and/or Slave modes, select the SMBus clock source, and select the SMBus timing and timeout options. When the ENSMB bit is set, the SMBus is enabled for all master and slave events. Slave events may be disabled by setting the INH bit. With slave events inhibited, the SMBus interface will still monitor the SCL and SDA pins; however, the interface will NACK all received addresses and will not generate any slave interrupts. When the INH bit is set, all slave events will be inhibited following the next START (interrupts will continue for the duration of the current transfer). Rev. 1.2 195

C8051F39x/37x Table 28.1. SMBus Clock Source Selection SMBnCS1 SMBnCS0 SMBus0 Clock Source SMBus1 Clock Source 0 0 Timer 0 Overflow Timer 0 Overflow 0 1 Timer 1 Overflow Timer 5 Overflow 1 0 Timer 2 High Byte Overflow Timer 2 High Byte Overflow 1 1 Timer 2 Low Byte Overflow Timer 2 Low Byte Overflow The SMBnCS1–0 bits select the SMBus clock source, which is used only when operating as a master or when the Free Timeout detection is enabled. When operating as a master, overflows from the selected source determine the absolute minimum SCL low and high times as defined in Equation28.1.The selected clock source may be shared by other peripherals so long as the timer is left running at all times. For exam- ple, Timer1 overflows may generate the SMBus0 and SMBus1 clock rates simultaneously. Timer configu- ration is covered in Section “31.Timers” on page242. 1 T = T = ---------------------------------------------- HighMin LowMin f ClockSourceOverflow Equation 28.1. Minimum SCL High and Low Times The selected clock source should be configured to establish the minimum SCL High and Low times as per Equation28.1. When the interface is operating as a master (and SCL is not driven or extended by any other devices on the bus), the typical SMBus bit rate is approximated by Equation28.2. f BitRate = --C----l-o---c--k--S---o--u---r--c--e--O----v--e--r--f--l-o---w-- 3 Equation 28.2. Typical SMBus Bit Rate Figure28.4 shows the typical SCL generation described by Equation28.2. Notice that T is typically HIGH twice as large as T . The actual SCL output may vary due to other devices on the bus (SCL may be LOW extended low by slower slave devices, or driven low by contending master devices). The bit rate when operating as a master will never exceed the limits defined by equation Equation28.1. Timer Source Overflows SCL T T SCL High Timeout Low High Figure 28.4. Typical SMBus SCL Generation Setting the EXTHOLD bit extends the minimum setup and hold times for the SDA line. The minimum SDA setup time defines the absolute minimum time that SDA is stable before SCL transitions from low-to-high. The minimum SDA hold time defines the absolute minimum time that the current SDA value remains stable after SCL transitions from high-to-low. EXTHOLD should be set so that the minimum setup and hold times meet the SMBus Specification requirements of 250ns and 300ns, respectively. Table28.2 shows the min- 196 Rev. 1.2

C8051F39x/37x imum setup and hold times for the two EXTHOLD settings. Setup and hold time extensions are typically necessary when SYSCLK is above 10MHz. Table 28.2. Minimum SDA Setup and Hold Times EXTHOLD Minimum SDA Setup Time Minimum SDA Hold Time T – 4 system clocks low 0 or 3 system clocks 1 system clock + s/w delay* 1 11 system clocks 12 system clocks Note: Setup Time for ACK bit transmissions and the MSB of all data transfers. When using software acknowledgement, the s/w delay occurs between the time SMB0DAT or ACK is written and when SI is cleared. Note that if SI is cleared in the same write that defines the outgoing ACK value, s/w delay is zero. With the SMBnTOE bit set, Timer3 (SMBus0) and Timer5 (SMBus1) should be configured to overflow after 25ms in order to detect SCL low timeouts (see Section “28.3.4.SCL Low Timeout” on page194). The SMBus interface will force the associated timer to reload while SCL is high, and allow the timer to count when SCL is low. The timer interrupt service routine should be used to reset SMBus communication by disabling and re-enabling the SMBus. SMBus Free Timeout detection can be enabled by setting the SMBnFTE bit. When this bit is set, the bus will be considered free if SDA and SCL remain high for more than 10SMBus clock source periods (see Figure28.4). 28.4.2. SMBus Pin Swap The SMBus peripherals are assigned to pins using the priority crossbar decoder. By default, the SMBus signals are assigned to port pins starting with SDA on the lower-numbered pin, and SCL on the next avail- able pin. The SMBnSWAP bits in the SMBTC register can be set to 1 to reverse the order in which the SMBus signals are assigned. 28.4.3. SMBus Timing Control The SMBnSDD field in the SMBTC register are used to restrict the detection of a START condition under certain circumstances. In some systems where there is significant mis-match between the impedance or the capacitance on the SDA and SCL lines, it may be possible for SCL to fall after SDA during an address or data transfer. Such an event can cause a false START detection on the bus. These kind of events are not expected in a standard SMBus or I2C-compliant system. In most systems this parameter should not be adjusted, and it is recommended that it be left at its default value. By default, if the SCL falling edge is detected after the falling edge of SDA (i.e. one SYSCLK cycle or more), the device will detect this as a START condition. The SMBnSDD field is used to increase the amount of hold time that is required between SDA and SCL falling before a START is recognized. An addi- tional 2, 4, or 8 SYSCLKs can be added to prevent false START detection in systems where the bus condi- tions warrant this. Rev. 1.2 197

C8051F39x/37x SFR Definition 28.1. SMB0CF: SMBus Clock/Configuration Bit 7 6 5 4 3 2 1 0 Name ENSMB0 INH0 BUSY0 EXTHOLD0 SMB0TOE SMB0FTE SMB0CS[1:0] Type R/W R/W R R/W R/W R/W R/W Reset 0 0 0 0 0 0 0 0 SFR Address=0xC1; SFR Page=0 Bit Name Function 7 ENSMB0 SMBus0 Enable. This bit enables the SMBus0 interface when set to 1. When enabled, the interface constantly monitors the SDA0 and SCL0 pins. 6 INH0 SMBus0 Slave Inhibit. When this bit is set to logic 1, the SMBus0 does not generate an interrupt when slave events occur. This effectively removes the SMBus0 slave from the bus. Master Mode interrupts are not affected. 5 BUSY0 SMBus0 Busy Indicator. This bit is set to logic1 by hardware when a transfer is in progress. It is cleared to logic0 when a STOP or free-timeout is sensed. 4 EXTHOLD0 SMBus0 Setup and Hold Time Extension Enable. This bit controls the SDA0 setup and hold times according to Table28.2. 0: SDA0 Extended Setup and Hold Times disabled. 1: SDA0 Extended Setup and Hold Times enabled. 3 SMB0TOE SMBus0 SCL Timeout Detection Enable. This bit enables SCL low timeout detection. If set to logic1, the SMBus0 forces Timer3 to reload while SCL0 is high and allows Timer3 to count when SCL0 goes low. If Timer3 is configured to Split Mode, only the High Byte of the timer is held in reload while SCL0 is high. Timer3 should be programmed to generate interrupts at 25ms, and the Timer3 interrupt service routine should reset SMBus0 communication. 2 SMB0FTE SMBus0 Free Timeout Detection Enable. When this bit is set to logic1, the bus will be considered free if SCL0 and SDA0 remain high for more than 10SMBus clock source peri- ods. 1:0 SMB0CS[1:0] SMBus0 Clock Source Selection. These two bits select the SMBus0 clock source, which is used to generate the SMBus0 bit rate. The selected device should be config- ured according to Equation28.1. 00: Timer 0 Overflow 01: Timer 1 Overflow 10: Timer 2 High Byte Overflow 11: Timer 2 Low Byte Overflow 198 Rev. 1.2

C8051F39x/37x SFR Definition 28.2. SMB1CF: SMBus Clock/Configuration Bit 7 6 5 4 3 2 1 0 Name ENSMB1 INH1 BUSY1 EXTHOLD1 SMB1TOE SMB1FTE SMB1CS[1:0] Type R/W R/W R R/W R/W R/W R/W Reset 0 0 0 0 0 0 0 0 SFR Address=0xC1; SFR Page=F Bit Name Function 7 ENSMB1 SMBus1 Enable. This bit enables the SMBus1 interface when set to 1. When enabled, the interface constantly monitors the SDA1 and SCL1 pins. 6 INH1 SMBus1 Slave Inhibit. When this bit is set to logic 1, the SMBus1 does not generate an interrupt when slave events occur. This effectively removes the SMBus1 slave from the bus. Master Mode interrupts are not affected. 5 BUSY1 SMBus1 Busy Indicator. This bit is set to logic1 by hardware when a transfer is in progress. It is cleared to logic0 when a STOP or free-timeout is sensed. 4 EXTHOLD1 SMBus1 Setup and Hold Time Extension Enable. This bit controls the SDA1 setup and hold times according to Table28.2. 0: SDA1 Extended Setup and Hold Times disabled. 1: SDA1 Extended Setup and Hold Times enabled. 3 SMB1TOE SMBus1 SCL Timeout Detection Enable. This bit enables SCL low timeout detection. If set to logic1, the SMBus1 forces Timer4 to reload while SCL1 is high and allows Timer4 to count when SCL1 goes low. If Timer4 is configured to Split Mode, only the High Byte of the timer is held in reload while SCL1 is high. Timer4 should be programmed to generate interrupts at 25ms, and the Timer4 interrupt service routine should reset SMBus1 communication. 2 SMB1FTE SMBus1 Free Timeout Detection Enable. When this bit is set to logic1, the bus will be considered free if SCL1 and SDA1 remain high for more than 10SMBus clock source peri- ods. 1:0 SMB1CS[1:0] SMBus1 Clock Source Selection. These two bits select the SMBus1 clock source, which is used to generate the SMBus1 bit rate. The selected device should be config- ured according to Equation28.1. 00: Timer 0 Overflow 01: Timer 5 Overflow 10: Timer 2 High Byte Overflow 11: Timer 2 Low Byte Overflow Rev. 1.2 199

C8051F39x/37x SFR Definition 28.3. SMBTC: SMBus Timing and Pin Control Bit 7 6 5 4 3 2 1 0 Name SMB1SWAP SMB0SWAP SMB1SDD[1:0] SMB0SDD[1:0] Type R/W R/W R/W R/W R/W R/W Reset 0 0 0 0 0 0 0 0 SFR Address=0xC7; SFR Page=All Pages Bit Name Function 7 SMB1SWAP SMBus1 Swap Pins This bit swaps the order of the SMBus1 pins on the cross- bar. This should be set to 1 when accessing the EEPROM. 0: SDA1 is mapped to the lower-numbered port pin, and SCL1 is mapped to the higher-numbered port pin. 1: SCL1 is mapped to the lower-numbered port pin, and SDA1 is mapped to the higher-numbered port pin. 6 SMB0SWAP SMBus0 Swap Pins This bit swaps the order of the SMBus1 pins on the cross- bar. This should be set to 1 when accessing the EEPROM. 0: SDA0 is mapped to the lower-numbered port pin, and SCL0 is mapped to the higher-numbered port pin. 1: SCL0 is mapped to the lower-numbered port pin, and SDA0 is mapped to the higher-numbered port pin. 5:4 Reserved Must Write 00b. 3:2 SMB1SDD[1:0] SMBus1 Start Detection Window These bits increase the hold time requirement between SDA falling and SCL falling for START detection. 00: No additional hold time requirement (0-1 SYSCLK). 01: Increase hold time window to 2-3 SYSCLKs. 10: Increase hold time window to 4-5 SYSCLKs. 11: Increase hold time window to 8-9 SYSCLKs. 1:0 SMB0SDD[1:0] SMBus0 Start Detection Window These bits increase the hold time requirement between SDA falling and SCL falling for START detection. 00: No additional hold time window (0-1 SYSCLK). 01: Increase hold time window to 2-3 SYSCLKs. 10: Increase hold time window to 4-5 SYSCLKs. 11: Increase hold time window to 8-9 SYSCLKs. 200 Rev. 1.2

C8051F39x/37x 28.4.4. SMBnCN Control Register SMBnCN is used to control the interface and to provide status information (see SFR Definition 28.4). The higher four bits of SMBnCN (MASTER, TXMODE, STA, and STO) form a status vector that can be used to jump to service routines. MASTER indicates whether a device is the master or slave during the current transfer. TXMODE indicates whether the device is transmitting or receiving data for the current byte. STA and STO indicate that a START and/or STOP has been detected or generated since the last SMBus interrupt. STA and STO are also used to generate START and STOP conditions when operating as a mas- ter. Writing a 1 to STA will cause the SMBus interface to enter Master Mode and generate a START when the bus becomes free (STA is not cleared by hardware after the START is generated). Writing a 1 to STO while in Master Mode will cause the interface to generate a STOP and end the current transfer after the next ACK cycle. If STO and STA are both set (while in Master Mode), a STOP followed by a START will be generated. The ARBLOST bit indicates that the interface has lost an arbitration. This may occur anytime the interface is transmitting (master or slave). A lost arbitration while operating as a slave indicates a bus error condi- tion. ARBLOST is cleared by hardware each time SI is cleared. The SI bit (SMBus Interrupt Flag) is set at the beginning and end of each transfer, after each byte frame, or when an arbitration is lost; see Table28.3 for more details. Important Note About the SI Bit: The SMBus interface is stalled while SI is set; thus SCL is held low, and the bus is stalled until software clears SI. 28.4.4.1. Software ACK Generation When the EHACK bit in register SMBnADM is cleared to 0, the firmware on the device must detect incom- ing slave addresses and ACK or NACK the slave address and incoming data bytes. As a receiver, writing the ACK bit defines the outgoing ACK value; as a transmitter, reading the ACK bit indicates the value received during the last ACK cycle. ACKRQ is set each time a byte is received, indicating that an outgoing ACK value is needed. When ACKRQ is set, software should write the desired outgoing value to the ACK bit before clearing SI. A NACK will be generated if software does not write the ACK bit before clearing SI. SDA will reflect the defined ACK value immediately following a write to the ACK bit; however SCL will remain low until SI is cleared. If a received slave address is not acknowledged, further slave events will be ignored until the next START is detected. 28.4.4.2. Hardware ACK Generation When the EHACK bit in register SMB0ADM is set to 1, automatic slave address recognition and ACK gen- eration is enabled. More detail about automatic slave address recognition can be found in Section 28.4.5. As a receiver, the value currently specified by the ACK bit will be automatically sent on the bus during the ACK cycle of an incoming data byte. As a transmitter, reading the ACK bit indicates the value received on the last ACK cycle. The ACKRQ bit is not used when hardware ACK generation is enabled. If a received slave address is NACKed by hardware, further slave events will be ignored until the next START is detected, and no interrupt will be generated. Table28.3 lists all sources for hardware changes to the SMBnCN bits. Refer to Table28.5 for SMBus sta- tus decoding using the SMBnCN register. Rev. 1.2 201

C8051F39x/37x SFR Definition 28.4. SMB0CN: SMBus Control Bit 7 6 5 4 3 2 1 0 Name MASTER0 TXMODE0 STA0 STO0 ACKRQ0 ARBLOST0 ACK0 SI0 Type R R R/W R/W R R R/W R/W Reset 0 0 0 0 0 0 0 0 SFR Address=0xC0; SFR Page=0; Bit-Addressable Bit Name Description Read Write 7 MASTER0 SMBus0 Master/Slave 0: SMBus0 operating in N/A Indicator. This read-only bit slave mode. indicates when the SMBus0 is 1: SMBus0 operating in operating as a master. master mode. 6 TXMODE0 SMBus0 Transmit Mode 0: SMBus0 in Receiver N/A Indicator. This read-only bit Mode. indicates when the SMBus0 is 1: SMBus0 in Transmitter operating as a transmitter. Mode. 5 STA0 SMBus0 Start Flag. 0: No Start or repeated 0: No Start generated. Start detected. 1: When Configured as a 1: Start or repeated Start Master, initiates a START detected. or repeated START. 4 STO0 SMBus0 Stop Flag. 0: No Stop condition 0: No STOP condition is detected. transmitted. 1: Stop condition detected 1: When configured as a (if in Slave Mode) or Master, causes a STOP pending (if in Master condition to be transmit- Mode). ted after the next ACK cycle. Cleared by Hardware. 3 ACKRQ0 SMBus0 Acknowledge 0: No ACK requested N/A Request. 1: ACK requested 2 ARBLOST0 SMBus0 Arbitration Lost 0: No arbitration error. N/A Indicator. 1: Arbitration Lost 1 ACK0 SMBus0 Acknowledge. 0: NACK received. 0: Send NACK 1: ACK received. 1: Send ACK 0 SI0 SMBus0 Interrupt Flag. 0: No interrupt pending 0: Clear interrupt, and ini- This bit is set by hardware 1: Interrupt Pending tiate next state machine under the conditions listed in event. Table28.3. SI0 must be 1: Force interrupt. cleared by software. While SI0 is set, SCL0 is held low and the SMBus0 is stalled. 202 Rev. 1.2

C8051F39x/37x SFR Definition 28.5. SMB1CN: SMBus Control Bit 7 6 5 4 3 2 1 0 Name MASTER1 TXMODE1 STA1 STO1 ACKRQ1 ARBLOST1 ACK1 SI1 Type R R R/W R/W R R R/W R/W Reset 0 0 0 0 0 0 0 0 SFR Address=0xC0; SFR Page=F; Bit-Addressable Bit Name Description Read Write 7 MASTER1 SMBus1 Master/Slave 0: SMBus1 operating in N/A Indicator. This read-only bit slave mode. indicates when the SMBus1 is 1: SMBus1 operating in operating as a master. master mode. 6 TXMODE1 SMBus1 Transmit Mode 0: SMBus1 in Receiver N/A Indicator. This read-only bit Mode. indicates when the SMBus1 is 1: SMBus1 in Transmitter operating as a transmitter. Mode. 5 STA1 SMBus1 Start Flag. 0: No Start or repeated 0: No Start generated. Start detected. 1: When Configured as a 1: Start or repeated Start Master, initiates a START detected. or repeated START. 4 STO1 SMBus1 Stop Flag. 0: No Stop condition 0: No STOP condition is detected. transmitted. 1: Stop condition detected 1: When configured as a (if in Slave Mode) or Master, causes a STOP pending (if in Master condition to be transmit- Mode). ted after the next ACK cycle. Cleared by Hardware. 3 ACKRQ1 SMBus1 Acknowledge 0: No ACK requested N/A Request. 1: ACK requested 2 ARBLOST1 SMBus1 Arbitration Lost 0: No arbitration error. N/A Indicator. 1: Arbitration Lost 1 ACK1 SMBus1 Acknowledge. 0: NACK received. 0: Send NACK 1: ACK received. 1: Send ACK 0 SI1 SMBus1 Interrupt Flag. 0: No interrupt pending 0: Clear interrupt, and ini- This bit is set by hardware 1: Interrupt Pending tiate next state machine under the conditions listed in event. Table28.3. SI1 must be 1: Force interrupt. cleared by software. While SI1 is set, SCL1 is held low and the SMBus1 is stalled. Rev. 1.2 203

C8051F39x/37x Table 28.3. Sources for Hardware Changes to SMBnCN Bit Set by Hardware When: Cleared by Hardware When:  A START is generated.  A STOP is generated. MASTERn  Arbitration is lost.  START is generated.  A START is detected.  SMBnDAT is written before the start of an  Arbitration is lost1. TXMODEn SMBus frame.  SMBnDAT is not written before the start of an SMBus frame.  A START followed by an address byte is  Must be cleared by software. STAn received.  A STOP is detected while addressed as a  A pending STOP is generated. STOn slave.  Arbitration is lost due to a detected STOP.  A byte has been received and an ACK  After each ACK cycle. ACKRQn response value is needed (only when hardware ACK is not enabled).  A repeated START is detected as a  Each time SIn is cleared. MASTER when STAn is low (unwanted repeated START).  SCLn is sensed low while attempting to ARBLOSTn generate a STOP or repeated START condition.  SDAn is sensed low while transmitting a 1 (excluding ACK bits).  The incoming ACK value is low  The incoming ACK value is high ACKn (ACKNOWLEDGE). (NOT ACKNOWLEDGE).  A START has been generated.  Must be cleared by software.  Lost arbitration.  A byte has been transmitted and an ACK/ NACK received. SIn  A byte has been received.  A START or repeated START followed by a slave address + R/W has been received.  A STOP has been received. Notes: 1. When arbitration is lost, hardware clears TXMODEn after software clears SIn. 28.4.5. Hardware Slave Address Recognition The SMBus hardware has the capability to automatically recognize incoming slave addresses and send an ACK without software intervention. Automatic slave address recognition is enabled by setting the EHACK bit in register SMB0ADM to 1. This will enable both automatic slave address recognition and automatic hardware ACK generation for received bytes (as a master or slave). More detail on automatic hardware ACK generation can be found in Section 28.4.4.2. The registers used to define which address(es) are recognized by the hardware are the SMBus Slave Address register and the SMBus Slave Address Mask register. A single address or range of addresses (including the General Call Address 0x00) can be specified using these two registers. The most-significant seven bits of the two registers are used to define which addresses will be ACKed. A 1 in bit positions of the 204 Rev. 1.2

C8051F39x/37x slave address mask SLVM[6:0] enable a comparison between the received slave address and the hard- ware’s slave address SLV[6:0] for those bits. A 0 in a bit of the slave address mask means that bit will be treated as a “don’t care” for comparison purposes. In this case, either a 1 or a 0 value are acceptable on the incoming slave address. Additionally, if the GCn bit in register SMBnADR is set to 1, hardware will rec- ognize the General Call Address (0x00). Table28.4 shows some example parameter settings and the slave addresses that will be recognized by hardware under those conditions. Table 28.4. Hardware Address Recognition Examples (EHACK = 1) Hardware Slave Address Slave Address Mask GCn bit Slave Addresses Recognized by SLVn[6:0] SLVMn[6:0] Hardware 0x34 0x7F 0 0x34 0x34 0x7F 1 0x34, 0x00 (General Call) 0x34 0x7E 0 0x34, 0x35 0x34 0x7E 1 0x34, 0x35, 0x00 (General Call) 0x70 0x73 0 0x70, 0x74, 0x78, 0x7C SFR Definition 28.6. SMB0ADR: SMBus0 Slave Address Bit 7 6 5 4 3 2 1 0 Name SLV0[6:0] GC0 Type R/W R/W Reset 0 0 0 0 0 0 0 0 SFR Address=0xD7; SFR Page=0 Bit Name Function 7:1 SLV0[6:0] SMBus Hardware Slave Address. Defines the SMBus0 Slave Address(es) for automatic hardware acknowledgment. Only address bits which have a 1 in the corresponding bit position in SLVM0[6:0] are checked against the incoming address. This allows multi- ple addresses to be recognized. 0 GC0 General Call Address Enable. When hardware address recognition is enabled (EHACK0=1), this bit will determine whether the General Call Address (0x00) is also recognized by hardware. 0: General Call Address is ignored. 1: General Call Address is recognized. Rev. 1.2 205

C8051F39x/37x SFR Definition 28.7. SMB0ADM: SMBus0 Slave Address Mask Bit 7 6 5 4 3 2 1 0 Name SLVM0[6:0] EHACK0 Type R/W R/W Reset 1 1 1 1 1 1 1 0 SFR Address=0xE7; SFR Page=0 Bit Name Function 7:1 SLVM0[6:0] SMBus0 Slave Address Mask. Defines which bits of register SMB0ADR are compared with an incoming address byte, and which bits are ignored. Any bit set to 1 in SLVM0[6:0] enables comparisons with the corresponding bit in SLV0[6:0]. Bits set to 0 are ignored (can be either 0 or 1 in the incoming address). 0 EHACK0 Hardware Acknowledge Enable. Enables hardware acknowledgement of slave address and received data bytes. 0: Firmware must manually acknowledge all incoming address and data bytes. 1: Automatic Slave Address Recognition and Hardware Acknowledge is Enabled. 206 Rev. 1.2

C8051F39x/37x SFR Definition 28.8. SMB1ADR: SMBus1 Slave Address Bit 7 6 5 4 3 2 1 0 Name SLV1[6:0] GC1 Type R/W R/W Reset 0 0 0 0 0 0 0 0 SFR Address=0xD7; SFR Page=F Bit Name Function 7:1 SLV1[6:0] SMBus1 Hardware Slave Address. Defines the SMBus1 Slave Address(es) for automatic hardware acknowledgment. Only address bits which have a 1 in the corresponding bit position in SLVM1[6:0] are checked against the incoming address. This allows multi- ple addresses to be recognized. 0 GC1 General Call Address Enable. When hardware address recognition is enabled (EHACK1=1), this bit will determine whether the General Call Address (0x00) is also recognized by hardware. 0: General Call Address is ignored. 1: General Call Address is recognized. Rev. 1.2 207

C8051F39x/37x SFR Definition 28.9. SMB1ADM: SMBus1 Slave Address Mask Bit 7 6 5 4 3 2 1 0 Name SLVM1[6:0] EHACK1 Type R/W R/W Reset 1 1 1 1 1 1 1 0 SFR Address=0xE7; SFR Page=F Bit Name Function 7:1 SLVM1[6:0] SMBus1 Slave Address Mask. Defines which bits of register SMB1ADR are compared with an incoming address byte, and which bits are ignored. Any bit set to 1 in SLVM1[6:0] enables comparisons with the corresponding bit in SLV1[6:0]. Bits set to 0 are ignored (can be either 0 or 1 in the incoming address). 0 EHACK1 Hardware Acknowledge Enable. Enables hardware acknowledgement of slave address and received data bytes. 0: Firmware must manually acknowledge all incoming address and data bytes. 1: Automatic Slave Address Recognition and Hardware Acknowledge is Enabled. 208 Rev. 1.2

C8051F39x/37x 28.4.6. Data Register The SMBus Data register SMBnDAT holds a byte of serial data to be transmitted or one that has just been received. Software may safely read or write to the data register when the SIn flag is set. Software should not attempt to access the SMBnDAT register when the SMBus is enabled and the SIn flag is cleared to logic0, as the interface may be in the process of shifting a byte of data into or out of the register. Data in SMBnDAT is always shifted out MSB first. After a byte has been received, the first bit of received data is located at the MSB of SMBnDAT. While data is being shifted out, data on the bus is simultaneously being shifted in. SMBnDAT always contains the last data byte present on the bus. In the event of lost arbi- tration, the transition from master transmitter to slave receiver is made with the correct data or address in SMBnDAT. SFR Definition 28.10. SMB0DAT: SMBus Data Bit 7 6 5 4 3 2 1 0 Name SMB0DAT[7:0] Type R/W Reset 0 0 0 0 0 0 0 0 SFR Address=0xC2; SFR Page=0 Bit Name Function 7:0 SMB0DAT[7:0] SMBus0 Data. The SMB0DAT register contains a byte of data to be trans- mitted on the SMBus0 serial interface or a byte that has just been received on the SMBus0 serial interface. The CPU can read from or write to this register whenever the SI0 serial interrupt flag (SMB0CN.0) is set to logic1. The serial data in the register remains stable as long as the SI0 flag is set. When the SI0 flag is not set, the system may be in the process of shifting data in/out and the CPU should not attempt to access this register. Rev. 1.2 209

C8051F39x/37x SFR Definition 28.11. SMB1DAT: SMBus Data Bit 7 6 5 4 3 2 1 0 Name SMB1DAT[7:0] Type R/W Reset 0 0 0 0 0 0 0 0 SFR Address=0xC2; SFR Page=F Bit Name Function 7:0 SMB1DAT[7:0] SMBus1 Data. The SMB1DAT register contains a byte of data to be trans- mitted on the SMBus1 serial interface or a byte that has just been received on the SMBus1 serial interface. The CPU can read from or write to this register whenever the SI1 serial interrupt flag (SMB1CN.0) is set to logic1. The serial data in the register remains stable as long as the SI1 flag is set. When the SI1 flag is not set, the system may be in the process of shifting data in/out and the CPU should not attempt to access this register. 210 Rev. 1.2

C8051F39x/37x 28.5. SMBus Transfer Modes The SMBus interface may be configured to operate as master and/or slave. At any particular time, it will be operating in one of the following four modes: Master Transmitter, Master Receiver, Slave Transmitter, or Slave Receiver. The SMBus interface enters Master Mode any time a START is generated, and remains in Master Mode until it loses an arbitration or generates a STOP. An SMBus interrupt is generated at the end of all SMBus byte frames. The position of the ACK interrupt when operating as a receiver depends on whether hardware ACK generation is enabled. As a receiver, the interrupt for an ACK occurs before the ACK with hardware ACK generation disabled, and after the ACK when hardware ACK generation is enabled. As a transmitter, interrupts occur after the ACK, regardless of whether hardware ACK generation is enabled or not. 28.5.1. Write Sequence (Master) During a write sequence, an SMBus master writes data to a slave device. The master in this transfer will be a transmitter during the address byte, and a transmitter during all data bytes. The SMBus interface gener- ates the START condition and transmits the first byte containing the address of the target slave and the data direction bit. In this case the data direction bit (R/W) will be logic0 (WRITE). The master then trans- mits one or more bytes of serial data. After each byte is transmitted, an acknowledge bit is generated by the slave. The transfer is ended when the STO bit is set and a STOP is generated. The interface will switch to Master Receiver Mode if SMB0DAT is not written following a Master Transmitter interrupt. Figure28.5 shows a typical master write sequence. Two transmit data bytes are shown, though any number of bytes may be transmitted. Notice that all of the “data byte transferred” interrupts occur after the ACK cycle in this mode, regardless of whether hardware ACK generation is enabled. Interrupts with Hardware ACK Enabled (EHACK = 1) S SLA W A Data Byte A Data Byte A P Interrupts with Hardware ACK Disabled (EHACK = 0) Received by SMBus S = START Interface P = STOP A = ACK Transmitted by W = WRITE SMBus Interface SLA = Slave Address Figure 28.5. Typical Master Write Sequence Rev. 1.2 211

C8051F39x/37x 28.5.2. Read Sequence (Master) During a read sequence, an SMBus master reads data from a slave device. The master in this transfer will be a transmitter during the address byte, and a receiver during all data bytes. The SMBus interface gener- ates the START condition and transmits the first byte containing the address of the target slave and the data direction bit. In this case the data direction bit (R/W) will be logic1 (READ). Serial data is then received from the slave on SDA while the SMBus outputs the serial clock. The slave transmits one or more bytes of serial data. If hardware ACK generation is disabled, the ACKRQ is set to 1 and an interrupt is generated after each received byte. Software must write the ACK bit at that time to ACK or NACK the received byte. With hardware ACK generation enabled, the SMBus hardware will automatically generate the ACK/NACK, and then post the interrupt. It is important to note that the appropriate ACK or NACK value should be set up by the software prior to receiving the byte when hardware ACK generation is enabled. Writing a 1 to the ACK bit generates an ACK; writing a 0 generates a NACK. Software should write a 0 to the ACK bit for the last data transfer, to transmit a NACK. The interface exits Master Receiver Mode after the STO bit is set and a STOP is generated. The interface will switch to Master Transmitter Mode if SMB0- DAT is written while an active Master Receiver. Figure28.6 shows a typical master read sequence. Two received data bytes are shown, though any number of bytes may be received. Notice that the ‘data byte transferred’ interrupts occur at different places in the sequence, depending on whether hardware ACK gen- eration is enabled. The interrupt occurs before the ACK with hardware ACK generation disabled, and after the ACK when hardware ACK generation is enabled. Interrupts with Hardware ACK Enabled (EHACK = 1) S SLA R A Data Byte A Data Byte N P Interrupts with Hardware ACK Disabled (EHACK = 0) Received by SMBus S = START Interface P = STOP A = ACK N = NACK Transmitted by R = READ SMBus Interface SLA = Slave Address Figure 28.6. Typical Master Read Sequence 212 Rev. 1.2

C8051F39x/37x 28.5.3. Write Sequence (Slave) During a write sequence, an SMBus master writes data to a slave device. The slave in this transfer will be a receiver during the address byte, and a receiver during all data bytes. When slave events are enabled (INH=0), the interface enters Slave Receiver Mode when a START followed by a slave address and direc- tion bit (WRITE in this case) is received. If hardware ACK generation is disabled, upon entering Slave Receiver Mode, an interrupt is generated and the ACKRQ bit is set. The software must respond to the received slave address with an ACK, or ignore the received slave address with a NACK. If hardware ACK generation is enabled, the hardware will apply the ACK for a slave address which matches the criteria set up by SMB0ADR and SMB0ADM. The interrupt will occur after the ACK cycle. If the received slave address is ignored (by software or hardware), slave interrupts will be inhibited until the next START is detected. If the received slave address is acknowledged, zero or more data bytes are received. If hardware ACK generation is disabled, the ACKRQ is set to 1 and an interrupt is generated after each received byte. Software must write the ACK bit at that time to ACK or NACK the received byte. With hardware ACK generation enabled, the SMBus hardware will automatically generate the ACK/NACK, and then post the interrupt. It is important to note that the appropriate ACK or NACK value should be set up by the software prior to receiving the byte when hardware ACK generation is enabled. The interface exits Slave Receiver Mode after receiving a STOP. The interface will switch to Slave Trans- mitter Mode if SMB0DAT is written while an active Slave Receiver. Figure28.7 shows a typical slave write sequence. Two received data bytes are shown, though any number of bytes may be received. Notice that the ‘data byte transferred’ interrupts occur at different places in the sequence, depending on whether hard- ware ACK generation is enabled. The interrupt occurs before the ACK with hardware ACK generation dis- abled, and after the ACK when hardware ACK generation is enabled. Interrupts with Hardware ACK Enabled (EHACK = 1) S SLA W A Data Byte A Data Byte A P Interrupts with Hardware ACK Disabled (EHACK = 0) Received by SMBus S = START Interface P = STOP A = ACK W = WRITE Transmitted by SLA = Slave Address SMBus Interface Figure 28.7. Typical Slave Write Sequence Rev. 1.2 213

C8051F39x/37x 28.5.4. Read Sequence (Slave) During a read sequence, an SMBus master reads data from a slave device. The slave in this transfer will be a receiver during the address byte, and a transmitter during all data bytes. When slave events are enabled (INH=0), the interface enters Slave Receiver Mode (to receive the slave address) when a START followed by a slave address and direction bit (READ in this case) is received. If hardware ACK generation is disabled, upon entering Slave Receiver Mode, an interrupt is generated and the ACKRQ bit is set. The software must respond to the received slave address with an ACK, or ignore the received slave address with a NACK. If hardware ACK generation is enabled, the hardware will apply the ACK for a slave address which matches the criteria set up by SMB0ADR and SMB0ADM. The interrupt will occur after the ACK cycle. If the received slave address is ignored (by software or hardware), slave interrupts will be inhibited until the next START is detected. If the received slave address is acknowledged, zero or more data bytes are trans- mitted. If the received slave address is acknowledged, data should be written to SMB0DAT to be transmit- ted. The interface enters slave transmitter mode, and transmits one or more bytes of data. After each byte is transmitted, the master sends an acknowledge bit; if the acknowledge bit is an ACK, SMB0DAT should be written with the next data byte. If the acknowledge bit is a NACK, SMB0DAT should not be written to before SI is cleared (an error condition may be generated if SMB0DAT is written following a received NACK while in slave transmitter mode). The interface exits slave transmitter mode after receiving a STOP. The interface will switch to slave receiver mode if SMB0DAT is not written following a Slave Transmitter interrupt. Figure28.8 shows a typical slave read sequence. Two transmitted data bytes are shown, though any number of bytes may be transmitted. Notice that all of the “data byte transferred” interrupts occur after the ACK cycle in this mode, regardless of whether hardware ACK generation is enabled. Interrupts with Hardware ACK Enabled (EHACK = 1) S SLA R A Data Byte A Data Byte N P Interrupts with Hardware ACK Disabled (EHACK = 0) Received by SMBus S = START Interface P = STOP N = NACK R = READ Transmitted by SLA = Slave Address SMBus Interface Figure 28.8. Typical Slave Read Sequence 28.6. SMBus Status Decoding The current SMBus status can be easily decoded using the SMB0CN register. The appropriate actions to take in response to an SMBus event depend on whether hardware slave address recognition and ACK generation is enabled or disabled. Table28.5 describes the typical actions when hardware slave address recognition and ACK generation is disabled. Table28.6 describes the typical actions when hardware slave address recognition and ACK generation is enabled. In the tables, STATUS VECTOR refers to the four upper bits of SMB0CN: MASTER, TXMODE, STA, and STO. The shown response options are only the typ- ical responses; application-specific procedures are allowed as long as they conform to the SMBus specifi- cation. Highlighted responses are allowed by hardware but do not conform to the SMBus specification. 214 Rev. 1.2

C8051F39x/37x Table 28.5. SMBus Status Decoding: Hardware ACK Disabled (EHACK = 0) Values to d Values Read e Write us ct e at pe Mod Status Vector ACKRQ RBLOST ACK Current SMbus State Typical Response Options STA STO ACK Next St ector Ex A V A master START was gener- Load slave address + R/W into 0 0 X 1100 1110 0 0 X ated. SMB0DAT. A master data or address byte Set STA to restart transfer. 1 0 X 1110 0 0 0 was transmitted; NACK received. Abort transfer. 0 1 X — r e t mit Load next data byte into SMB0- 0 0 X 1100 s DAT. n a r End transfer with STOP. 0 1 X — T r 1100 e A master data or address byte End transfer with STOP and start 1 1 X — t s a 0 0 1 was transmitted; ACK another transfer. M received. Send repeated START. 1 0 X 1110 Switch to Master Receiver Mode 0 0 X 1000 (clear SI without writing new data to SMB0DAT). Acknowledge received byte; 0 0 1 1000 Read SMB0DAT. Send NACK to indicate last byte, 0 1 0 — and send STOP. Send NACK to indicate last byte, 1 1 0 1110 and send STOP followed by er START. v ei Send ACK followed by repeated 1 0 1 1110 ec A master data byte was R 1000 1 0 X START. received; ACK requested. r e Send NACK to indicate last byte, 1 0 0 1110 t s a and send repeated START. M Send ACK and switch to Master 0 0 1 1100 Transmitter Mode (write to SMB0DAT before clearing SI). Send NACK and switch to Mas- 0 0 0 1100 ter Transmitter Mode (write to SMB0DAT before clearing SI). Rev. 1.2 215

C8051F39x/37x Table 28.5. SMBus Status Decoding: Hardware ACK Disabled (EHACK = 0) (Continued) Values to d Values Read e Write us ct e at pe Mod Status Vector ACKRQ RBLOST ACK Current SMbus State Typical Response Options STA STO ACK Next St ector Ex A V A slave byte was transmitted; No action required (expecting 0 0 X 0001 0 0 0 NACK received. STOP condition). r e t A slave byte was transmitted; Load SMB0DAT with next data 0 0 X 0100 mit 0100 0 0 1 ACK received. byte to transmit. s n a A Slave byte was transmitted; No action required (expecting 0 0 X 0001 r 0 1 X T error detected. Master to end transfer). e v a An illegal STOP or bus error 0 0 X — Sl 0101 0 X X was detected while a Slave Clear STO. Transmission was in progress. If Write, Acknowledge received 0 0 1 0000 address A slave address + R/W was 1 0 X If Read, Load SMB0DAT with 0 0 1 0100 received; ACK requested. data byte; ACK received address NACK received address. 0 0 0 — If Write, Acknowledge received 0 0 1 0000 0010 address If Read, Load SMB0DAT with 0 0 1 0100 Lost arbitration as master; r e data byte; ACK received address v 1 1 X slave address + R/W received; cei ACK requested. NACK received address. 0 0 0 — e R e Reschedule failed transfer; 1 0 0 1110 v a NACK received address. Sl A STOP was detected while 0 0 X — 0 0 X addressed as a Slave Trans- Clear STO. 0001 mitter or Slave Receiver. Lost arbitration while attempt- No action required (transfer 0 0 0 — 1 1 X ing a STOP. complete/aborted). Acknowledge received byte; 0 0 1 0000 0000 1 0 X A slave byte was received; Read SMB0DAT. ACK requested. NACK received byte. 0 0 0 — 216 Rev. 1.2

C8051F39x/37x Table 28.5. SMBus Status Decoding: Hardware ACK Disabled (EHACK = 0) (Continued) Values to d Values Read e Write us ct e at pe Mod Status Vector ACKRQ RBLOST ACK Current SMbus State Typical Response Options STA STO ACK Next St ector Ex A V n Lost arbitration while attempt- Abort failed transfer. 0 0 X — o 0010 0 1 X ti ing a repeated START. Reschedule failed transfer. 1 0 X 1110 di n o Lost arbitration due to a Abort failed transfer. 0 0 X — C 0001 0 1 X or detected STOP. Reschedule failed transfer. 1 0 X 1110 r r s E 0000 1 1 X Lost arbitration while transmit- Abort failed transfer. 0 0 0 — Bu ting a data byte as master. Reschedule failed transfer. 1 0 0 1110 Table 28.6. SMBus Status Decoding: Hardware ACK Enabled (EHACK = 1) Values to d Values Read e Write us ct e at pe Mod Status Vector ACKRQ RBLOST ACK Current SMbus State Typical Response Options STA STO ACK Next St ector Ex A V A master START was gener- Load slave address + R/W into 0 0 X 1100 1110 0 0 X ated. SMB0DAT. A master data or address byte Set STA to restart transfer. 1 0 X 1110 0 0 0 was transmitted; NACK 0 1 X — Abort transfer. received. r e tt Load next data byte into SMB0- 0 0 X 1100 mi DAT. s n a End transfer with STOP. 0 1 X — r T r 1100 End transfer with STOP and start 1 1 X — e A master data or address byte t another transfer. s 0 0 1 was transmitted; ACK a M received. Send repeated START. 1 0 X 1110 Switch to Master Receiver Mode 0 0 1 1000 (clear SI without writing new data to SMB0DAT). Set ACK for initial data byte. Rev. 1.2 217

C8051F39x/37x Table 28.6. SMBus Status Decoding: Hardware ACK Enabled (EHACK = 1) (Continued) Values to d Values Read e Write us ct e at pe Mod Status Vector ACKRQ RBLOST ACK Current SMbus State Typical Response Options STA STO ACK Next St ector Ex A V Set ACK for next data byte; 0 0 1 1000 Read SMB0DAT. Set NACK to indicate next data 0 0 0 1000 byte as the last data byte; A master data byte was 0 0 1 Read SMB0DAT. received; ACK sent. r Initiate repeated START. 1 0 0 1110 e v ei Switch to Master Transmitter 0 0 X 1100 c Mode (write to SMB0DAT before e R 1000 clearing SI). r e t Read SMB0DAT; send STOP. 0 1 0 — s a M Read SMB0DAT; Send STOP 1 1 0 1110 A master data byte was followed by START. 0 0 0 received; NACK sent (last Initiate repeated START. 1 0 0 1110 byte). Switch to Master Transmitter 0 0 X 1100 Mode (write to SMB0DAT before clearing SI). A slave byte was transmitted; No action required (expecting 0 0 X 0001 0 0 0 NACK received. STOP condition). r e t A slave byte was transmitted; Load SMB0DAT with next data 0 0 X 0100 mit 0100 0 0 1 ACK received. byte to transmit. s n a A Slave byte was transmitted; No action required (expecting 0 0 X 0001 r 0 1 X T error detected. Master to end transfer). e av An illegal STOP or bus error 0 0 X — Sl 0101 0 X X was detected while a Slave Clear STO. Transmission was in progress. 218 Rev. 1.2

C8051F39x/37x Table 28.6. SMBus Status Decoding: Hardware ACK Enabled (EHACK = 1) (Continued) Values to d Values Read e Write us ct e at pe Mod Status Vector ACKRQ RBLOST ACK Current SMbus State Typical Response Options STA STO ACK Next St ector Ex A V If Write, Set ACK for first data 0 0 1 0000 A slave address + R/W was byte. 0 0 X received; ACK sent. If Read, Load SMB0DAT with 0 0 X 0100 data byte 0010 If Write, Set ACK for first data 0 0 1 0000 byte. Lost arbitration as master; 0 1 X slave address + R/W received; If Read, Load SMB0DAT with 0 0 X 0100 r e ACK sent. data byte v ei c Reschedule failed transfer 1 0 X 1110 e R A STOP was detected while 0 0 X — e v 0 0 X addressed as a Slave Trans- Clear STO. a Sl 0001 mitter or Slave Receiver. Lost arbitration while attempt- No action required (transfer 0 0 0 — 0 1 X ing a STOP. complete/aborted). Set ACK for next data byte; 0 0 1 0000 Read SMB0DAT. 0000 0 0 X A slave byte was received. Set NACK for next data byte; 0 0 0 0000 Read SMB0DAT. n Lost arbitration while attempt- Abort failed transfer. 0 0 X — o 0010 0 1 X diti ing a repeated START. Reschedule failed transfer. 1 0 X 1110 n o Lost arbitration due to a Abort failed transfer. 0 0 X — C 0001 0 1 X r detected STOP. Reschedule failed transfer. 1 0 X 1110 o r r Abort failed transfer. 0 0 X — E Lost arbitration while transmit- us 0000 0 1 X ting a data byte as master. Reschedule failed transfer. 1 0 X 1110 B Rev. 1.2 219

C8051F39x/37x 29. UART0 UART0 is an asynchronous, full duplex serial port offering modes1 and 3 of the standard 8051 UART. Enhanced baud rate support allows a wide range of clock sources to generate standard baud rates (details in Section “29.1.Enhanced Baud Rate Generation” on page221). Received data buffering allows UART0 to start reception of a second incoming data byte before software has finished reading the previous data byte. UART0 has two associated SFRs: Serial Control Register 0 (SCON0) and Serial Data Buffer 0 (SBUF0). The single SBUF0 location provides access to both transmit and receive registers. Writes to SBUF0 always access the Transmit register. Reads of SBUF0 always access the buffered Receive register; it is not possible to read data from the Transmit register. With UART0 interrupts enabled, an interrupt is generated each time a transmit is completed (TI0 is set in SCON0), or a data byte has been received (RI0 is set in SCON0). The UART0 interrupt flags are not cleared by hardware when the CPU vectors to the interrupt service routine. They must be cleared manually by software, allowing software to determine the cause of the UART0 interrupt (transmit complete or receive complete). SFR Bus Write to SBUF TB8 SBUF DSETQ (TX Shift) TX CLR Crossbar Zero Detector Stop Bit Shift Data Start Tx Control Tx Clock Tx IRQ Send SCON RaUtAe RGTe nBearuadto r MODE MCERENTB8RB8TIRI RTII InStPeeorrriruat plt Port I/O S Rx IRQ Rx Clock Rx Control Start Shift 0x1FF RB8 SLBoaUdF Input Shift Register (9 bits) Load SBUF SBUF (RX Latch) Read SBUF SFR Bus RX Crossbar Figure 29.1. UART0 Block Diagram 220 Rev. 1.2

C8051F39x/37x 29.1. Enhanced Baud Rate Generation The UART0 baud rate is generated by Timer1 in 8-bit auto-reload mode. The TX clock is generated by TL1; the RX clock is generated by a copy of TL1 (shown as RX Timer in Figure29.2), which is not user- accessible. Both TX and RX Timer overflows are divided by two to generate the TX and RX baud rates. The RX Timer runs when Timer1 is enabled, and uses the same reload value (TH1). However, an RXTimer reload is forced when a START condition is detected on the RX pin. This allows a receive to begin any time a START is detected, independent of the TXTimer state. Timer 1 UART Overflow TL1 2 TX Clock TH1 Start Detected Overflow RX Timer 2 RX Clock Figure 29.2. UART0 Baud Rate Logic Timer1 should be configured for Mode2, 8-bit auto-reload (see Section “31.1.3.Mode 2: 8-bit Counter/ Timer with Auto-Reload” on page247). The Timer1 reload value should be set so that overflows will occur at two times the desired UART baud rate frequency. Note that Timer1 may be clocked by one of six sources: SYSCLK, SYSCLK/4, SYSCLK/12, SYSCLK/48, the external oscillator clock/8, or an external input T1. For any given Timer1 clock source, the UART0 baud rate is determined by Equation29.1-A and Equation29.1-B. 1 A) UartBaudRate = --- T1_Overflow_Rate 2 T1 B) T1_Overflow_Rate = ------------C---L---K-------- 256– TH1 Equation 29.1. UART0 Baud Rate Where T1 is the frequency of the clock supplied to Timer1, and T1H is the high byte of Timer 1 (reload CLK value). Timer1 clock frequency is selected as described in Section “31.Timers” on page242. A quick ref- erence for typical baud rates and system clock frequencies is given in Table29.1 through Table29.2. The internal oscillator may still generate the system clock when the external oscillator is driving Timer1. Rev. 1.2 221

C8051F39x/37x 29.2. Operational Modes UART0 provides standard asynchronous, full duplex communication. The UART mode (8-bit or 9-bit) is selected by the S0MODE bit (SCON0.7). Typical UART connection options are shown in Figure29.3. TX RS-232 RS-232 LEVEL RX C8051xxxx XLTR OR TX TX MCU C8051xxxx RX RX Figure 29.3. UART Interconnect Diagram 29.2.1. 8-Bit UART 8-Bit UART mode uses a total of 10bits per data byte: one start bit, eight data bits (LSB first), and one stop bit. Data are transmitted LSB first from the TX0 pin and received at the RX0 pin. On receive, the eight data bits are stored in SBUF0 and the stop bit goes into RB80 (SCON0.2). Data transmission begins when software writes a data byte to the SBUF0 register. The TI0 Transmit Inter- rupt Flag (SCON0.1) is set at the end of the transmission (the beginning of the stop-bit time). Data recep- tion can begin any time after the REN0 Receive Enable bit (SCON0.4) is set to logic1. After the stop bit is received, the data byte will be loaded into the SBUF0 receive register if the following conditions are met: RI0 must be logic0, and if MCE0 is logic1, the stop bit must be logic1. In the event of a receive data over- run, the first received 8bits are latched into the SBUF0 receive register and the following overrun data bits are lost. If these conditions are met, the eight bits of data is stored in SBUF0, the stop bit is stored in RB80 and the RI0 flag is set. If these conditions are not met, SBUF0 and RB80 will not be loaded and the RI0 flag will not be set. An interrupt will occur if enabled when either TI0 or RI0 is set. MARK START BIT D0 D1 D2 D3 D4 D5 D6 D7 STOP SPACE BIT BIT TIMES BIT SAMPLING Figure 29.4. 8-Bit UART Timing Diagram 222 Rev. 1.2

C8051F39x/37x 29.2.2. 9-Bit UART 9-bit UART mode uses a total of eleven bits per data byte: a start bit, 8data bits (LSB first), a programma- ble ninth data bit, and a stop bit. The state of the ninth transmit data bit is determined by the value in TB80 (SCON0.3), which is assigned by user software. It can be assigned the value of the parity flag (bit P in reg- ister PSW) for error detection, or used in multiprocessor communications. On receive, the ninth data bit goes into RB80 (SCON0.2) and the stop bit is ignored. Data transmission begins when an instruction writes a data byte to the SBUF0 register. The TI0 Transmit Interrupt Flag (SCON0.1) is set at the end of the transmission (the beginning of the stop-bit time). Data reception can begin any time after the REN0 Receive Enable bit (SCON0.4) is set to 1. After the stop bit is received, the data byte will be loaded into the SBUF0 receive register if the following conditions are met: (1) RI0 must be logic0, and (2) if MCE0 is logic1, the 9th bit must be logic1 (when MCE0 is logic0, the state of the ninth data bit is unimportant). If these conditions are met, the eight bits of data are stored in SBUF0, the ninth bit is stored in RB80, and the RI0 flag is set to 1. If the above conditions are not met, SBUF0 and RB80 will not be loaded and the RI0 flag will not be set to 1. A UART0 interrupt will occur if enabled when either TI0 or RI0 is set to 1. MARK START BIT D0 D1 D2 D3 D4 D5 D6 D7 D8 STOP SPACE BIT BIT TIMES BIT SAMPLING Figure 29.5. 9-Bit UART Timing Diagram Rev. 1.2 223

C8051F39x/37x 29.3. Multiprocessor Communications 9-Bit UART mode supports multiprocessor communication between a master processor and one or more slave processors by special use of the ninth data bit. When a master processor wants to transmit to one or more slaves, it first sends an address byte to select the target(s). An address byte differs from a data byte in that its ninth bit is logic1; in a data byte, the ninth bit is always set to logic0. Setting the MCE0 bit (SCON0.5) of a slave processor configures its UART such that when a stop bit is received, the UART will generate an interrupt only if the ninth bit is logic1 (RB80=1) signifying an address byte has been received. In the UART interrupt handler, software will compare the received address with the slave's own assigned 8-bit address. If the addresses match, the slave will clear its MCE0 bit to enable interrupts on the reception of the following data byte(s). Slaves that weren't addressed leave their MCE0 bits set and do not generate interrupts on the reception of the following data bytes, thereby ignoring the data. Once the entire message is received, the addressed slave resets its MCE0 bit to ignore all transmis- sions until it receives the next address byte. Multiple addresses can be assigned to a single slave and/or a single address can be assigned to multiple slaves, thereby enabling "broadcast" transmissions to more than one slave simultaneously. The master processor can be configured to receive all transmissions or a protocol can be implemented such that the master/slave role is temporarily reversed to enable half-duplex transmission between the original master and slave(s). Master Slave Slave Slave Device Device Device Device V+ RX TX RX TX RX TX RX TX Figure 29.6. UART Multi-Processor Mode Interconnect Diagram 224 Rev. 1.2

C8051F39x/37x SFR Definition 29.1. SCON0: Serial Port 0 Control Bit 7 6 5 4 3 2 1 0 Name S0MODE MCE0 REN0 TB80 RB80 TI0 RI0 Type R/W R R/W R/W R/W R/W R/W R/W Reset 0 1 0 0 0 0 0 0 SFR Address=0x98; SFR Page=All Pages; Bit-Addressable Bit Name Function 7 S0MODE Serial Port 0 Operation Mode. Selects the UART0 Operation Mode. 0: 8-bit UART with Variable Baud Rate. 1: 9-bit UART with Variable Baud Rate. 6 Unused Unused. Read=1b, Write=Don’t Care. 5 MCE0 Multiprocessor Communication Enable. The function of this bit is dependent on the Serial Port 0 Operation Mode: Mode 0: Checks for valid stop bit. 0: Logic level of stop bit is ignored. 1: RI0 will only be activated if stop bit is logic level1. Mode 1: Multiprocessor Communications Enable. 0: Logic level of ninth bit is ignored. 1: RI0 is set and an interrupt is generated only when the ninth bit is logic1. 4 REN0 Receive Enable. 0: UART0 reception disabled. 1: UART0 reception enabled. 3 TB80 Ninth Transmission Bit. The logic level of this bit will be sent as the ninth transmission bit in 9-bit UART Mode (Mode 1). Unused in 8-bit mode (Mode 0). 2 RB80 Ninth Receive Bit. RB80 is assigned the value of the STOP bit in Mode0; it is assigned the value of the 9th data bit in Mode 1. 1 TI0 Transmit Interrupt Flag. Set by hardware when a byte of data has been transmitted by UART0 (after the 8th bit in 8-bit UART Mode, or at the beginning of the STOP bit in 9-bit UART Mode). When the UART0 interrupt is enabled, setting this bit causes the CPU to vector to the UART0 interrupt service routine. This bit must be cleared manually by software. 0 RI0 Receive Interrupt Flag. Set to 1 by hardware when a byte of data has been received by UART0 (set at the STOP bit sampling time). When the UART0 interrupt is enabled, setting this bit to 1 causes the CPU to vector to the UART0 interrupt service routine. This bit must be cleared manually by software. Rev. 1.2 225

C8051F39x/37x SFR Definition 29.2. SBUF0: Serial (UART0) Port Data Buffer Bit 7 6 5 4 3 2 1 0 Name SBUF0[7:0] Type R/W Reset 0 0 0 0 0 0 0 0 SFR Address=0x99; SFR Page=All Pages Bit Name Function 7:0 SBUF0[7:0] Serial Data Buffer Bits 7–0 (MSB–LSB). This SFR accesses two registers; a transmit shift register and a receive latch register. When data is written to SBUF0, it goes to the transmit shift register and is held for serial transmission. Writing a byte to SBUF0 initiates the transmission. A read of SBUF0 returns the contents of the receive latch. 226 Rev. 1.2

C8051F39x/37x Table 29.1. Timer Settings for Standard Baud Rates Using The Internal 49 MHz Oscillator Frequency: 49MHz Target Baud Rate Oscillator Timer Clock SCA1–SCA0 T1M1 Timer 1 Baud Rate % Error Divide Source (pre-scale Reload (bps) Factor select)1 Value (hex) om sc. 211350240000 –00..1352%% 422162 SSYYSSCCLLKK XXXX2 11 00xx29B6 LK fr nal O 5278860000 –00..1352%% 1874084 SSYYSSCCLLKK//142 0010 00 00xxB969 C r S e 9600 –0.32% 5088 SYSCLK/48 00 0 0xCB Y nt S I 2400 0.15% 20448 SYSCLK/48 10 0 0x2B Notes: 1. SCA1–SCA0 and T1M bit definitions can be found in Section 31.1. 2. X=Don’t care. Table 29.2. Timer Settings for Standard Baud Rates Using an External 22.1184 MHz Oscillator Frequency: 22.1184MHz Target Baud Rate Oscillator Timer Clock SCA1–SCA0 T1M1 Timer 1 Baud Rate % Error Divide Source (pre-scale Reload (bps) Factor select)1 Value (hex) 230400 0.00% 96 SYSCLK XX2 1 0xD0 m c. 115200 0.00% 192 SYSCLK XX 1 0xA0 o s 57600 0.00% 384 SYSCLK XX 1 0x40 r O K f al 28800 0.00% 768 SYSCLK / 12 00 0 0xE0 L n 14400 0.00% 1536 SYSCLK / 12 00 0 0xC0 C r S te 9600 0.00% 2304 SYSCLK / 12 00 0 0xA0 Y x S E 2400 0.00% 9216 SYSCLK / 48 10 0 0xA0 1200 0.00% 18432 SYSCLK / 48 10 0 0x40 om sc. 211350240000 00..0000%% 19962 EEXXTTCCLLKK // 88 1111 00 00xxFFA4 LK fr nal O 5278680000 00..0000%% 378648 EEXXTTCCLLKK // 88 1111 00 00xxDE80 C r S e 14400 0.00% 1536 EXTCLK / 8 11 0 0xA0 Y nt S I 9600 0.00% 2304 EXTCLK / 8 11 0 0x70 Notes: 1. SCA1–SCA0 and T1M bit definitions can be found in Section 31.1. 2. X=Don’t care. Rev. 1.2 227

C8051F39x/37x 30. Enhanced Serial Peripheral Interface (SPI0) The Enhanced Serial Peripheral Interface (SPI0) provides access to a flexible, full-duplex synchronous serial bus. SPI0 can operate as a master or slave device in both 3-wire or 4-wire modes, and supports mul- tiple masters and slaves on a single SPI bus. The slave-select (NSS) signal can be configured as an input to select SPI0 in slave mode, or to disable Master Mode operation in a multi-master environment, avoiding contention on the SPI bus when more than one master attempts simultaneous data transfers. NSS can also be configured as a chip-select output in master mode, or disabled for 3-wire operation. Additional gen- eral purpose port I/O pins can be used to select multiple slave devices in master mode. SFR Bus SPI0CKR SPI0CFG SPI0CN SCR7SCR6SCR5SCR4SCR3SCR2SCR1SCR0 SPIBSYMSTENCKPHACKPOLSLVSELNSSINSRMTRXBMT SPIFWCOLMODFRXOVRNNSSMD1NSSMD0TXBMTSPIEN Clock Divide SYSCLK Logic SPI CONTROL LOGIC SPI IRQ Data Path Pin Interface Control Control Tx Data MOSI C SPI0DAT R SCK Transmit Data Buffer O Pin S Control Port I/O S 7 6S5hift4 Re3gist2er1 0 Rx Data Logic MISO B A R Receive Data Buffer NSS Write Read SPI0DAT SPI0DAT SFR Bus Figure 30.1. SPI Block Diagram 228 Rev. 1.2

C8051F39x/37x 30.1. Signal Descriptions The four signals used by SPI0 (MOSI, MISO, SCK, NSS) are described below. 30.1.1. Master Out, Slave In (MOSI) The master-out, slave-in (MOSI) signal is an output from a master device and an input to slave devices. It is used to serially transfer data from the master to the slave. This signal is an output when SPI0 is operat- ing as a master and an input when SPI0 is operating as a slave. Data is transferred most-significant bit first. When configured as a master, MOSI is driven by the MSB of the shift register in both 3- and 4-wire mode. 30.1.2. Master In, Slave Out (MISO) The master-in, slave-out (MISO) signal is an output from a slave device and an input to the master device. It is used to serially transfer data from the slave to the master. This signal is an input when SPI0 is operat- ing as a master and an output when SPI0 is operating as a slave. Data is transferred most-significant bit first. The MISO pin is placed in a high-impedance state when the SPI module is disabled and when the SPI operates in 4-wire mode as a slave that is not selected. When acting as a slave in 3-wire mode, MISO is always driven by the MSB of the shift register. 30.1.3. Serial Clock (SCK) The serial clock (SCK) signal is an output from the master device and an input to slave devices. It is used to synchronize the transfer of data between the master and slave on the MOSI and MISO lines. SPI0 gen- erates this signal when operating as a master. The SCK signal is ignored by a SPI slave when the slave is not selected (NSS=1) in 4-wire slave mode. 30.1.4. Slave Select (NSS) The function of the slave-select (NSS) signal is dependent on the setting of the NSSMD1 and NSSMD0 bits in the SPI0CN register. There are three possible modes that can be selected with these bits: 1. NSSMD[1:0]=00: 3-Wire Master or 3-Wire Slave Mode: SPI0 operates in 3-wire mode, and NSS is disabled. When operating as a slave device, SPI0 is always selected in 3-wire mode. Since no select signal is present, SPI0 must be the only slave on the bus in 3-wire mode. This is intended for point-to- point communication between a master and one slave. 2. NSSMD[1:0]=01: 4-Wire Slave or Multi-Master Mode: SPI0 operates in 4-wire mode, and NSS is enabled as an input. When operating as a slave, NSS selects the SPI0 device. When operating as a master, a 1-to-0 transition of the NSS signal disables the master function of SPI0 so that multiple master devices can be used on the same SPI bus. 3. NSSMD[1:0]=1x: 4-Wire Master Mode: SPI0 operates in 4-wire mode, and NSS is enabled as an output. The setting of NSSMD0 determines what logic level the NSS pin will output. This configuration should only be used when operating SPI0 as a master device. See Figure30.2, Figure30.3, and Figure30.4 for typical connection diagrams of the various operational modes. Note that the setting of NSSMD bits affects the pinout of the device. When in 3-wire master or 3-wire slave mode, the NSS pin will not be mapped by the crossbar. In all other modes, the NSS signal will be mapped to a pin on the device. See Section “27.Port Input/Output” on page173 for general purpose port I/O and crossbar information. Rev. 1.2 229

C8051F39x/37x 30.2. SPI0 Master Mode Operation A SPI master device initiates all data transfers on a SPI bus. SPI0 is placed in master mode by setting the Master Enable flag (MSTEN, SPI0CN.6). Writing a byte of data to the SPI0 data register (SPI0DAT) when in master mode writes to the transmit buffer. If the SPI shift register is empty, the byte in the transmit buffer is moved to the shift register, and a data transfer begins. The SPI0 master immediately shifts out the data serially on the MOSI line while providing the serial clock on SCK. The SPIF (SPI0CN.7) flag is set to logic 1 at the end of the transfer. If interrupts are enabled, an interrupt request is generated when the SPIF flag is set. While the SPI0 master transfers data to a slave on the MOSI line, the addressed SPI slave device simultaneously transfers the contents of its shift register to the SPI master on the MISO line in a full-duplex operation. Therefore, the SPIF flag serves as both a transmit-complete and receive-data-ready flag. The data byte received from the slave is transferred MSB-first into the master's shift register. When a byte is fully shifted into the register, it is moved to the receive buffer where it can be read by the processor by reading SPI0DAT. When configured as a master, SPI0 can operate in one of three different modes: multi-master mode, 3-wire single-master mode, and 4-wire single-master mode. The default, multi-master mode is active when NSS- MD1 (SPI0CN.3)=0 and NSSMD0 (SPI0CN.2)=1. In this mode, NSS is an input to the device, and is used to disable the master SPI0 when another master is accessing the bus. When NSS is pulled low in this mode, MSTEN (SPI0CN.6) and SPIEN (SPI0CN.0) are set to 0 to disable the SPI master device, and a Mode Fault is generated (MODF, SPI0CN.5=1). Mode Fault will generate an interrupt if enabled. SPI0 must be manually re-enabled in software under these circumstances. In multi-master systems, devices will typically default to being slave devices while they are not acting as the system master device. In multi-mas- ter mode, slave devices can be addressed individually (if needed) using general-purpose I/O pins. Figure30.2 shows a connection diagram between two master devices in multiple-master mode. 3-wire single-master mode is active when NSSMD1 (SPI0CN.3)=0 and NSSMD0 (SPI0CN.2)=0. In this mode, NSS is not used, and is not mapped to an external port pin through the crossbar. Any slave devices that must be addressed in this mode should be selected using general-purpose I/O pins. Figure30.3 shows a connection diagram between a master device in 3-wire master mode and a slave device. 4-wire single-master mode is active when NSSMD1 (SPI0CN.3)=1. In this mode, NSS is configured as an output pin, and can be used as a slave-select signal for a single SPI device. In this mode, the output value of NSS is controlled (in software) with the bit NSSMD0 (SPI0CN.2). Additional slave devices can be addressed using general-purpose I/O pins. Figure30.4 shows a connection diagram for a master device in 4-wire master mode and two slave devices. NSS GPIO MISO MISO Master Master MOSI MOSI Device 1 Device 2 SCK SCK GPIO NSS Figure 30.2. Multiple-Master Mode Connection Diagram 230 Rev. 1.2

C8051F39x/37x Master Slave Device Device MISO MISO MOSI MOSI SCK SCK Figure 30.3. 3-Wire Single Master and 3-Wire Single Slave Mode Connection Diagram Master MISO MISO Slave Device MOSI MOSI Device SCK SCK NSS NSS GPIO MISO Slave MOSI Device SCK NSS Figure 30.4. 4-Wire Single Master Mode and 4-Wire Slave Mode Connection Diagram 30.3. SPI0 Slave Mode Operation When SPI0 is enabled and not configured as a master, it will operate as a SPI slave. As a slave, bytes are shifted in through the MOSI pin and out through the MISO pin by a master device controlling the SCK sig- nal. A bit counter in the SPI0 logic counts SCK edges. When 8 bits have been shifted through the shift reg- ister, the SPIF flag is set to logic 1, and the byte is copied into the receive buffer. Data is read from the receive buffer by reading SPI0DAT. A slave device cannot initiate transfers. Data to be transferred to the master device is pre-loaded into the shift register by writing to SPI0DAT. Writes to SPI0DAT are double- buffered, and are placed in the transmit buffer first. If the shift register is empty, the contents of the transmit buffer will immediately be transferred into the shift register. When the shift register already contains data, the SPI will load the shift register with the transmit buffer’s contents after the last SCK edge of the next (or current) SPI transfer. When configured as a slave, SPI0 can be configured for 4-wire or 3-wire operation. The default, 4-wire slave mode, is active when NSSMD1 (SPI0CN.3)=0 and NSSMD0 (SPI0CN.2)=1. In 4-wire mode, the NSS signal is routed to a port pin and configured as a digital input. SPI0 is enabled when NSS is logic 0, and disabled when NSS is logic 1. The bit counter is reset on a falling edge of NSS. Note that the NSS sig- nal must be driven low at least 2 system clocks before the first active edge of SCK for each byte transfer. Figure30.4 shows a connection diagram between two slave devices in 4-wire slave mode and a master device. The 3-wire slave mode is active when NSSMD1 (SPI0CN.3)=0 and NSSMD0 (SPI0CN.2)=0. NSS is not used in this mode, and is not mapped to an external port pin through the crossbar. Since there is no way of Rev. 1.2 231

C8051F39x/37x uniquely addressing the device in 3-wire slave mode, SPI0 must be the only slave device present on the bus. It is important to note that in 3-wire slave mode there is no external means of resetting the bit counter that determines when a full byte has been received. The bit counter can only be reset by disabling and re- enabling SPI0 with the SPIEN bit. Figure30.3 shows a connection diagram between a slave device in 3- wire slave mode and a master device. 30.4. SPI0 Interrupt Sources When SPI0 interrupts are enabled, the following four flags will generate an interrupt when they are set to logic 1: All of the following bits must be cleared by software.  The SPI Interrupt Flag, SPIF (SPI0CN.7) is set to logic 1 at the end of each byte transfer. This flag can occur in all SPI0 modes.  The Write Collision Flag, WCOL (SPI0CN.6) is set to logic 1 if a write to SPI0DAT is attempted when the transmit buffer has not been emptied to the SPI shift register. When this occurs, the write to SPI0DAT will be ignored, and the transmit buffer will not be written.This flag can occur in all SPI0 modes.  The Mode Fault Flag MODF (SPI0CN.5) is set to logic 1 when SPI0 is configured as a master, and for multi-master mode and the NSS pin is pulled low. When a Mode Fault occurs, the MSTEN and SPIEN bits in SPI0CN are set to logic 0 to disable SPI0 and allow another master device to access the bus.  The Receive Overrun Flag RXOVRN (SPI0CN.4) is set to logic 1 when configured as a slave, and a transfer is completed and the receive buffer still holds an unread byte from a previous transfer. The new byte is not transferred to the receive buffer, allowing the previously received data byte to be read. The data byte which caused the overrun is lost. 30.5. Serial Clock Phase and Polarity Four combinations of serial clock phase and polarity can be selected using the clock control bits in the SPI0 Configuration Register (SPI0CFG). The CKPHA bit (SPI0CFG.5) selects one of two clock phases (edge used to latch the data). The CKPOL bit (SPI0CFG.4) selects between an active-high or active-low clock. Both master and slave devices must be configured to use the same clock phase and polarity. SPI0 should be disabled (by clearing the SPIEN bit, SPI0CN.0) when changing the clock phase or polarity. The clock and data line relationships for master mode are shown in Figure30.5. For slave mode, the clock and data relationships are shown in Figure30.6 and Figure30.7. Note that CKPHA should be set to 0 on both the master and slave SPI when communicating between two Silicon Labs C8051 devices. The SPI0 Clock Rate Register (SPI0CKR) as shown in SFR Definition 30.3 controls the master mode serial clock frequency. This register is ignored when operating in slave mode. When the SPI is configured as a master, the maximum data transfer rate (bits/sec) is one-half the system clock frequency or 12.5 MHz, whichever is slower. When the SPI is configured as a slave, the maximum data transfer rate (bits/sec) for full-duplex operation is 1/10 the system clock frequency, provided that the master issues SCK, NSS (in 4- wire slave mode), and the serial input data synchronously with the slave’s system clock. If the master issues SCK, NSS, and the serial input data asynchronously, the maximum data transfer rate (bits/sec) must be less than 1/10 the system clock frequency. In the special case where the master only wants to transmit data to the slave and does not need to receive data from the slave (i.e. half-duplex operation), the SPI slave can receive data at a maximum data transfer rate (bits/sec) of 1/4 the system clock frequency. This is provided that the master issues SCK, NSS, and the serial input data synchronously with the slave’s system clock. 232 Rev. 1.2

C8051F39x/37x SCK (CKPOL=0, CKPHA=0) SCK (CKPOL=0, CKPHA=1) SCK (CKPOL=1, CKPHA=0) SCK (CKPOL=1, CKPHA=1) MISO/MOSI MSB Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 0 NSS (Must Remain High in Multi-Master Mode) Figure 30.5. Master Mode Data/Clock Timing SCK (CKPOL=0, CKPHA=0) SCK (CKPOL=1, CKPHA=0) MOSI MSB Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 0 MISO MSB Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 0 NSS (4-Wire Mode) Figure 30.6. Slave Mode Data/Clock Timing (CKPHA = 0) Rev. 1.2 233

C8051F39x/37x SCK (CKPOL=0, CKPHA=1) SCK (CKPOL=1, CKPHA=1) MOSI MSB Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 0 MISO MSB Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 0 NSS (4-Wire Mode) Figure 30.7. Slave Mode Data/Clock Timing (CKPHA = 1) 30.6. SPI Special Function Registers SPI0 is accessed and controlled through four special function registers in the system controller: SPI0CN Control Register, SPI0DAT Data Register, SPI0CFG Configuration Register, and SPI0CKR Clock Rate Register. The four special function registers related to the operation of the SPI0 Bus are described in the following figures. 234 Rev. 1.2

C8051F39x/37x SFR Definition 30.1. SPI0CFG: SPI0 Configuration Bit 7 6 5 4 3 2 1 0 Name SPIBSY MSTEN CKPHA CKPOL SLVSEL NSSIN SRMT RXBMT Type R R/W R/W R/W R R R R Reset 0 0 0 0 0 1 1 1 SFR Address=0xA1; SFR Page=All Pages Bit Name Function 7 SPIBSY SPI Busy. This bit is set to logic 1 when a SPI transfer is in progress (master or slave mode). 6 MSTEN Master Mode Enable. 0: Disable master mode. Operate in slave mode. 1: Enable master mode. Operate as a master. 5 CKPHA SPI0 Clock Phase. 0: Data centered on first edge of SCK period.* 1: Data centered on second edge of SCK period.* 4 CKPOL SPI0 Clock Polarity. 0: SCK line low in idle state. 1: SCK line high in idle state. 3 SLVSEL Slave Selected Flag. This bit is set to logic 1 whenever the NSS pin is low indicating SPI0 is the selected slave. It is cleared to logic 0 when NSS is high (slave not selected). This bit does not indicate the instantaneous value at the NSS pin, but rather a de-glitched version of the pin input. 2 NSSIN NSS Instantaneous Pin Input. This bit mimics the instantaneous value that is present on the NSS port pin at the time that the register is read. This input is not de-glitched. 1 SRMT Shift Register Empty (valid in slave mode only). This bit will be set to logic 1 when all data has been transferred in/out of the shift reg- ister, and there is no new information available to read from the transmit buffer or write to the receive buffer. It returns to logic 0 when a data byte is transferred to the shift register from the transmit buffer or by a transition on SCK. SRMT=1 when in Master Mode. 0 RXBMT Receive Buffer Empty (valid in slave mode only). This bit will be set to logic 1 when the receive buffer has been read and contains no new information. If there is new information available in the receive buffer that has not been read, this bit will return to logic 0. RXBMT=1 when in Master Mode. Note: In slave mode, data on MOSI is sampled in the center of each data bit. In master mode, data on MISO is sampled one SYSCLK before the end of each data bit, to provide maximum settling time for the slave device. See Table30.1 for timing parameters. Rev. 1.2 235

C8051F39x/37x SFR Definition 30.2. SPI0CN: SPI0 Control Bit 7 6 5 4 3 2 1 0 Name SPIF WCOL MODF RXOVRN NSSMD[1:0] TXBMT SPIEN Type R/W R/W R/W R/W R/W R R/W Reset 0 0 0 0 0 1 1 0 SFR Address=0xF8; SFR Page=All Pages; Bit-Addressable Bit Name Function 7 SPIF SPI0 Interrupt Flag. This bit is set to logic 1 by hardware at the end of a data transfer. If SPI interrupts are enabled, an interrupt will be generated. This bit is not automatically cleared by hardware, and must be cleared by software. 6 WCOL Write Collision Flag. This bit is set to logic 1 if a write to SPI0DAT is attempted when TXBMT is 0. When this occurs, the write to SPI0DAT will be ignored, and the transmit buffer will not be written. If SPI interrupts are enabled, an interrupt will be generated. This bit is not automatically cleared by hardware, and must be cleared by software. 5 MODF Mode Fault Flag. This bit is set to logic 1 by hardware when a master mode collision is detected (NSS is low, MSTEN=1, and NSSMD[1:0]=01). If SPI interrupts are enabled, an inter- rupt will be generated. This bit is not automatically cleared by hardware, and must be cleared by software. 4 RXOVRN Receive Overrun Flag (valid in slave mode only). This bit is set to logic 1 by hardware when the receive buffer still holds unread data from a previous transfer and the last bit of the current transfer is shifted into the SPI0 shift register. If SPI interrupts are enabled, an interrupt will be generated. This bit is not automatically cleared by hardware, and must be cleared by software. 3:2 NSSMD[1:0] Slave Select Mode. Selects between the following NSS operation modes: (See Section 30.2 and Section 30.3). 00: 3-Wire Slave or 3-Wire Master Mode. NSS signal is not routed to a port pin. 01: 4-Wire Slave or Multi-Master Mode (Default). NSS is an input to the device. 1x: 4-Wire Single-Master Mode. NSS signal is mapped as an output from the device and will assume the value of NSSMD0. 1 TXBMT Transmit Buffer Empty. This bit will be set to logic 0 when new data has been written to the transmit buffer. When data in the transmit buffer is transferred to the SPI shift register, this bit will be set to logic 1, indicating that it is safe to write a new byte to the transmit buffer. 0 SPIEN SPI0 Enable. 0: SPI disabled. 1: SPI enabled. 236 Rev. 1.2

C8051F39x/37x SFR Definition 30.3. SPI0CKR: SPI0 Clock Rate Bit 7 6 5 4 3 2 1 0 Name SCR[7:0] Type R/W Reset 0 0 0 0 0 0 0 0 SFR Address=0xA2; SFR Page=All Pages Bit Name Function 7:0 SCR[7:0] SPI0 Clock Rate. These bits determine the frequency of the SCK output when the SPI0 module is configured for master mode operation. The SCK clock frequency is a divided version of the system clock, and is given in the following equation, where SYSCLK is the system clock frequency and SPI0CKR is the 8-bit value held in the SPI0CKR register. SYSCLK f = ----------------------------------------------------------- SCK 2 SPI0CKR[7:0] + 1 for 0 <= SPI0CKR <= 255 Example: If SYSCLK=2MHz and SPI0CKR=0x04, 2000000 f = -------------------------- SCK 24+ 1 f = 200kHz SCK Rev. 1.2 237

C8051F39x/37x SFR Definition 30.4. SPI0DAT: SPI0 Data Bit 7 6 5 4 3 2 1 0 Name SPI0DAT[7:0] Type R/W Reset 0 0 0 0 0 0 0 0 SFR Address=0xA3; SFR Page=All Pages Bit Name Function 7:0 SPI0DAT[7:0] SPI0 Transmit and Receive Data. The SPI0DAT register is used to transmit and receive SPI0 data. Writing data to SPI0DAT places the data into the trans- mit buffer and initiates a transfer when in Master Mode. A read of SPI0DAT returns the contents of the receive buffer. SCK* T T MCKH MCKL T T MIS MIH MISO MOSI * SCK is shown for CKPOL = 0. SCK is the opposite polarity for CKPOL = 1. Figure 30.8. SPI Master Timing (CKPHA = 0) 238 Rev. 1.2

C8051F39x/37x SCK* T T MCKH MCKL T T MIS MIH MISO MOSI * SCK is shown for CKPOL = 0. SCK is the opposite polarity for CKPOL = 1. Figure 30.9. SPI Master Timing (CKPHA = 1) NSS T T T SE CKL SD SCK* T CKH T T SIS SIH MOSI T T T SEZ SOH SDZ MISO * SCK is shown for CKPOL = 0. SCK is the opposite polarity for CKPOL = 1. Figure 30.10. SPI Slave Timing (CKPHA = 0) Rev. 1.2 239

C8051F39x/37x NSS T T T SE CKL SD SCK* T CKH T T SIS SIH MOSI T T T T SEZ SOH SLH SDZ MISO * SCK is shown for CKPOL = 0. SCK is the opposite polarity for CKPOL = 1. Figure 30.11. SPI Slave Timing (CKPHA = 1) 240 Rev. 1.2

C8051F39x/37x Table 30.1. SPI Slave Timing Parameters Parameter Description Min Max Units Master Mode Timing (See Figure30.8 and Figure30.9) T SCK High Time 1xT — ns MCKH SYSCLK T SCK Low Time 1xT — ns MCKL SYSCLK T MISO Valid to SCK Shift Edge 1xT + 20 — ns MIS SYSCLK T SCK Shift Edge to MISO Change 0 — ns MIH Slave Mode Timing (See Figure30.10 and Figure30.11) T NSS Falling to First SCK Edge 2xT — ns SE SYSCLK T Last SCK Edge to NSS Rising 2xT — ns SD SYSCLK T NSS Falling to MISO Valid — 4xT ns SEZ SYSCLK T NSS Rising to MISO High-Z — 4xT ns SDZ SYSCLK T SCK High Time 5xT — ns CKH SYSCLK T SCK Low Time 5xT — ns CKL SYSCLK T MOSI Valid to SCK Sample Edge 2xT — ns SIS SYSCLK T SCK Sample Edge to MOSI Change 2xT — ns SIH SYSCLK T SCK Shift Edge to MISO Change — 4xT ns SOH SYSCLK T Last SCK Edge to MISO Change 6xT 8xT ns SLH SYSCLK SYSCLK (CKPHA=1 ONLY) Note: T is equal to one period of the device system clock (SYSCLK). SYSCLK Rev. 1.2 241

C8051F39x/37x 31. Timers Each MCU includes six counter/timers: two are 16-bit counter/timers compatible with those found in the standard 8051, and four are 16-bit auto-reload timer for use with the SMBus or for general purpose use. These timers can be used to measure time intervals, count external events and generate periodic interrupt requests. Timer0 and Timer1 are nearly identical and have four primary modes of operation. Timer2, 3, 4, and 5 offer 16-bit and split 8-bit timer functionality with auto-reload. Timer 0 and Timer 1 Modes: Timer 2, 3, 4, and 5 Modes: 13-bit counter/timer 16-bit timer with auto-reload 16-bit counter/timer 8-bit counter/timer with auto-reload Two 8-bit timers with auto-reload Two 8-bit counter/timers (Timer 0 only) Timers0 and 1 may be clocked by one of five sources, determined by the Timer Mode Select bits (T1M– T0M) and the Clock Scale bits (SCA1–SCA0). The Clock Scale bits define a pre-scaled clock from which Timer0 and/or Timer1 may be clocked (See SFR Definition 31.1 for pre-scaled clock selection). Timer0/1 may then be configured to use this pre-scaled clock signal or the system clock. Timer2, 3, 4, and 5 may be clocked by the system clock, the system clock divided by 12, or the external oscillator clock source divided by 8. Timer0 and Timer1 may also be operated as counters. When functioning as a counter, a counter/timer register is incremented on each high-to-low transition at the selected input pin (T0 or T1). Events with a fre- quency of up to one-fourth the system clock frequency can be counted. The input signal need not be peri- odic, but it should be held at a given level for at least two full system clock cycles to ensure the level is properly sampled. 242 Rev. 1.2

C8051F39x/37x SFR Definition 31.1. CKCON: Clock Control Bit 7 6 5 4 3 2 1 0 Name T3MH T3ML T2MH T2ML T1M T0M SCA[1:0] Type R/W R/W R/W R/W R/W R/W R/W Reset 0 0 0 0 0 0 0 0 SFR Address=0x8E; SFR Page=All Pages Bit Name Function 7 T3MH Timer3 High Byte Clock Select. Selects the clock supplied to the Timer3 high byte (split 8-bit timer mode only). 0: Timer3 high byte uses the clock defined by the T3XCLK bit in TMR3CN. 1: Timer3 high byte uses the system clock. 6 T3ML Timer3 Low Byte Clock Select. Selects the clock supplied to Timer3. Selects the clock supplied to the lower 8- bit timer in split 8-bit timer mode. 0: Timer3 low byte uses the clock defined by the T3XCLK bit in TMR3CN. 1: Timer3 low byte uses the system clock. 5 T2MH Timer2 High Byte Clock Select. Selects the clock supplied to the Timer2 high byte (split 8-bit timer mode only). 0: Timer2 high byte uses the clock defined by the T2XCLK bit in TMR2CN. 1: Timer2 high byte uses the system clock. 4 T2ML Timer2 Low Byte Clock Select. Selects the clock supplied to Timer2. If Timer2 is configured in split 8-bit timer mode, this bit selects the clock supplied to the lower 8-bit timer. 0: Timer2 low byte uses the clock defined by the T2XCLK bit in TMR2CN. 1: Timer2 low byte uses the system clock. 3 T1 Timer1 Clock Select. Selects the clock source supplied to Timer1. Ignored when C/T1is set to 1. 0: Timer1 uses the clock defined by the prescale bits SCA[1:0]. 1: Timer1 uses the system clock. 2 T0 Timer0 Clock Select. Selects the clock source supplied to Timer0. Ignored when C/T0 is set to 1. 0: Counter/Timer0 uses the clock defined by the prescale bits SCA[1:0]. 1: Counter/Timer0 uses the system clock. 1:0 SCA[1:0] Timer0/1 Prescale Bits. These bits control the Timer0/1 Clock Prescaler: 00: System clock divided by 12 01: System clock divided by 4 10: System clock divided by 48 11: External clock divided by 8 (synchronized with the system clock) Rev. 1.2 243

C8051F39x/37x SFR Definition 31.2. CKCON1: Clock Control 1 Bit 7 6 5 4 3 2 1 0 Name T5MH T5ML T4MH T4ML Type R R R R R/W R/W R/W R/W Reset 0 0 0 0 0 0 0 0 SFR Address=0xF4; SFR Page=All Pages Bit Name Function 7:4 Unused Read=0000b; Write=don’t care 3 T5MH Timer5 High Byte Clock Select. Selects the clock supplied to the Timer5 high byte (split 8-bit timer mode only). 0: Timer5 high byte uses the clock defined by the T5XCLK bit in TMR5CN. 1: Timer5 high byte uses the system clock. 2 T5ML Timer5 Low Byte Clock Select. Selects the clock supplied to Timer5. Selects the clock supplied to the lower 8-bit timer in split 8-bit timer mode. 0: Timer5 low byte uses the clock defined by the T5XCLK bit in TMR5CN. 1: Timer5 low byte uses the system clock. 1 T4MH Timer4 High Byte Clock Select. Selects the clock supplied to the Timer4 high byte (split 8-bit timer mode only). 0: Timer4 high byte uses the clock defined by the T4XCLK bit in TMR4CN. 1: Timer4 high byte uses the system clock. 0 T4ML Timer4 Low Byte Clock Select. Selects the clock supplied to Timer4. If Timer4 is configured in split 8-bit timer mode, this bit selects the clock supplied to the lower 8-bit timer. 0: Timer4 low byte uses the clock defined by the T4XCLK bit in TMR4CN. 1: Timer4 low byte uses the system clock. 244 Rev. 1.2

C8051F39x/37x 31.1. Timer 0 and Timer 1 Each timer is implemented as a 16-bit register accessed as two separate bytes: a low byte (TL0 or TL1) and a high byte (TH0 or TH1). The Counter/Timer Control register (TCON) is used to enable Timer0 and Timer1 as well as indicate status. Timer0 interrupts can be enabled by setting the ET0 bit in the IE regis- ter (Section “20.2.Interrupt Register Descriptions” on page120); Timer1 interrupts can be enabled by set- ting the ET1 bit in the IE register (Section “20.2.Interrupt Register Descriptions” on page120). Both counter/timers operate in one of four primary modes selected by setting the Mode Select bits T1M1–T0M0 in the Counter/Timer Mode register (TMOD). Each timer can be configured independently. Each operating mode is described below. 31.1.1. Mode 0: 13-bit Counter/Timer Timer0 and Timer1 operate as 13-bit counter/timers in Mode0. The following describes the configuration and operation of Timer0. However, both timers operate identically, and Timer1 is configured in the same manner as described for Timer0. The TH0 register holds the eight MSBs of the 13-bit counter/timer. TL0 holds the five LSBs in bit positions TL0.4–TL0.0. The three upper bits of TL0 (TL0.7–TL0.5) are indeterminate and should be masked out or ignored when reading. As the 13-bit timer register increments and overflows from 0x1FFF (all ones) to 0x0000, the timer overflow flag TF0 in TCON is set and an interrupt will occur if Timer0 interrupts are enabled. The C/T0 bit in the TMOD register selects the counter/timer's clock source. When C/T0 is set to logic1, high-to-low transitions at the selected Timer0 input pin (T0) increment the timer register (Refer to Section “27.3.Priority Crossbar Decoder” on page178 for information on selecting and configuring external I/O pins). Clearing C/T selects the clock defined by the T0M bit in register CKCON. When T0M is set, Timer0 is clocked by the system clock. When T0M is cleared, Timer0 is clocked by the source selected by the Clock Scale bits in CKCON (see SFR Definition 31.1). Setting the TR0 bit (TCON.4) enables the timer when either GATE0 in the TMOD register is logic0 or the input signal INT0 is active as defined by bit IN0PL in register IT01CF (see SFR Definition 20.10). Setting GATE0 to 1 allows the timer to be controlled by the external input signal INT0 (see Section “20.2.Interrupt Register Descriptions” on page120), facilitating pulse width measurements TR0 GATE0 INT0 Counter/Timer 0 X X Disabled 1 0 X Enabled 1 1 0 Disabled 1 1 1 Enabled Note: X=Don't Care Setting TR0 does not force the timer to reset. The timer registers should be loaded with the desired initial value before the timer is enabled. TL1 and TH1 form the 13-bit register for Timer1 in the same manner as described above for TL0 and TH0. Timer1 is configured and controlled using the relevant TCON and TMOD bits just as with Timer0. The input signal INT0 is used with Timer1; the /INT1 polarity is defined by bit IN1PL in register IT01CF (see SFR Definition 20.10). Rev. 1.2 245

C8051F39x/37x TMOD IT01CF GCTTGCTT I I I I I I I I T0M A / 1 1A / 0 0 NNNNNNNN TTMMTTMM 1 1 1 1 0 0 0 0 E1 1 0E0 1 0 PSSSPSSS 1 0 L L L L L L L L 2 1 0 2 1 0 Pre-scaled Clock 0 0 SYSCLK 1 1 TF1 T0 TR1 TCLK TL0 TH0 TF0 Interrupt TR0 TR0 (5 bits) (8 bits) N IE1 GATE0 O IT1 Crossbar TC IIET00 IN0PL /INT0 XOR Figure 31.1. T0 Mode 0 Block Diagram 31.1.2. Mode 1: 16-bit Counter/Timer Mode1 operation is the same as Mode0, except that the counter/timer registers use all 16bits. The counter/timers are enabled and configured in Mode1 in the same manner as for Mode0. 246 Rev. 1.2

C8051F39x/37x 31.1.3. Mode 2: 8-bit Counter/Timer with Auto-Reload Mode2 configures Timer0 and Timer1 to operate as 8-bit counter/timers with automatic reload of the start value. TL0 holds the count and TH0 holds the reload value. When the counter in TL0 overflows from all ones to 0x00, the timer overflow flag TF0 in the TCON register is set and the counter in TL0 is reloaded from TH0. If Timer0 interrupts are enabled, an interrupt will occur when the TF0 flag is set. The reload value in TH0 is not changed. TL0 must be initialized to the desired value before enabling the timer for the first count to be correct. When in Mode2, Timer1 operates identically to Timer0. Both counter/timers are enabled and configured in Mode2 in the same manner as Mode0. Setting the TR0 bit (TCON.4) enables the timer when either GATE0 in the TMOD register is logic0 or when the input signal INT0 is active as defined by bit IN0PL in register IT01CF (see Section “20.3.External Interrupts INT0 and INT1” on page128 for details on the external input signals INT0 and INT1). TMOD IT01CF GCT TGCT T I I I I I I I I A / 1 1 A / 0 0 NNNNNNNN T0M T TMMT TMM 1 1 1 1 0 0 0 0 E 1 1 0 E 0 1 0 PSSSPSSS 1 0 L L L L L L L L 2 1 0 2 1 0 Pre-scaled Clock 0 0 SYSCLK 1 1 T0 TF1 TCLK TL0 TR1 TF0 Interrupt (8 bits) TR0 TR0 ON IIET11 Crossbar GATE0 TC IIET00 TH0 Reload (8 bits) IN0PL /INT0 XOR Figure 31.2. T0 Mode 2 Block Diagram Rev. 1.2 247

C8051F39x/37x 31.1.4. Mode 3: Two 8-bit Counter/Timers (Timer 0 Only) In Mode3, Timer0 is configured as two separate 8-bit counter/timers held in TL0 and TH0. The counter/ timer in TL0 is controlled using the Timer0 control/status bits in TCON and TMOD: TR0, C/T0, GATE0 and TF0. TL0 can use either the system clock or an external input signal as its timebase. The TH0 register is restricted to a timer function sourced by the system clock or prescaled clock. TH0 is enabled using the Timer1 run control bit TR1. TH0 sets the Timer1 overflow flag TF1 on overflow and thus controls the Timer1 interrupt. Timer1 is inactive in Mode3. When Timer0 is operating in Mode3, Timer1 can be operated in Modes0, 1 or 2, but cannot be clocked by external signals nor set the TF1 flag and generate an interrupt. However, the Timer1 overflow can be used to generate baud rates for the SMBus and/or UART, and/or initiate ADC conversions. While Timer0 is operating in Mode3, Timer1 run control is handled through its mode set- tings. To run Timer1 while Timer0 is in Mode3, set the Timer1 Mode as 0, 1, or 2. To disable Timer1, configure it for Mode3. TMOD GCTTGCTT T0M A / 1 1A / 0 0 TTMMTTMM E1 1 0E0 1 0 1 0 Pre-scaled Clock 0 TR1 TH0 TF1 Interrupt (8 bits) TR1 TF0 Interrupt SYSCLK 1 TR0 0 N IE1 O IT1 C IE0 T IT0 1 T0 TL0 (8 bits) TR0 Crossbar GATE0 IN0PL /INT0 XOR Figure 31.3. T0 Mode 3 Block Diagram 248 Rev. 1.2

C8051F39x/37x SFR Definition 31.3. TCON: Timer Control Bit 7 6 5 4 3 2 1 0 Name TF1 TR1 TF0 TR0 IE1 IT1 IE0 IT0 Type R/W R/W R/W R/W R/W R/W R/W R/W Reset 0 0 0 0 0 0 0 0 SFR Address=0x88; SFR Page=All Pages; Bit-Addressable Bit Name Function 7 TF1 Timer1 Overflow Flag. Set to 1 by hardware when Timer1 overflows. This flag can be cleared by software but is automatically cleared when the CPU vectors to the Timer1 interrupt service routine. 6 TR1 Timer1 Run Control. Timer1 is enabled by setting this bit to 1. 5 TF0 Timer0 Overflow Flag. Set to 1 by hardware when Timer0 overflows. This flag can be cleared by software but is automatically cleared when the CPU vectors to the Timer0 interrupt service routine. 4 TR0 Timer0 Run Control. Timer0 is enabled by setting this bit to 1. 3 IE1 External Interrupt1. This flag is set by hardware when an edge/level of type defined by IT1 is detected. It can be cleared by software but is automatically cleared when the CPU vectors to the External Interrupt1 service routine in edge-triggered mode. 2 IT1 Interrupt1 Type Select. This bit selects whether the configured /INT1 interrupt will be edge or level sensi- tive. /INT1 is configured active low or high by the IN1PL bit in the IT01CF register (see SFR Definition 20.10). 0: /INT1 is level triggered. 1: /INT1 is edge triggered. 1 IE0 External Interrupt0. This flag is set by hardware when an edge/level of type defined by IT1 is detected. It can be cleared by software but is automatically cleared when the CPU vectors to the External Interrupt0 service routine in edge-triggered mode. 0 IT0 Interrupt0 Type Select. This bit selects whether the configured INT0 interrupt will be edge or level sensi- tive. INT0 is configured active low or high by the IN0PL bit in register IT01CF (see SFR Definition 20.10). 0: INT0 is level triggered. 1: INT0 is edge triggered. Rev. 1.2 249

C8051F39x/37x SFR Definition 31.4. TMOD: Timer Mode Bit 7 6 5 4 3 2 1 0 Name GATE1 C/T1 T1M[1:0] GATE0 C/T0 T0M[1:0] Type R/W R/W R/W R/W R/W R/W Reset 0 0 0 0 0 0 0 0 SFR Address=0x89; SFR Page=All Pages Bit Name Function 7 GATE1 Timer1 Gate Control. 0: Timer1 enabled when TR1=1 irrespective of INT1 logic level. 1: Timer1 enabled only when TR1=1 AND INT1 is active as defined by bit IN1PL in register IT01CF (see SFR Definition 20.10). 6 C/T1 Counter/Timer1 Select. 0: Timer: Timer1 incremented by clock defined by T1M bit in register CKCON. 1: Counter: Timer1 incremented by high-to-low transitions on external pin (T1). 5:4 T1M[1:0] Timer1 Mode Select. These bits select the Timer1 operation mode. 00: Mode 0, 13-bit Counter/Timer 01: Mode 1, 16-bit Counter/Timer 10: Mode 2, 8-bit Counter/Timer with Auto-Reload 11: Mode 3, Timer 1 Inactive 3 GATE0 Timer0 Gate Control. 0: Timer0 enabled when TR0=1 irrespective of INT0 logic level. 1: Timer0 enabled only when TR0=1 AND INT0 is active as defined by bit IN0PL in register IT01CF (see SFR Definition 20.10). 2 C/T0 Counter/Timer0 Select. 0: Timer: Timer0 incremented by clock defined by T0M bit in register CKCON. 1: Counter: Timer0 incremented by high-to-low transitions on external pin (T0). 1:0 T0M[1:0] Timer0 Mode Select. These bits select the Timer0 operation mode. 00: Mode 0, 13-bit Counter/Timer 01: Mode 1, 16-bit Counter/Timer 10: Mode 2, 8-bit Counter/Timer with Auto-Reload 11: Mode 3, Two 8-bit Counter/Timers 250 Rev. 1.2

C8051F39x/37x SFR Definition 31.5. TL0: Timer 0 Low Byte Bit 7 6 5 4 3 2 1 0 Name TL0[7:0] Type R/W Reset 0 0 0 0 0 0 0 0 SFR Address=0x8A; SFR Page=All Pages Bit Name Function 7:0 TL0[7:0] Timer0 Low Byte. The TL0 register is the low byte of the 16-bit Timer0. SFR Definition 31.6. TL1: Timer 1 Low Byte Bit 7 6 5 4 3 2 1 0 Name TL1[7:0] Type R/W Reset 0 0 0 0 0 0 0 0 SFR Address=0x8B; SFR Page=All Pages Bit Name Function 7:0 TL1[7:0] Timer1 Low Byte. The TL1 register is the low byte of the 16-bit Timer1. Rev. 1.2 251

C8051F39x/37x SFR Definition 31.7. TH0: Timer 0 High Byte Bit 7 6 5 4 3 2 1 0 Name TH0[7:0] Type R/W Reset 0 0 0 0 0 0 0 0 SFR Address=0x8C; SFR Page=All Pages Bit Name Function 7:0 TH0[7:0] Timer0 High Byte. The TH0 register is the high byte of the 16-bit Timer0. SFR Definition 31.8. TH1: Timer 1 High Byte Bit 7 6 5 4 3 2 1 0 Name TH1[7:0] Type R/W Reset 0 0 0 0 0 0 0 0 SFR Address=0x8D; SFR Page=All Pages Bit Name Function 7:0 TH1[7:0] Timer1 High Byte. The TH1 register is the high byte of the 16-bit Timer1. 252 Rev. 1.2

C8051F39x/37x 31.2. Timer 2 Timer2 is a 16-bit timer formed by two 8-bit SFRs: TMR2L (low byte) and TMR2H (high byte). Timer2 may operate in 16-bit auto-reload mode or (split) 8-bit auto-reload mode. The T2SPLIT bit (TMR2CN.3) defines the Timer2 operation mode. Timer2 may be clocked by the system clock, the system clock divided by 12, or the external oscillator source divided by 8. The external clock mode is ideal for real-time clock (RTC) functionality, where the internal oscillator drives the system clock while Timer 2 (and/or the PCA) is clocked by an external preci- sion oscillator. Note that the external oscillator source divided by 8 is synchronized with the system clock. 31.2.1. 16-bit Timer with Auto-Reload When T2SPLIT (TMR2CN.3) is zero, Timer2 operates as a 16-bit timer with auto-reload. Timer2 can be clocked by SYSCLK, SYSCLK divided by 12, or the external oscillator clock source divided by 8. As the 16-bit timer register increments and overflows from 0xFFFF to 0x0000, the 16-bit value in the Timer2 reload registers (TMR2RLH and TMR2RLL) is loaded into the Timer2 register as shown in Figure31.4, and the Timer2 High Byte Overflow Flag (TMR2CN.7) is set. If Timer2 interrupts are enabled (if IE.5 is set), an interrupt will be generated on each Timer2 overflow. Additionally, if Timer2 interrupts are enabled and the TF2LEN bit is set (TMR2CN.5), an interrupt will be generated each time the lower 8 bits (TMR2L) overflow from 0xFF to 0x00. CKCON TTTTTTSS 332210CC T2XCLK MMMMMMAA HLHL 10 To ADC, SYSCLK / 12 0 TL2 To SMBus SMBus Overflow 0 External Clock / 8 1 TR2 TCLK TMR2L TMR2H TTFF22HL Interrupt CN TF2LEN SYSCLK 1 2 TF2CEN R T2SPLIT M TR2 T T2XCLK TMR2RLL TMR2RLH Reload Figure 31.4. Timer 2 16-Bit Mode Block Diagram Rev. 1.2 253

C8051F39x/37x 31.2.2. 8-bit Timers with Auto-Reload When T2SPLIT is set, Timer2 operates as two 8-bit timers (TMR2H and TMR2L). Both 8-bit timers oper- ate in auto-reload mode as shown in Figure31.5. TMR2RLL holds the reload value for TMR2L; TMR2RLH holds the reload value for TMR2H. The TR2 bit in TMR2CN handles the run control for TMR2H. TMR2L is always running when configured for 8-bit Mode. Each 8-bit timer may be configured to use SYSCLK, SYSCLK divided by 12, or the external oscillator clock source divided by 8. The Timer2 Clock Select bits (T2MH and T2ML in CKCON) select either SYSCLK or the clock defined by the Timer2 External Clock Select bit (T2XCLK in TMR2CN), as follows: T2MH T2XCLK TMR2H Clock Source T2ML T2XCLK TMR2L Clock Source 0 0 SYSCLK / 12 0 0 SYSCLK / 12 0 1 External Clock / 8 0 1 External Clock / 8 1 X SYSCLK 1 X SYSCLK The TF2H bit is set when TMR2H overflows from 0xFF to 0x00; the TF2L bit is set when TMR2L overflows from 0xFF to 0x00. When Timer2 interrupts are enabled (IE.5), an interrupt is generated each time TMR2H overflows. If Timer2 interrupts are enabled and TF2LEN (TMR2CN.5) is set, an interrupt is gener- ated each time either TMR2L or TMR2H overflows. When TF2LEN is enabled, software must check the TF2H and TF2L flags to determine the source of the Timer2 interrupt. The TF2H and TF2L interrupt flags are not cleared by hardware and must be manually cleared by software. CKCON T2XCLK TTTTTTSS 3 32 210CC MMMMMMAA Reload HLHL 10 TMR2RLH To SMBus SYSCLK / 12 0 0 External Clock / 8 1 TCLK TR2 TMR2H TF2H Interrupt TF2L 1 TF2LEN N TF2CEN C T2SPLIT Reload R2 TR2 TMR2RLL M SYSCLK T T2XCLK 1 TCLK TMR2L To ADC, SMBus 0 Figure 31.5. Timer 2 8-Bit Mode Block Diagram 254 Rev. 1.2

C8051F39x/37x 31.2.3. Low-Frequency Oscillator (LFO) Capture Mode The Low-Frequency Oscillator Capture Mode allows the LFO clock to be measured against the system clock or an external oscillator source. Timer2 can be clocked from the system clock, the system clock divided by 12, or the external oscillator divided by 8, depending on the T2ML (CKCON.4), and T2XCLK settings. Setting TF2CEN to 1 enables the LFO Capture Mode for Timer2. In this mode, T2SPLIT should be set to 0, as the full 16-bit timer is used. Upon a falling edge of the low-frequency oscillator, the contents of Timer 2 (TMR2H:TMR2L) are loaded into the Timer2 reload registers (TMR2RLH:TMR2RLL) and the TF2H flag is set. By recording the difference between two successive timer capture values, the LFO clock frequency can be determined with respect to the Timer2 clock. The Timer2 clock should be much faster than the LFO to achieve an accurate reading. CKCON TTTTTTSS 3 3 2 2 1 0CC T2XCLK MMMMMMAA HLHL 1 0 SYSCLK / 12 0 0 TR2 TCLK TMR2L TMR2H External Clock / 8 1 SYSCLK 1 Capture Low-Frequency TF2CEN TMR2RLL TMR2RLH TF2H Interrupt Oscillator TF2L N TF2LEN C 2 TF2CEN R T2SPLIT M TR2 T T2XCLK Figure 31.6. Timer 2 Low-Frequency Oscillation Capture Mode Block Diagram Rev. 1.2 255

C8051F39x/37x SFR Definition 31.9. TMR2CN: Timer 2 Control Bit 7 6 5 4 3 2 1 0 Name TF2H TF2L TF2LEN TF2CEN T2SPLIT TR2 T2XCLK Type R/W R/W R/W R/W R/W R/W R R/W Reset 0 0 0 0 0 0 0 0 SFR Address=0xC8; SFR Page=0; Bit-Addressable Bit Name Function 7 TF2H Timer2 High Byte Overflow Flag. Set by hardware when the Timer2 high byte overflows from 0xFF to 0x00. In 16bit mode, this will occur when Timer2 overflows from 0xFFFF to 0x0000. When the Timer2 interrupt is enabled, setting this bit causes the CPU to vector to the Timer2 interrupt service routine. This bit is not automatically cleared by hardware. 6 TF2L Timer2 Low Byte Overflow Flag. Set by hardware when the Timer2 low byte overflows from 0xFF to 0x00. TF2L will be set when the low byte overflows regardless of the Timer2 mode. This bit is not auto- matically cleared by hardware. 5 TF2LEN Timer2 Low Byte Interrupt Enable. When set to 1, this bit enables Timer2 Low Byte interrupts. If Timer2 interrupts are also enabled, an interrupt will be generated when the low byte of Timer2 overflows. 4 TF2CEN Timer2 Low-Frequency Oscillator Capture Enable. When set to 1, this bit enables Timer2 Low-Frequency Oscillator Capture Mode. If TF2CEN is set and Timer2 interrupts are enabled, an interrupt will be generated on a falling edge of the low-frequency oscillator output, and the current 16-bit timer value in TMR2H:TMR2L will be copied to TMR2RLH:TMR2RLL. 3 T2SPLIT Timer2 Split Mode Enable. When this bit is set, Timer2 operates as two 8-bit timers with auto-reload. 0: Timer2 operates in 16-bit auto-reload mode. 1: Timer2 operates as two 8-bit auto-reload timers. 2 TR2 Timer2 Run Control. Timer2 is enabled by setting this bit to 1. In 8-bit mode, this bit enables/disables TMR2H only; TMR2L is always enabled in split mode. 1 Unused Unused. Read=0b; Write=Don’t Care 0 T2XCLK Timer2 External Clock Select. This bit selects the external clock source for Timer2. If Timer2 is in 8-bit mode, this bit selects the external oscillator clock source for both timer bytes. However, the Timer2 Clock Select bits (T2MH and T2ML in register CKCON) may still be used to select between the external clock and the system clock for either timer. 0: Timer2 clock is the system clock divided by 12. 1: Timer2 clock is the external clock divided by 8 (synchronized with SYSCLK). 256 Rev. 1.2

C8051F39x/37x SFR Definition 31.10. TMR2RLL: Timer 2 Reload Register Low Byte Bit 7 6 5 4 3 2 1 0 Name TMR2RLL[7:0] Type R/W Reset 0 0 0 0 0 0 0 0 SFR Address=0xCA; SFR Page=0 Bit Name Function 7:0 TMR2RLL[7:0] Timer 2 Reload Register Low Byte. TMR2RLL holds the low byte of the reload value for Timer 2. SFR Definition 31.11. TMR2RLH: Timer 2 Reload Register High Byte Bit 7 6 5 4 3 2 1 0 Name TMR2RLH[7:0] Type R/W Reset 0 0 0 0 0 0 0 0 SFR Address=0xCB; SFR Page=0 Bit Name Function 7:0 TMR2RLH[7:0] Timer 2 Reload Register High Byte. TMR2RLH holds the high byte of the reload value for Timer 2. SFR Definition 31.12. TMR2L: Timer 2 Low Byte Bit 7 6 5 4 3 2 1 0 Name TMR2L[7:0] Type R/W Reset 0 0 0 0 0 0 0 0 SFR Address=0xCC; SFR Page=0 Bit Name Function 7:0 TMR2L[7:0] Timer 2 Low Byte. In 16-bit mode, the TMR2L register contains the low byte of the 16-bit Timer 2. In 8-bit mode, TMR2L contains the 8-bit low byte timer value. Rev. 1.2 257

C8051F39x/37x SFR Definition 31.13. TMR2H Timer 2 High Byte Bit 7 6 5 4 3 2 1 0 Name TMR2H[7:0] Type R/W Reset 0 0 0 0 0 0 0 0 SFR Address=0xCD; SFR Page=0 Bit Name Function 7:0 TMR2H[7:0] Timer 2 Low Byte. In 16-bit mode, the TMR2H register contains the high byte of the 16-bit Timer 2. In 8-bit mode, TMR2H contains the 8-bit high byte timer value. 258 Rev. 1.2

C8051F39x/37x 31.3. Timer 3 Timer 3 is a 16-bit timer formed by two 8-bit SFRs: TMR3L (low byte) and TMR3H (high byte). Timer 3 may operate in 16-bit auto-reload mode or (split) 8-bit auto-reload mode. The T3SPLIT bit (TMR3CN.3) defines the Timer3 operation mode. Timer 3 may be clocked by the system clock, the system clock divided by 12, the external oscillator source divided by 8, or the internal low-frequency oscillator divided by 8. The external clock mode is ideal for real- time clock (RTC) functionality, where the internal high-frequency oscillator drives the system clock while Timer 3 is clocked by an external oscillator source. Note that the external oscillator source divided by 8 and the LFO source divided by 8 are synchronized with the system clock when in all operating modes except suspend. When the internal oscillator is placed in suspend mode, The external clock/8 signal or the LFO/8 output can directly drive the timer. This allows the use of an external clock or the LFO to wake up the device from suspend mode. The timer will continue to run in suspend mode and count up. When the timer overflow occurs, the device will wake from suspend mode, and begin executing code again. The timer value may be set prior to entering suspend, to overflow in the desired amount of time (number of clocks) to wake the device. If a wake-up source other than the timer wakes the device from suspend mode, it may take up to three timer clocks before the timer registers can be read or written. During this time, the STSYNC bit in register OSCICN will be set to 1, to indicate that it is not safe to read or write the timer reg- isters. Important Note: In internal LFO/8 mode, the divider for the internal LFO must be set to 1 for proper functionality. The timer will not operate if the LFO divider is not set to 1. 31.3.1. 16-bit Timer with Auto-Reload When T3SPLIT (TMR3CN.3) is zero, Timer 3 operates as a 16-bit timer with auto-reload. Timer 3 can be clocked by SYSCLK, SYSCLK divided by 12, or the external oscillator clock source divided by 8. As the 16-bit timer register increments and overflows from 0xFFFF to 0x0000, the 16-bit value in the Timer 3 reload registers (TMR3RLH and TMR3RLL) is loaded into the Timer 3 register as shown in Figure31.7, and the Timer 3 High Byte Overflow Flag (TMR3CN.7) is set. If Timer 3 interrupts are enabled (if EIE1.7 is set), an interrupt will be generated on each Timer 3 overflow. Additionally, if Timer 3 interrupts are enabled and the TF3LEN bit is set (TMR3CN.5), an interrupt will be generated each time the lower 8 bits (TMR3L) overflow from 0xFF to 0x00. CKCON T3XCLK[1:0] TTTTTTSS 3 3 2 2 1 0CC MMMMMMAA HLHL 1 0 SYSCLK / 12 00 To ADC External Clock / 8 01 0 TR3 TCLK TMR3L TMR3H TF3H Interrupt TF3L Internal LFO / 8 11 1 3CN TTFF33CLEENN R T3SPLIT M TR3 SYSCLK T T3XCLK1 T3XCLK0 TMR3RLL TMR3RLH Reload Figure 31.7. Timer 3 16-Bit Mode Block Diagram Rev. 1.2 259

C8051F39x/37x 31.3.2. 8-bit Timers with Auto-Reload When T3SPLIT is set, Timer 3 operates as two 8-bit timers (TMR3H and TMR3L). Both 8-bit timers oper- ate in auto-reload mode as shown in Figure31.8. TMR3RLL holds the reload value for TMR3L; TMR3RLH holds the reload value for TMR3H. The TR3 bit in TMR3CN handles the run control for TMR3H. TMR3L is always running when configured for 8-bit Mode. Each 8-bit timer may be configured to use SYSCLK, SYSCLK divided by 12, the external oscillator clock source divided by 8, or the internal Low-frequency Oscillator. The Timer 3 Clock Select bits (T3MH and T3ML in CKCON) select either SYSCLK or the clock defined by the Timer 3 External Clock Select bits (T3XCLK[1:0] in TMR3CN), as follows: T3MH T3XCLK[1:0] TMR3H Clock T3ML T3XCLK[1:0] TMR3L Clock Source Source 0 00 SYSCLK / 12 0 00 SYSCLK / 12 0 01 External Clock / 8 0 01 External Clock / 8 0 10 Reserved 0 10 Reserved 0 11 Internal LFO 0 11 Internal LFO 1 X SYSCLK 1 X SYSCLK The TF3H bit is set when TMR3H overflows from 0xFF to 0x00; the TF3L bit is set when TMR3L overflows from 0xFF to 0x00. When Timer 3 interrupts are enabled, an interrupt is generated each time TMR3H over- flows. If Timer 3 interrupts are enabled and TF3LEN (TMR3CN.5) is set, an interrupt is generated each time either TMR3L or TMR3H overflows. When TF3LEN is enabled, software must check the TF3H and TF3L flags to determine the source of the Timer 3 interrupt. The TF3H and TF3L interrupt flags are not cleared by hardware and must be manually cleared by software. CKCON TTTTTTSS T3XCLK[1:0] 332210CC MMMMMMAA Reload HLHL 10 TMR3RLH SYSCLK / 12 00 0 External Clock / 8 01 TCLK TR3 TMR3H TF3H Interrupt TF3L Internal LFO / 8 11 1 TF3LEN N TF3CEN C T3SPLIT Reload R3 TR3 TMR3RLL M T3XCLK1 SYSCLK T T3XCLK0 1 TCLK TMR3L To ADC 0 Figure 31.8. Timer 3 8-Bit Mode Block Diagram 260 Rev. 1.2

C8051F39x/37x 31.3.3. Low-Frequency Oscillator (LFO) Capture Mode The Low-Frequency Oscillator Capture Mode allows the LFO clock to be measured against the system clock or an external oscillator source. Timer3 can be clocked from the system clock, the system clock divided by 12, or the external oscillator divided by 8, depending on the T3ML (CKCON.6), and T3XCLK[1:0] settings. Setting TF3CEN to 1 enables the LFO Capture Mode for Timer3. In this mode, T3SPLIT should be set to 0, as the full 16-bit timer is used. Upon a falling edge of the low-frequency oscillator, the contents of Timer3 (TMR3H:TMR3L) are loaded into the Timer3 reload registers (TMR3RLH:TMR3RLL) and the TF3H flag is set. By recording the difference between two successive timer capture values, the LFO clock frequency can be determined with respect to the Timer3 clock. The Timer3 clock should be much faster than the LFO to achieve an accurate reading. This means that the LFO/8 should not be selected as the timer clock source in this mode. CKCON TTTTTTSS 3 3 2 2 1 0CC T3XCLK[1:0] MMMMMMAA HLHL 1 0 SYSCLK / 12 00 0 TR3 TCLK TMR3L TMR3H External Clock / 8 01 SYSCLK 1 Capture Low-Frequency TF3CEN TMR3RLL TMR3RLH TF3H Interrupt Oscillator TF3L N TF3LEN C 3 TF3CEN R T3SPLIT M TR3 T T3XCLK1 T3XCLK0 Figure 31.9. Timer 3 Low-Frequency Oscillation Capture Mode Block Diagram Rev. 1.2 261

C8051F39x/37x SFR Definition 31.14. TMR3CN: Timer 3 Control Bit 7 6 5 4 3 2 1 0 Name TF3H TF3L TF3LEN TF3CEN T3SPLIT TR3 T3XCLK[1:0] Type R/W R/W R/W R/W R/W R/W R/W Reset 0 0 0 0 0 0 0 0 SFR Address=0x91; SFR Page=0 Bit Name Function 7 TF3H Timer3 High Byte Overflow Flag. Set by hardware when the Timer3 high byte overflows from 0xFF to 0x00. In 16bit mode, this will occur when Timer3 overflows from 0xFFFF to 0x0000. When the Timer3 interrupt is enabled, setting this bit causes the CPU to vector to the Timer3 interrupt service routine. This bit is not automatically cleared by hardware. 6 TF3L Timer3 Low Byte Overflow Flag. Set by hardware when the Timer3 low byte overflows from 0xFF to 0x00. TF3L will be set when the low byte overflows regardless of the Timer3 mode. This bit is not automatically cleared by hardware. 5 TF3LEN Timer3 Low Byte Interrupt Enable. When set to 1, this bit enables Timer3 Low Byte interrupts. If Timer3 interrupts are also enabled, an interrupt will be generated when the low byte of Timer3 overflows. 4 TF3CEN Timer3 Low-Frequency Oscillator Capture Enable. When set to 1, this bit enables Timer3 Low-Frequency Oscillator Capture Mode. If TF3CEN is set and Timer3 interrupts are enabled, an interrupt will be generated on a falling edge of the low-frequency oscillator output, and the current 16-bit timer value in TMR3H:TMR3L will be copied to TMR3RLH:TMR3RLL. 3 T3SPLIT Timer3 Split Mode Enable. When this bit is set, Timer3 operates as two 8-bit timers with auto-reload. 0: Timer3 operates in 16-bit auto-reload mode. 1: Timer3 operates as two 8-bit auto-reload timers. 2 TR3 Timer3 Run Control. Timer3 is enabled by setting this bit to 1. In 8-bit mode, this bit enables/disables TMR3H only; TMR3L is always enabled in split mode. 1:0 T3XCLK[1:0] Timer3 External Clock Select. This bit selects the “external” clock source for Timer3. If Timer3 is in 8-bit mode, this bit selects the external oscillator clock source for both timer bytes. However, the Timer3 Clock Select bits (T3MH and T3ML in register CKCON) may still be used to select between the external clock and the system clock for either timer. 00: System clock divided by 12. 01: External clock divided by 8 (synchronized with SYSCLK when not in suspend). 10: Reserved. 11: Internal LFO/8 (synchronized with SYSCLK when not in suspend). 262 Rev. 1.2

C8051F39x/37x SFR Definition 31.15. TMR3RLL: Timer 3 Reload Register Low Byte Bit 7 6 5 4 3 2 1 0 Name TMR3RLL[7:0] Type R/W Reset 0 0 0 0 0 0 0 0 SFR Address=0x92; SFR Page=0 Bit Name Function 7:0 TMR3RLL[7:0] Timer 3 Reload Register Low Byte. TMR3RLL holds the low byte of the reload value for Timer 3. SFR Definition 31.16. TMR3RLH: Timer 3 Reload Register High Byte Bit 7 6 5 4 3 2 1 0 Name TMR3RLH[7:0] Type R/W Reset 0 0 0 0 0 0 0 0 SFR Address=0x93; SFR Page=0 Bit Name Function 7:0 TMR3RLH[7:0] Timer 3 Reload Register High Byte. TMR3RLH holds the high byte of the reload value for Timer 3. SFR Definition 31.17. TMR3L: Timer 3 Low Byte Bit 7 6 5 4 3 2 1 0 Name TMR3L[7:0] Type R/W Reset 0 0 0 0 0 0 0 0 SFR Address=0x94; SFR Page=0 Bit Name Function 7:0 TMR3L[7:0] Timer 3 Low Byte. In 16-bit mode, the TMR3L register contains the low byte of the 16-bit Timer 3. In 8-bit mode, TMR3L contains the 8-bit low byte timer value. Rev. 1.2 263

C8051F39x/37x SFR Definition 31.18. TMR3H Timer 3 High Byte Bit 7 6 5 4 3 2 1 0 Name TMR3H[7:0] Type R/W Reset 0 0 0 0 0 0 0 0 SFR Address=0x95; SFR Page=0 Bit Name Function 7:0 TMR3H[7:0] Timer 3 High Byte. In 16-bit mode, the TMR3H register contains the high byte of the 16-bit Timer 3. In 8-bit mode, TMR3H contains the 8-bit high byte timer value. 264 Rev. 1.2

C8051F39x/37x 31.4. Timer 4 Timer 4 is a 16-bit timer formed by two 8-bit SFRs: TMR4L (low byte) and TMR4H (high byte). Timer 4 may operate in 16-bit auto-reload mode or (split) 8-bit auto-reload mode. The T4SPLIT bit (TMR4CN.3) defines Timer4 may be clocked by the system clock, the system clock divided by 12, or the external oscillator source divided by 8. Note that the external oscillator source divided by 8 is synchronized with the system clock. 31.4.1. 16-bit Timer with Auto-Reload When T4SPLIT (TMR4CN.3) is zero, Timer 4 operates as a 16-bit timer with auto-reload. Timer 4 can be clocked by SYSCLK, SYSCLK divided by 12, or the external oscillator clock source divided by 8. As the 16-bit timer register increments and overflows from 0xFFFF to 0x0000, the 16-bit value in the Timer 4 reload registers (TMR4RLH and TMR4RLL) is loaded into the Timer 4 register as shown in Figure31.10, and the Timer 4 High Byte Overflow Flag (TMR4CN.7) is set. If Timer 4 interrupts are enabled (if EIE1.7 is set), an interrupt will be generated on each Timer 4 overflow. Additionally, if Timer 4 interrupts are enabled and the TF4LEN bit is set (TMR4CN.5), an interrupt will be generated each time the lower 8 bits (TMR4L) overflow from 0xFF to 0x00. CKCON1 TTTT 5544 T4XCLK MMMM HLHL SYSCLK / 12 0 To ADC 0 External Clock / 8 1 TR4 TCLK TMR4L TMR4H TTFF44HL Interrupt N TF4LEN C SYSCLK 1 4 T4CE R T4SPLIT M TR4 T T4CSS T4XCLK TMR4RLL TMR4RLH Reload Figure 31.10. Timer 4 16-Bit Mode Block Diagram Rev. 1.2 265

C8051F39x/37x 31.4.2. 8-bit Timers with Auto-Reload When T4SPLIT is 1 and T4CE=0, Timer 4 operates as two 8-bit timers (TMR4H and TMR4L). Both 8-bit timers operate in auto-reload mode as shown in Figure31.11. TMR4RLL holds the reload value for TMR4L; TMR4RLH holds the reload value for TMR4H. The TR4 bit in TMR4CN handles the run control for TMR4H. TMR4L is always running when configured for 8-bit Mode. Each 8-bit timer may be configured to use SYSCLK, SYSCLK divided by 12, or the external oscillator clock source divided by 8. The Timer 4 Clock Select bits (T4MH and T4ML in CKCON1) select either SYSCLK or the clock defined by the Timer 4 External Clock Select bit (T4XCLK in TMR4CN), as follows: T4MH T4XCLK TMR4H Clock Source T4ML T4XCLK TMR4L Clock Source 0 0 SYSCLK/12 0 0 SYSCLK/12 0 1 External Clock/8 0 1 External Clock/8 1 X SYSCLK 1 X SYSCLK The TF4H bit is set when TMR4H overflows from 0xFF to 0x00; the TF4L bit is set when TMR4L overflows from 0xFF to 0x00. When Timer 4 interrupts are enabled, an interrupt is generated each time TMR4H over- flows. If Timer 4 interrupts are enabled and TF4LEN (TMR4CN.5) is set, an interrupt is generated each time either TMR4L or TMR4H overflows. When TF4LEN is enabled, software must check the TF4H and TF4L flags to determine the source of the Timer 4 interrupt. The TF4H and TF4L interrupt flags are not cleared by hardware and must be manually cleared by software. CKCON1 T4XCLK TTTT 5544 MMMM Reload HLHL TMR4RLH SYSCLK / 12 0 To ADC 0 External Clock / 8 1 TCLK TR4 TMR4H TF4H Interrupt TF4L 1 TF4LEN N T4CE C T4SPLIT Reload R4 TR4 TMR4RLL M T4CSS SYSCLK T T4XCLK 1 TCLK TMR4L 0 Figure 31.11. Timer 4 8-Bit Mode Block Diagram 266 Rev. 1.2

C8051F39x/37x SFR Definition 31.19. TMR4CN: Timer 4 Control Bit 7 6 5 4 3 2 1 0 Name TF4H TF4L TF4LEN T4SPLIT TR4 T4XCLK Type R/W R/W R/W R R/W R/W R R/W Reset 0 0 0 0 0 0 0 0 SFR Address=0x91; SFR Page=F Bit Name Function 7 TF4H Timer4 High Byte Overflow Flag. Set by hardware when the Timer4 high byte overflows from 0xFF to 0x00. In 16bit mode, this will occur when Timer4 overflows from 0xFFFF to 0x0000. When the Timer4 interrupt is enabled, setting this bit causes the CPU to vector to the Timer4 interrupt service routine. This bit is not automatically cleared by hardware. 6 TF4L Timer4 Low Byte Overflow Flag. Set by hardware when the Timer4 low byte overflows from 0xFF to 0x00. TF4L will be set when the low byte overflows regardless of the Timer4 mode. This bit is not automatically cleared by hardware. 5 TF4LEN Timer4 Low Byte Interrupt Enable. When set to 1, this bit enables Timer4 Low Byte interrupts. If Timer4 interrupts are also enabled, an interrupt will be generated when the low byte of Timer4 overflows. 4 Unused Read=0b; Write=don’t care. 3 T4SPLIT Timer4 Split Mode Enable. When this bit is set, Timer4 operates as two 8-bit timers with auto- reload. 0: Timer4 operates in 16-bit auto-reload mode. 1: Timer4 operates as two 8-bit auto-reload timers. 2 TR4 Timer4 Run Control. Timer4 is enabled by setting this bit to 1. In 8-bit mode, this bit enables/ disables TMR4H only; TMR4L is always enabled in split mode. 1 Unused Read=0b; Write=don’t care. 0 T4XCLK Timer4 External Clock Select. This bit selects the external clock source for Timer4. However, the Timer4 Clock Select bits (T4MH and T4ML in register CKCON1) may still be used to select between the external clock and the system clock for either timer. 0: Timer4 clock is the system clock divided by 12. 1: Timer4 clock is the external clock divided by 8 (synchronized with SYSCLK). Rev. 1.2 267

C8051F39x/37x SFR Definition 31.20. TMR4RLL: Timer 4 Reload Register Low Byte Bit 7 6 5 4 3 2 1 0 Name TMR4RLL[7:0] Type R/W Reset 0 0 0 0 0 0 0 0 SFR Address=0x92; SFR Page=F Bit Name Function 7:0 TMR4RLL[7:0] Timer 4 Reload Register Low Byte. TMR4RLL holds the low byte of the reload value for Timer 4. SFR Definition 31.21. TMR4RLH: Timer 4 Reload Register High Byte Bit 7 6 5 4 3 2 1 0 Name TMR4RLH[7:0] Type R/W Reset 0 0 0 0 0 0 0 0 SFR Address=0x93; SFR Page=F Bit Name Function 7:0 TMR4RLH[7:0] Timer 4 Reload Register High Byte. TMR4RLH holds the high byte of the reload value for Timer 4. SFR Definition 31.22. TMR4L: Timer 4 Low Byte Bit 7 6 5 4 3 2 1 0 Name TMR4L[7:0] Type R/W Reset 0 0 0 0 0 0 0 0 SFR Address=0x94; SFR Page=F Bit Name Function 7:0 TMR4L[7:0] Timer 4 Low Byte. In 16-bit mode, the TMR4L register contains the low byte of the 16-bit Timer 4. In 8-bit mode, TMR4L contains the 8-bit low byte timer value. 268 Rev. 1.2

C8051F39x/37x SFR Definition 31.23. TMR4H Timer 4 High Byte Bit 7 6 5 4 3 2 1 0 Name TMR4H[7:0] Type R/W Reset 0 0 0 0 0 0 0 0 SFR Address=0x95; SFR Page=F Bit Name Function 7:0 TMR4H[7:0] Timer 4 High Byte. In 16-bit mode, the TMR4H register contains the high byte of the 16-bit Timer 4. In 8-bit mode, TMR4H contains the 8-bit high byte timer value. Rev. 1.2 269

C8051F39x/37x 31.5. Timer 5 Timer 5 is a 16-bit timer formed by two 8-bit SFRs: TMR5L (low byte) and TMR5H (high byte). Timer 5 may operate in 16-bit auto-reload mode or (split) 8-bit auto-reload mode. The T5SPLIT bit (TMR5CN.3) defines Timer5 may be clocked by the system clock, the system clock divided by 12, or the external oscillator source divided by 8. Note that the external oscillator source divided by 8 is synchronized with the system clock. 31.5.1. 16-bit Timer with Auto-Reload When T5SPLIT (TMR5CN.3) is zero, Timer 5 operates as a 16-bit timer with auto-reload. Timer 5 can be clocked by SYSCLK, SYSCLK divided by 12, or the external oscillator clock source divided by 8. As the 16-bit timer register increments and overflows from 0xFFFF to 0x0000, the 16-bit value in the Timer 5 reload registers (TMR5RLH and TMR5RLL) is loaded into the Timer 5 register as shown in Figure31.12, and the Timer 5 High Byte Overflow Flag (TMR5CN.7) is set. If Timer 5 interrupts are enabled (if EIE1.7 is set), an interrupt will be generated on each Timer 5 overflow. Additionally, if Timer 5 interrupts are enabled and the TF5LEN bit is set (TMR5CN.5), an interrupt will be generated each time the lower 8 bits (TMR5L) overflow from 0xFF to 0x00. CKCON1 TTTT 5544 T5XCLK MMMM HLHL SYSCLK / 12 0 To ADC 0 External Clock / 8 1 TR5 TCLK TMR5L TMR5H TTFF55HL Interrupt N TF5LEN C SYSCLK 1 5 T5CE R T5SPLIT M TR5 T T5CSS T5XCLK TMR5RLL TMR5RLH Reload Figure 31.12. Timer 5 16-Bit Mode Block Diagram 270 Rev. 1.2

C8051F39x/37x 31.5.2. 8-bit Timers with Auto-Reload When T5SPLIT is 1 and T5CE=0, Timer 5 operates as two 8-bit timers (TMR5H and TMR5L). Both 8-bit timers operate in auto-reload mode as shown in Figure31.13. TMR5RLL holds the reload value for TMR5L; TMR5RLH holds the reload value for TMR5H. The TR5 bit in TMR5CN handles the run control for TMR5H. TMR5L is always running when configured for 8-bit Mode. Each 8-bit timer may be configured to use SYSCLK, SYSCLK divided by 12, or the external oscillator clock source divided by 8. The Timer 5 Clock Select bits (T5MH and T5ML in CKCON1) select either SYSCLK or the clock defined by the Timer 5 External Clock Select bit (T5XCLK in TMR5CN), as follows: T5MH T5XCLK TMR5H Clock Source T5ML T5XCLK TMR5L Clock Source 0 0 SYSCLK/12 0 0 SYSCLK/12 0 1 External Clock/8 0 1 External Clock/8 1 X SYSCLK 1 X SYSCLK The TF5H bit is set when TMR5H overflows from 0xFF to 0x00; the TF5L bit is set when TMR5L overflows from 0xFF to 0x00. When Timer 5 interrupts are enabled, an interrupt is generated each time TMR5H over- flows. If Timer 5 interrupts are enabled and TF5LEN (TMR5CN.5) is set, an interrupt is generated each time either TMR5L or TMR5H overflows. When TF5LEN is enabled, software must check the TF5H and TF5L flags to determine the source of the Timer 5 interrupt. The TF5H and TF5L interrupt flags are not cleared by hardware and must be manually cleared by software. CKCON1 TTTT T5XCLK 5544 MMMM Reload HLHL TMR5RLH SYSCLK / 12 0 To ADC 0 External Clock / 8 1 TCLK TR5 TMR5H TF5H Interrupt TF5L 1 TF5LEN N T5CE C T5SPLIT Reload R5 TR5 TMR5RLL M T5CSS SYSCLK T T5XCLK 1 TCLK TMR5L 0 Figure 31.13. Timer 5 8-Bit Mode Block Diagram Rev. 1.2 271

C8051F39x/37x SFR Definition 31.24. TMR5CN: Timer 5 Control Bit 7 6 5 4 3 2 1 0 Name TF5H TF5L TF5LEN T5SPLIT TR5 T5XCLK Type R/W R/W R/W R R/W R/W R R/W Reset 0 0 0 0 0 0 0 0 SFR Address=0xC8; SFR Page=F; Bit-Addressable Bit Name Function 7 TF5H Timer5 High Byte Overflow Flag. Set by hardware when the Timer5 high byte overflows from 0xFF to 0x00. In 16bit mode, this will occur when Timer5 overflows from 0xFFFF to 0x0000. When the Timer5 interrupt is enabled, setting this bit causes the CPU to vector to the Timer5 interrupt service routine. This bit is not auto- matically cleared by hardware. 6 TF5L Timer5 Low Byte Overflow Flag. Set by hardware when the Timer5 low byte overflows from 0xFF to 0x00. TF5L will be set when the low byte overflows regardless of the Timer5 mode. This bit is not automatically cleared by hardware. 5 TF5LEN Timer5 Low Byte Interrupt Enable. When set to 1, this bit enables Timer5 Low Byte interrupts. If Timer5 interrupts are also enabled, an interrupt will be generated when the low byte of Timer5 overflows. 4 Unused Read=0b; Write=don’t care. 3 T5SPLIT Timer5 Split Mode Enable. When this bit is set, Timer5 operates as two 8-bit timers with auto-reload. 0: Timer5 operates in 16-bit auto-reload mode. 1: Timer5 operates as two 8-bit auto-reload timers. 2 TR5 Timer5 Run Control. Timer5 is enabled by setting this bit to 1. In 8-bit mode, this bit enables/ disables TMR5H only; TMR5L is always enabled in split mode. 1 Unused Read=0b; Write=don’t care. 0 T5XCLK Timer5 External Clock Select. This bit selects the external clock source for Timer5. However, the Timer5 Clock Select bits (T5MH and T5ML in register CKCON1) may still be used to select between the external clock and the system clock for either timer. 0: Timer5 clock is the system clock divided by 12. 1: Timer5 clock is the external clock divided by 8 (synchronized with SYSCLK). 272 Rev. 1.2

C8051F39x/37x SFR Definition 31.25. TMR5RLL: Timer 5 Reload Register Low Byte Bit 7 6 5 4 3 2 1 0 Name TMR5RLL[7:0] Type R/W Reset 0 0 0 0 0 0 0 0 SFR Address=0xCA; SFR Page=F Bit Name Function 7:0 TMR5RLL[7:0] Timer 5 Reload Register Low Byte. TMR5RLL holds the low byte of the reload value for Timer 5. SFR Definition 31.26. TMR5RLH: Timer 5 Reload Register High Byte Bit 7 6 5 4 3 2 1 0 Name TMR5RLH[7:0] Type R/W Reset 0 0 0 0 0 0 0 0 SFR Address=0xCB; SFR Page=F Bit Name Function 7:0 TMR5RLH[7:0] Timer 5 Reload Register High Byte. TMR5RLH holds the high byte of the reload value for Timer 5. SFR Definition 31.27. TMR5L: Timer 5 Low Byte Bit 7 6 5 4 3 2 1 0 Name TMR5L[7:0] Type R/W Reset 0 0 0 0 0 0 0 0 SFR Address=0xCC; SFR Page=F Bit Name Function 7:0 TMR5L[7:0] Timer 5 Low Byte. In 16-bit mode, the TMR5L register contains the low byte of the 16-bit Timer 5. In 8-bit mode, TMR5L contains the 8-bit low byte timer value. Rev. 1.2 273

C8051F39x/37x SFR Definition 31.28. TMR5H Timer 5 High Byte Bit 7 6 5 4 3 2 1 0 Name TMR5H[7:0] Type R/W Reset 0 0 0 0 0 0 0 0 SFR Address=0xCD; SFR Page=F Bit Name Function 7:0 TMR5H[7:0] Timer 5 High Byte. In 16-bit mode, the TMR5H register contains the high byte of the 16- bit Timer 5. In 8-bit mode, TMR5H contains the 8-bit high byte timer value. 274 Rev. 1.2

C8051F39x/37x 32. Programmable Counter Array The Programmable Counter Array (PCA0) provides enhanced timer functionality while requiring less CPU intervention than the standard 8051 counter/timers. The PCA consists of a dedicated 16-bit counter/timer and three 16-bit capture/compare modules. Each capture/compare module has its own associated I/O line (CEXn) which is routed through the Crossbar to Port I/O when enabled. The counter/timer is driven by a programmable timebase that can select between seven sources: system clock, system clock divided by four, system clock divided by twelve, the external oscillator clock source divided by 8, low frequency oscil- lator divided by 8, Timer 0 overflows, or an external clock signal on the ECI input pin. Each capture/com- pare module may be configured to operate independently in one of six modes: Edge-Triggered Capture, Software Timer, High-Speed Output, Frequency Output, 8 to 11-Bit PWM, or 16-Bit PWM (each mode is described in Section “32.3.Capture/Compare Modules” on page278). The external oscillator clock option is ideal for real-time clock (RTC) functionality, allowing the PCA to be clocked by a precision external oscil- lator while the internal oscillator drives the system clock. The PCA is configured and controlled through the system controller's Special Function Registers. The PCA block diagram is shown in Figure32.1 Important Note: The PCA Module 2 may be used as a watchdog timer (WDT), and is enabled in this mode following a system reset. Access to certain PCA registers is restricted while WDT mode is enabled. See Section 32.4 for details. SYSCLK/12 SYSCLK/4 Timer 0 Overflow PCA 16-Bit Counter/Timer ECI CLOCK SYSCLK MUX External Clock/8 LFO/8 Capture/Compare Capture/Compare Capture/Compare Module 0 Module 1 Module 2 / WDT E C C C C E E E I X X X 0 1 2 Crossbar Port I/O Figure 32.1. PCA Block Diagram Rev. 1.2 275

C8051F39x/37x 32.1. PCA Counter/Timer The 16-bit PCA counter/timer consists of two 8-bit SFRs: PCA0L and PCA0H. PCA0H is the high byte (MSB) of the 16-bit counter/timer and PCA0L is the low byte (LSB). Reading PCA0L automatically latches the value of PCA0H into a “snapshot” register; the following PCA0H read accesses this “snapshot” register. Reading the PCA0L Register first guarantees an accurate reading of the entire 16-bit PCA0 counter. Reading PCA0H or PCA0L does not disturb the counter operation. The CPS2–CPS0 bits in the PCA0MD register select the timebase for the counter/timer as shown in Table32.1. When the counter/timer overflows from 0xFFFF to 0x0000, the Counter Overflow Flag (CF) in PCA0MD is set to logic1 and an interrupt request is generated if CF interrupts are enabled. Setting the ECF bit in PCA0MD to logic1 enables the CF flag to generate an interrupt request. The CF bit is not automatically cleared by hardware when the CPU vectors to the interrupt service routine, and must be cleared by soft- ware. Clearing the CIDL bit in the PCA0MD register allows the PCA to continue normal operation while the CPU is in Idle mode. Table 32.1. PCA Timebase Input Options CPS2 CPS1 CPS0 Timebase 0 0 0 System clock divided by 12 0 0 1 System clock divided by 4 0 1 0 Timer 0 overflow High-to-low transitions on ECI (max rate=system clock divided 0 1 1 by 4) 1 0 0 System clock 1 0 1 External oscillator source divided by 8* 1 1 0 Low frequency oscillator divided by 8* 1 1 1 Reserved Note: Synchronized with the system clock. IDLE PCA0MD PCA0CN CWW CCCE CC CCC I DD PPPC FR CCC DTL SSSF FFF LEC 210 210 To SFR Bus K PCA0L read Snapshot Register SYSCLK/12 000 SYSCLK/4 001 Timer 0 Overflow 010 ECI 011 0 PCA0H PCA0L Overflow To PCA Interrupt System 1 SYSCLK 100 CF External Clock/8 101 LFO/8 To PCA Modules 110 Figure 32.2. PCA Counter/Timer Block Diagram 276 Rev. 1.2

C8051F39x/37x 32.2. PCA0 Interrupt Sources Figure32.3 shows a diagram of the PCA interrupt tree. There are five independent event flags that can be used to generate a PCA0 interrupt. They are: the main PCA counter overflow flag (CF), which is set upon a 16-bit overflow of the PCA0 counter, an intermediate overflow flag (COVF), which can be set on an over- flow from the 8th, 9th, 10th, or 11th bit of the PCA0 counter, and the individual flags for each PCA channel (CCF0, CCF1, and CCF2), which are set according to the operation mode of that module. These event flags are always set when the trigger condition occurs. Each of these flags can be individually selected to generate a PCA0 interrupt, using the corresponding interrupt enable flag (ECF for CF, ECOV for COVF, and ECCFn for each CCFn). PCA0 interrupts must be globally enabled before any individual interrupt sources are recognized by the processor. PCA0 interrupts are globally enabled by setting the EA bit and the EPCA0 bit to logic 1. (for n = 0 to 2) PCA0CPMn PCA0CN PCA0MD PCA0PWM PECCMTPE CC CCC CWW CCCE AEC CC WCAAAOWC FR CCC IDD PPPC RCO LL MOPPTGMC FFF DTL SSSF SOV SS 1MPNnnnF 210 LEC 210 EVF EE 6nnn n K L LL n 10 PCA Counter/Timer 8, 9, Set 8, 9, 10, or 11 bit Operation 10 or 11-bit Overflow PCA Counter/Timer 16- 0 0 bit Overflow 1 ECCF0 1 EPCA0 EA PCA Module 0 0 0 0 Interrupt Priority (CCF0) 1 1 1 Decoder ECCF1 PCA Module 1 0 (CCF1) 1 ECCF2 PCA Module 2 0 (CCF2) 1 Figure 32.3. PCA Interrupt Block Diagram Rev. 1.2 277

C8051F39x/37x 32.3. Capture/Compare Modules Each module can be configured to operate independently in one of six operation modes: edge-triggered capture, software timer, high-speed output, frequency output, 8 to 11-bit pulse width modulator, or 16-bit pulse width modulator. Each module has Special Function Registers (SFRs) associated with it in the CIP- 51 system controller. These registers are used to exchange data with a module and configure the module's mode of operation. Table32.2 summarizes the bit settings in the PCA0CPMn and PCA0PWM registers used to select the PCA capture/compare module’s operating mode. Note that all modules set to use 8, 9, 10, or 11-bit PWM mode must use the same cycle length (8–11 bits). Setting the ECCFn bit in a PCA0CPMn register enables the module's CCFn interrupt. Table 32.2. PCA0CPM and PCA0PWM Bit Settings for PCA Capture/Compare Modules Operational Mode PCA0CPMn PCA0PWM Bit Number 7 6 5 4 3 2 1 0 7 6 5 4–2 1–0 Capture triggered by positive edge on CEXn X X 1 0 0 0 0 A 0 X B XXX XX Capture triggered by negative edge on CEXn X X 0 1 0 0 0 A 0 X B XXX XX Capture triggered by any transition on CEXn X X 1 1 0 0 0 A 0 X B XXX XX Software Timer X C 0 0 1 0 0 A 0 X B XXX XX High Speed Output X C 0 0 1 1 0 A 0 X B XXX XX Frequency Output X C 0 0 0 1 1 A 0 X B XXX XX 8-Bit Pulse Width Modulator (Note7) 0 C 0 0 E 0 1 A 0 X B XXX 00 9-Bit Pulse Width Modulator (Note7) 0 C 0 0 E 0 1 A D X B XXX 01 10-Bit Pulse Width Modulator (Note7) 0 C 0 0 E 0 1 A D X B XXX 10 11-Bit Pulse Width Modulator (Note7) 0 C 0 0 E 0 1 A D X B XXX 11 16-Bit Pulse Width Modulator 1 C 0 0 E 0 1 A 0 X B XXX XX Notes: 1. X=Don’t Care (no functional difference for individual module if 1 or 0). 2. A=Enable interrupts for this module (PCA interrupt triggered on CCFn set to 1). 3. B=Enable 8th, 9th, 10th or 11th bit overflow interrupt (Depends on setting of CLSEL[1:0]). 4. C=When set to 0, the digital comparator is off. For high speed and frequency output modes, the associated pin will not toggle. In any of the PWM modes, this generates a 0% duty cycle (output=0). 5. D=Selects whether the Capture/Compare register (0) or the Auto-Reload register (1) for the associated channel is accessed via addresses PCA0CPHn and PCA0CPLn. 6. E=When set, a match event will cause the CCFn flag for the associated channel to be set. 7. All modules set to 8, 9, 10 or 11-bit PWM mode use the same cycle length setting. 278 Rev. 1.2

C8051F39x/37x 32.3.1. Edge-triggered Capture Mode In this mode, a valid transition on the CEXn pin causes the PCA to capture the value of the PCA counter/ timer and load it into the corresponding module's 16-bit capture/compare register (PCA0CPLn and PCA0CPHn). The CAPPn and CAPNn bits in the PCA0CPMn register are used to select the type of transi- tion that triggers the capture: low-to-high transition (positive edge), high-to-low transition (negative edge), or either transition (positive or negative edge). When a capture occurs, the Capture/Compare Flag (CCFn) in PCA0CN is set to logic1. An interrupt request is generated if the CCFn interrupt for that module is enabled. The CCFn bit is not automatically cleared by hardware when the CPU vectors to the interrupt ser- vice routine, and must be cleared by software. If both CAPPn and CAPNn bits are set to logic1, then the state of the Port pin associated with CEXn can be read directly to determine whether a rising-edge or fall- ing-edge caused the capture. PCA Interrupt PCA0CPMn PCA0CN PECCMTPE WCAAAOWC CC CCC MOPPTGMC FR CCC 1MPNn n nF FFF 6 n n n n 2 1 0 n x x 0 0 0 x Fn) PCA0CPLn PCA0CPHn C C 0 o (t 1 CEXn Capture Port I/O Crossbar 0 1 PCA PCA0L PCA0H Timebase Figure 32.4. PCA Capture Mode Diagram Note: The CEXn input signal must remain high or low for at least 2system clock cycles to be recognized by the hardware. Rev. 1.2 279

C8051F39x/37x 32.3.2. Software Timer (Compare) Mode In Software Timer mode, the PCA counter/timer value is compared to the module's 16-bit capture/compare register (PCA0CPHn and PCA0CPLn). When a match occurs, the Capture/Compare Flag (CCFn) in PCA0CN is set to logic1. An interrupt request is generated if the CCFn interrupt for that module is enabled. The CCFn bit is not automatically cleared by hardware when the CPU vectors to the interrupt ser- vice routine, and must be cleared by software. Setting the ECOMn and MATn bits in the PCA0CPMn regis- ter enables Software Timer mode. Important Note About Capture/Compare Registers: When writing a 16-bit value to the PCA0 Capture/ Compare registers, the low byte should always be written first. Writing to PCA0CPLn clears the ECOMn bit to 0; writing to PCA0CPHn sets ECOMn to 1. Write to PCA0CPLn 0 Reset ENB Write to PCA0CPHn ENB PCA Interrupt 1 PCA0CPMn PECCMTPE PCA0CN WCAAAOWC CC CCC MOPPTGMC PCA0CPLn PCA0CPHn FR CCC 1MPNnnnF FFF 6nnn n 210 n x 0 0 0 0 x 0 Enable 16-bit Comparator Match 1 PCA PCA0L PCA0H Timebase Figure 32.5. PCA Software Timer Mode Diagram 280 Rev. 1.2

C8051F39x/37x 32.3.3. High-Speed Output Mode In High-Speed Output mode, a module’s associated CEXn pin is toggled each time a match occurs between the PCA Counter and the module's 16-bit capture/compare register (PCA0CPHn and PCA0CPLn). When a match occurs, the Capture/Compare Flag (CCFn) in PCA0CN is set to logic1. An interrupt request is generated if the CCFn interrupt for that module is enabled. The CCFn bit is not auto- matically cleared by hardware when the CPU vectors to the interrupt service routine, and must be cleared by software. Setting the TOGn, MATn, and ECOMn bits in the PCA0CPMn register enables the High- Speed Output mode. If ECOMn is cleared, the associated pin will retain its state, and not toggle on the next match event. Important Note About Capture/Compare Registers: When writing a 16-bit value to the PCA0 Capture/ Compare registers, the low byte should always be written first. Writing to PCA0CPLn clears the ECOMn bit to 0; writing to PCA0CPHn sets ECOMn to 1. Write to PCA0CPLn 0 ENB Reset PCA0CPMn Write to PCA0CPHn ENB PECCMTPE 1 WCAAAOWC MOPPTGMC 1MPNn n n F 6 n n n n n x 0 0 0 x PCA Interrupt PCA0CN CC CCC PCA0CPLn PCA0CPHn FR CCC FFF 2 1 0 0 Enable Match 16-bit Comparator 1 TOGn Toggle 0 CEXn Crossbar Port I/O 1 PCA PCA0L PCA0H Timebase Figure 32.6. PCA High-Speed Output Mode Diagram Rev. 1.2 281

C8051F39x/37x 32.3.4. Frequency Output Mode Frequency Output Mode produces a programmable-frequency square wave on the module’s associated CEXn pin. The capture/compare module high byte holds the number of PCA clocks to count before the out- put is toggled. The frequency of the square wave is then defined by Equation32.1. F F = -------------------P---C---A---------------- CEXn 2 PCA0CPHn Note: A value of 0x00 in the PCA0CPHn register is equal to 256 for this equation. Equation 32.1. Square Wave Frequency Output Where F is the frequency of the clock selected by the CPS2–0 bits in the PCA mode register, PCA PCA0MD. The lower byte of the capture/compare module is compared to the PCA counter low byte; on a match, n is toggled and the offset held in the high byte is added to the matched value in PCA0CPLn. Fre- quency Output Mode is enabled by setting the ECOMn, TOGn, and PWMn bits in the PCA0CPMn register. Note that the MATn bit should normally be set to 0 in this mode. If the MATn bit is set to 1, the CCFn flag for the channel will be set when the 16-bit PCA0 counter and the 16-bit capture/compare register for the channel are equal. Write to PCA0CPLn 0 Reset ENB PCA0CPMn Write to PECCMTPE PCA0CPHn ENB WCAAAOWC PCA0CPLn 8-bit Adder PCA0CPHn 1 MOPPTGMC 1MPNnnnF Adder 6nnn n Enable n TOGn x 0 0 0 x Toggle Enable 8-bit match 0 CEXn Crossbar Port I/O Comparator 1 PCA Timebase PCA0L Figure 32.7. PCA Frequency Output Mode 32.3.5. 8-bit, 9-bit, 10-bit and 11-bit Pulse Width Modulator Modes Each module can be used independently to generate a pulse width modulated (PWM) output on its associ- ated CEXn pin. The frequency of the output is dependent on the timebase for the PCA counter/timer, and the setting of the PWM cycle length (8, 9, 10 or 11-bits). For backwards-compatibility with the 8-bit PWM mode available on other devices, the 8-bit PWM mode operates slightly different than 9, 10 and 11-bit PWM modes. It is important to note that all channels configured for 8/9/10/11-bit PWM mode will use the same cycle length. It is not possible to configure one channel for 8-bit PWM mode and another for 11- bit mode (for example). However, other PCA channels can be configured to Pin Capture, High-Speed Out- put, Software Timer, Frequency Output, or 16-bit PWM mode independently. 282 Rev. 1.2

C8051F39x/37x 32.3.5.1. 8-bit Pulse Width Modulator Mode The duty cycle of the PWM output signal in 8-bit PWM mode is varied using the module's PCA0CPLn cap- ture/compare register. When the value in the low byte of the PCA counter/timer (PCA0L) is equal to the value in PCA0CPLn, the output on the CEXn pin will be set. When the count value in PCA0L overflows, the CEXn output will be reset (see Figure32.8). Also, when the counter/timer low byte (PCA0L) overflows from 0xFF to 0x00, PCA0CPLn is reloaded automatically with the value stored in the module’s capture/compare high byte (PCA0CPHn) without software intervention. Setting the ECOMn and PWMn bits in the PCA0CPMn register, and setting the CLSEL bits in register PCA0PWM to 00b enables 8-Bit Pulse Width Modulator mode. If the MATn bit is set to 1, the CCFn flag for the module will be set each time an 8-bit comparator match (rising edge) occurs. The COVF flag in PCA0PWM can be used to detect the overflow (falling edge), which will occur every 256 PCA clock cycles. The duty cycle for 8-Bit PWM Mode is given in Equation32.2. Important Note About Capture/Compare Registers: When writing a 16-bit value to the PCA0 Capture/ Compare registers, the low byte should always be written first. Writing to PCA0CPLn clears the ECOMn bit to 0; writing to PCA0CPHn sets ECOMn to 1. 256–PCA0CPHn Duty Cycle = --------------------------------------------------- 256 Equation 32.2. 8-Bit PWM Duty Cycle Using Equation32.2, the largest duty cycle is 100% (PCA0CPHn=0), and the smallest duty cycle is 0.39% (PCA0CPHn=0xFF). A 0% duty cycle may be generated by clearing the ECOMn bit to 0. Write to PCA0CPLn 0 Reset ENB PCA0CPHn Write to PCA0CPHn ENB 1 COVF PCA0PWM PCA0CPMn AEC CC PECCMTPE RCO LL WCAAAOWC PCA0CPLn SOV SS MOPPTGMC EVF EE 1MPNnnnF L LL 6nnn n 10 n 0 x 0 0 0 0 0 x 0 x Enable 8-bit match S SET Q CEXn Crossbar Port I/O Comparator R CLR Q PCA Timebase PCA0L Overflow Figure 32.8. PCA 8-Bit PWM Mode Diagram Rev. 1.2 283

C8051F39x/37x 32.3.5.2. 9/10/11-bit Pulse Width Modulator Mode The duty cycle of the PWM output signal in 9/10/11-bit PWM mode should be varied by writing to an “Auto- Reload” Register, which is dual-mapped into the PCA0CPHn and PCA0CPLn register locations. The data written to define the duty cycle should be right-justified in the registers. The auto-reload registers are accessed (read or written) when the bit ARSEL in PCA0PWM is set to 1. The capture/compare registers are accessed when ARSEL is set to 0. When the least-significant N bits of the PCA0 counter match the value in the associated module’s capture/ compare register (PCA0CPn), the output on CEXn is asserted high. When the counter overflows from the Nth bit, CEXn is asserted low (see Figure32.9). Upon an overflow from the Nth bit, the COVF flag is set, and the value stored in the module’s auto-reload register is loaded into the capture/compare register. The value of N is determined by the CLSEL bits in register PCA0PWM. The 9, 10 or 11-bit PWM mode is selected by setting the ECOMn and PWMn bits in the PCA0CPMn regis- ter, and setting the CLSEL bits in register PCA0PWM to the desired cycle length (other than 8-bits). If the MATn bit is set to 1, the CCFn flag for the module will be set each time a comparator match (rising edge) occurs. The COVF flag in PCA0PWM can be used to detect the overflow (falling edge), which will occur every 512 (9-bit), 1024 (10-bit) or 2048 (11-bit) PCA clock cycles. The duty cycle for 9/10/11-Bit PWM Mode is given in Equation32.2, where N is the number of bits in the PWM cycle. Important Note About PCA0CPHn and PCA0CPLn Registers: When writing a 16-bit value to the PCA0CPn registers, the low byte should always be written first. Writing to PCA0CPLn clears the ECOMn bit to 0; writing to PCA0CPHn sets ECOMn to 1. 2N–PCA0CPn Duty Cycle = -------------------------------------------- 2N Equation 32.3. 9, 10, and 11-Bit PWM Duty Cycle A 0% duty cycle may be generated by clearing the ECOMn bit to 0. Write to PCA0CPLn 0 R/W when Reset ENB ARSEL = 1 P(CAuAto0-CRePloHa:dL)n PCA0PWM AEC CC Write to (right-justified) RCO LL PCA0CPHn ENB SOV SS 1 EVF EE L LL PCA0CPMn 10 PECCMTPE R/W when x WCAAAOWC ARSEL = 0 (Capture/Compare) Set “N” bits: MOPPTGMC PCA0CPH:Ln 01 = 9 bits 1MPNnnnF (right-justified) 10 = 10 bits 6nnn n 11 = 11 bits n 0 0 0 x 0 x Enable N-bit Comparator match S SET Q CEXn Crossbar Port I/O R CLR Q PCA Timebase PCA0H:L Overflow of Nth Bit Figure 32.9. PCA 9, 10 and 11-Bit PWM Mode Diagram 284 Rev. 1.2

C8051F39x/37x 32.3.6. 16-Bit Pulse Width Modulator Mode A PCA module may also be operated in 16-Bit PWM mode. 16-bit PWM mode is independent of the other (8/9/10/11-bit) PWM modes. In this mode, the 16-bit capture/compare module defines the number of PCA clocks for the low time of the PWM signal. When the PCA counter matches the module contents, the out- put on CEXn is asserted high; when the 16-bit counter overflows, CEXn is asserted low. To output a vary- ing duty cycle, new value writes should be synchronized with PCA CCFn match interrupts. 16-Bit PWM Mode is enabled by setting the ECOMn, PWMn, and PWM16n bits in the PCA0CPMn register. For a vary- ing duty cycle, match interrupts should be enabled (ECCFn=1 AND MATn=1) to help synchronize the capture/compare register writes. If the MATn bit is set to 1, the CCFn flag for the module will be set each time a 16-bit comparator match (rising edge) occurs. The CF flag in PCA0CN can be used to detect the overflow (falling edge). The duty cycle for 16-Bit PWM Mode is given by Equation32.4. Important Note About Capture/Compare Registers: When writing a 16-bit value to the PCA0 Capture/ Compare registers, the low byte should always be written first. Writing to PCA0CPLn clears the ECOMn bit to 0; writing to PCA0CPHn sets ECOMn to 1. 65536–PCA0CPn Duty Cycle = ----------------------------------------------------- 65536 Equation 32.4. 16-Bit PWM Duty Cycle Using Equation32.4, the largest duty cycle is 100% (PCA0CPn=0), and the smallest duty cycle is 0.0015% (PCA0CPn=0xFFFF). A 0% duty cycle may be generated by clearing the ECOMn bit to 0. Write to PCA0CPLn 0 Reset ENB Write to PCA0CPHn ENB 1 PCA0CPMn PECCMTPE WCAAAOWC PCA0CPHn PCA0CPLn MOPPTGMC 1MPNnnnF 6nnn n n 1 00x0 x Enable 16-bit Comparator match S SET Q CEXn Crossbar Port I/O RCLR Q PCA Timebase PCA0H PCA0L Overflow Figure 32.10. PCA 16-Bit PWM Mode Rev. 1.2 285

C8051F39x/37x 32.4. Watchdog Timer Mode A programmable watchdog timer (WDT) function is available through the PCA Module 2. The WDT is used to generate a reset if the time between writes to the WDT update register (PCA0CPH2) exceed a specified limit. The WDT can be configured and enabled/disabled as needed by software. With the WDTE bit set in the PCA0MD register, Module 2 operates as a WDT. The Module 2 high byte is compared to the PCA counter high byte; the Module 2 low byte holds the offset to be used when WDT updates are performed. The watchdog timer is enabled on reset. Writes to some PCA registers are restricted while the watchdog timer is enabled. The WDT will generate a reset shortly after code begins execution. To avoid this reset, the WDT should be explicitly disabled (and optionally re-configured and re- enabled if it is used in the system). 32.4.1. Watchdog Timer Operation While the WDT is enabled:  PCA counter is forced on.  Writes to PCA0L and PCA0H are not allowed.  PCA clock source bits (CPS2–CPS0) are frozen.  PCA Idle control bit (CIDL) is frozen.  Module 2 is forced into software timer mode.  Writes to the Module 2 mode register (PCA0CPM2) are disabled. While the WDT is enabled, writes to the CR bit will not change the PCA counter state; the counter will run until the WDT is disabled. The PCA counter run control bit (CR) will read zero if the WDT is enabled but user software has not enabled the PCA counter. If a match occurs between PCA0CPH2 and PCA0H while the WDT is enabled, a reset will be generated. To prevent a WDT reset, the WDT may be updated with a write of any value to PCA0CPH2. Upon a PCA0CPH2 write, PCA0H plus the offset held in PCA0CPL2 is loaded into PCA0CPH2 (See Figure32.11). PCA0MD CWW CCCE PCA0CPH2 I DD PPPC DT L SSSF L EC 2 1 0 K 8-bit Match Reset Comparator Enable PCA0L Overflow PCA0CPL2 8-bit Adder PCA0H Adder Enable Write to PCA0CPH2 Figure 32.11. PCA Module 2 with Watchdog Timer Enabled 286 Rev. 1.2

C8051F39x/37x The 8-bit offset held in PCA0CPH2 is compared to the upper byte of the 16-bit PCA counter. This offset value is the number of PCA0L overflows before a reset. Up to 256 PCA clocks may pass before the first PCA0L overflow occurs, depending on the value of the PCA0L when the update is performed. The total off- set is then given (in PCA clocks) by Equation32.5, where PCA0L is the value of the PCA0L register at the time of the update. Offset = 256 PCA0CPL2+ 256–PCA0L Equation 32.5. Watchdog Timer Offset in PCA Clocks The WDT reset is generated when PCA0L overflows while there is a match between PCA0CPH2 and PCA0H. Software may force a WDT reset by writing a 1 to the CCF2 flag (PCA0CN.2) while the WDT is enabled. 32.4.2. Watchdog Timer Usage To configure the WDT, perform the following tasks: 1. Disable the WDT by writing a 0 to the WDTE bit. 2. Select the desired PCA clock source (with the CPS2–CPS0 bits). 3. Load PCA0CPL2 with the desired WDT update offset value. 4. Configure the PCA Idle mode (set CIDL if the WDT should be suspended while the CPU is in Idle mode). 5. Enable the WDT by setting the WDTE bit to 1. 6. Reset the WDT timer by writing to PCA0CPH2. The PCA clock source and Idle mode select cannot be changed while the WDT is enabled. The watchdog timer is enabled by setting the WDTE or WDLCK bits in the PCA0MD register. When WDLCK is set, the WDT cannot be disabled until the next system reset. If WDLCK is not set, the WDT is disabled by clearing the WDTE bit. The WDT is enabled following any reset. The PCA0 counter clock defaults to the system clock divided by 12, PCA0L defaults to 0x00, and PCA0CPL2 defaults to 0x00. Using Equation32.5, this results in a WDT timeout interval of 256 PCA clock cycles, or 3072 system clock cycles. Table32.3 lists some example tim- eout intervals for typical system clocks. Table 32.3. Watchdog Timer Timeout Intervals1 System Clock (Hz) PCA0CPL2 Timeout Interval (ms) 24,500,000 255 32.1 24,500,000 128 16.2 24,500,000 32 4.1 3,062,5002 255 257 3,062,5002 128 129.5 3,062,5002 32 33.1 32,000 255 24576 32,000 128 12384 32,000 32 3168 Notes: 1. Assumes SYSCLK/12 as the PCA clock source, and a PCA0L value of 0x00 at the update time. 2. Internal SYSCLK reset frequency=Internal Oscillator divided by 8. Rev. 1.2 287

C8051F39x/37x 32.5. Comparator Clear Function In 8/9/10/11/16-bit PWM modes, the comparator clear function utilizes the Comparator0 output synchro- nized to the system clock to clear CEXn to logic low for the current PWM cycle. This comparator clear func- tion can be enabled for each PWM channel by setting the CPCEn bits to 1 in the PCA0CLR SFR (see SFR Definition 32.4). When the comparator clear function is disabled, CEXn is unaffected. See Figure32.12. PCA0CLR PCA0CPMn CPCPOL CPCE2 CPCE1 CPCE0 PWM16n ECOMn CAPPn CAPNn MATn TOGn PWMn ECCFn Clear CEXn to logic low for current PWM cycle CP0 + 0 Comparator0 1 Input Mux CP0 - Figure 32.12. Comparator Clear Function Diagram The asynchronous Comparator0 output is logic high when the voltage of CP0+ is greater than CP0- and logic low when the voltage of CP0+ is less than CP0-. The polarity of the Comparator0 output is used to clear CEXn as follows: when CPCPOL=0, CEXn is forced to logic low on the falling edge of the Compar- ator0 output (see Figure32.13); when CPCPOL=0, CEXn is forced logic low on the rising edge of the Compartor0 output (see Figure32.14). CEXn (CPCEn = 0) Comparator0 Output (CPCPOL = 0) CEXn (CPCEn = 1) Figure 32.13. CEXn with CPCEn = 1, CPCPOL = 0 288 Rev. 1.2

C8051F39x/37x CEXn (CPCEn = 0) Comparator0 Output (CPCPOL = 1) CEXn (CPCEn = 1) Figure 32.14. CEXn with CPCEn = 1, CPCPOL = 1 In the PWM cycle following the current cycle, should the Comparator0 output remain logic low when CPCPOL=0 or logic high when CPCPOL=1, CEXn will continue to be logic low. See Figure32.15 and Figure32.16. CEXn (CPCEn = 0) Comparator0 Output (CPCPOL = 0) CEXn (CPCEn = 1) Figure 32.15. CEXn with CPCEn = 1, CPCPOL = 0 CEXn (CPCEn = 0) Comparator0 Output (CPCPOL = 1) CEXn (CPCEn = 1) Figure 32.16. CEXn with CPCEn = 1, CPCPOL = 1 Rev. 1.2 289

C8051F39x/37x 32.6. Register Descriptions for PCA0 Following are detailed descriptions of the special function registers related to the operation of the PCA. SFR Definition 32.1. PCA0CN: PCA Control Bit 7 6 5 4 3 2 1 0 Name CF CR CCF2 CCF1 CCF0 Type R/W R/W R R R R/W R/W R/W Reset 0 0 0 0 0 0 0 0 SFR Address=0xD8; SFR Page=All Pages; Bit-Addressable Bit Name Function 7 CF PCA Counter/Timer Overflow Flag. Set by hardware when the PCA Counter/Timer overflows from 0xFFFF to 0x0000. When the Counter/Timer Overflow (CF) interrupt is enabled, setting this bit causes the CPU to vector to the PCA interrupt service routine. This bit is not automatically cleared by hardware and must be cleared by software. 6 CR PCA Counter/Timer Run Control. This bit enables/disables the PCA Counter/Timer. 0: PCA Counter/Timer disabled. 1: PCA Counter/Timer enabled. 5:3 Unused Unused. Read=000b, Write=Don't care. 2 CCF2 PCA Module 2 Capture/Compare Flag. This bit is set by hardware when a match or capture occurs. When the CCF2 interrupt is enabled, setting this bit causes the CPU to vector to the PCA inter- rupt service routine. This bit is not automatically cleared by hardware and must be cleared by software. 1 CCF1 PCA Module 1 Capture/Compare Flag. This bit is set by hardware when a match or capture occurs. When the CCF1 interrupt is enabled, setting this bit causes the CPU to vector to the PCA inter- rupt service routine. This bit is not automatically cleared by hardware and must be cleared by software. 0 CCF0 PCA Module 0 Capture/Compare Flag. This bit is set by hardware when a match or capture occurs. When the CCF0 interrupt is enabled, setting this bit causes the CPU to vector to the PCA inter- rupt service routine. This bit is not automatically cleared by hardware and must be cleared by software. 290 Rev. 1.2

C8051F39x/37x SFR Definition 32.2. PCA0MD: PCA Mode Bit 7 6 5 4 3 2 1 0 Name CIDL WDTE WDLCK CPS2 CPS1 CPS0 ECF Type R/W R/W R/W R R/W R/W R/W R/W Reset 0 1 0 0 0 0 0 0 SFR Address=0xD9; SFR Page=All Pages Bit Name Function 7 CIDL PCA Counter/Timer Idle Control. Specifies PCA behavior when CPU is in Idle Mode. 0: PCA continues to function normally while the system controller is in Idle Mode. 1: PCA operation is suspended while the system controller is in Idle Mode. 6 WDTE Watchdog Timer Enable. If this bit is set, PCA Module 2 is used as the watchdog timer. 0: Watchdog Timer disabled. 1: PCA Module 2 enabled as Watchdog Timer. 5 WDLCK Watchdog Timer Lock. This bit locks/unlocks the Watchdog Timer Enable. When WDLCK is set, the Watchdog Timer may not be disabled until the next system reset. 0: Watchdog Timer Enable unlocked. 1: Watchdog Timer Enable locked. 4 Unused Unused. Read=0b, Write=Don't care. 3:1 CPS[2:0] PCA Counter/Timer Pulse Select. These bits select the timebase source for the PCA counter 000: System clock divided by 12 001: System clock divided by 4 010: Timer 0 overflow 011: High-to-low transitions on ECI (max rate=system clock divided by 4) 100: System clock 101: External clock divided by 8 (synchronized with the system clock) 110: Low frequency oscillator divided by 8 111: Reserved 0 ECF PCA Counter/Timer Overflow Interrupt Enable. This bit sets the masking of the PCA Counter/Timer Overflow (CF) interrupt. 0: Disable the CF interrupt. 1: Enable a PCA Counter/Timer Overflow interrupt request when CF (PCA0CN.7) is set. Note: When the WDTE bit is set to 1, the other bits in the PCA0MD register cannot be modified. To change the contents of the PCA0MD register, the Watchdog Timer must first be disabled. Rev. 1.2 291

C8051F39x/37x SFR Definition 32.3. PCA0PWM: PCA PWM Configuration Bit 7 6 5 4 3 2 1 0 Name ARSEL ECOV COVF CLSEL[1:0] Type R/W R/W R/W R R R R/W Reset 0 0 0 0 0 0 0 0 SFR Address=0xF7; SFR Page=All Pages Bit Name Function 7 ARSEL Auto-Reload Register Select. This bit selects whether to read and write the normal PCA capture/com- pare registers (PCA0CPn), or the Auto-Reload registers at the same SFR addresses. This function is used to define the reload value for 9, 10, and 11-bit PWM modes. In all other modes, the Auto-Reload regis- ters have no function. 0: Read/Write Capture/Compare Registers at PCA0CPHn and PCA0CPLn. 1: Read/Write Auto-Reload Registers at PCA0CPHn and PCA0CPLn. 6 ECOV Cycle Overflow Interrupt Enable. This bit sets the masking of the Cycle Overflow Flag (COVF) interrupt. 0: COVF will not generate PCA interrupts. 1: A PCA interrupt will be generated when COVF is set. 5 COVF Cycle Overflow Flag. This bit indicates an overflow of the 8th, 9th, 10th, or 11th bit of the main PCA counter (PCA0). The specific bit used for this flag depends on the setting of the Cycle Length Select bits. The bit can be set by hardware or software, but must be cleared by software. 0: No overflow has occurred since the last time this bit was cleared. 1: An overflow has occurred since the last time this bit was cleared. 4:2 Unused Unused. Read=000b; Write=Don’t care. 1:0 CLSEL[1:0] Cycle Length Select. When 16-bit PWM mode is not selected, these bits select the length of the PWM cycle, between 8, 9, 10, or 11 bits. This affects all channels configured for PWM which are not using 16-bit PWM mode. These bits are ignored for individual channels configured to16-bit PWM mode. 00: 8 bits. 01: 9 bits. 10: 10 bits. 11: 11 bits. 292 Rev. 1.2

C8051F39x/37x SFR Definition 32.4. PCA0CLR: PCA Comparator Clear Control Bit 7 6 5 4 3 2 1 0 Name CPCPOL CPCE2 CPCE1 CPCE0 Type R/W R/W R/W R/W R/W R/W R/W R/W Reset 0 0 0 0 0 0 0 0 SFR Address=0xCE; SFR Page=All Pages Bit Name Function 7 CPCPOL Comparator Clear Polarity. Selects the polarity of the comparator result that will clear the PCA channel(s). 0: PCA channel(s) will be cleared when comparator result goes logic low 1: PCA channel(s) will be cleared when comparator result goes logic high 6:3 Reserved Must write 0000b. 2 CPCE2 Comparator Clear Enable for CEX2. Enables the comparator clear function on PCA channel 2. 1 CPCE1 Comparator Clear Enable for CEX1. Enables the comparator clear function on PCA channel 1. 0 CPCE0 Comparator Clear Enable for CEX0. Enables the comparator clear function on PCA channel 0. Rev. 1.2 293

C8051F39x/37x SFR Definition 32.5. PCA0CPMn: PCA Capture/Compare Mode Bit 7 6 5 4 3 2 1 0 Name PWM16n ECOMn CAPPn CAPNn MATn TOGn PWMn ECCFn Type R/W R/W R/W R/W R/W R/W R/W R/W Reset 0 0 0 0 0 0 0 0 SFR Addresses: PCA0CPM0=0xDA, PCA0CPM1=0xDB, PCA0CPM2=0xDC SFR Pages: PCA0CPM0=All Pages, PCA0CPM1=All Pages, PCA0CPM2=All Pages Bit Name Function 7 PWM16n 16-bit Pulse Width Modulation Enable. This bit enables 16-bit mode when Pulse Width Modulation mode is enabled. 0: 8 to 11-bit PWM selected. 1: 16-bit PWM selected. 6 ECOMn Comparator Function Enable. This bit enables the comparator function for PCA module n when set to 1. 5 CAPPn Capture Positive Function Enable. This bit enables the positive edge capture for PCA module n when set to 1. 4 CAPNn Capture Negative Function Enable. This bit enables the negative edge capture for PCA module n when set to 1. 3 MATn Match Function Enable. This bit enables the match function for PCA module n when set to 1. When enabled, matches of the PCA counter with a module's capture/compare register cause the CCFn bit in PCA0MD register to be set to logic 1. 2 TOGn Toggle Function Enable. This bit enables the toggle function for PCA module n when set to 1. When enabled, matches of the PCA counter with a module's capture/compare register cause the logic level on the CEXn pin to toggle. If the PWMn bit is also set to logic 1, the mod- ule operates in Frequency Output Mode. 1 PWMn Pulse Width Modulation Mode Enable. This bit enables the PWM function for PCA module n when set to 1. When enabled, a pulse width modulated signal is output on the CEXn pin. 8 to 11-bit PWM is used if PWM16n is cleared; 16-bit mode is used if PWM16n is set to logic 1. If the TOGn bit is also set, the module operates in Frequency Output Mode. 0 ECCFn Capture/Compare Flag Interrupt Enable. This bit sets the masking of the Capture/Compare Flag (CCFn) interrupt. 0: Disable CCFn interrupts. 1: Enable a Capture/Compare Flag interrupt request when CCFn is set. Note: When the WDTE bit is set to 1, the PCA0CPM2 register cannot be modified, and module 2 acts as the watchdog timer. To change the contents of the PCA0CPM2 register or the function of module 2, the Watchdog Timer must be disabled. 294 Rev. 1.2

C8051F39x/37x SFR Definition 32.6. PCA0L: PCA Counter/Timer Low Byte Bit 7 6 5 4 3 2 1 0 Name PCA0[7:0] Type R/W R/W R/W R/W R/W R/W R/W R/W Reset 0 0 0 0 0 0 0 0 SFR Address=0xF9; SFR Page=All Pages Bit Name Function 7:0 PCA0[7:0] PCA Counter/Timer Low Byte. The PCA0L register holds the low byte (LSB) of the 16-bit PCA Counter/ Timer. Note: When the WDTE bit is set to 1, the PCA0L register cannot be modified by software. To change the contents of the PCA0L register, the Watchdog Timer must first be disabled. SFR Definition 32.7. PCA0H: PCA Counter/Timer High Byte Bit 7 6 5 4 3 2 1 0 Name PCA0[15:8] Type R/W R/W R/W R/W R/W R/W R/W R/W Reset 0 0 0 0 0 0 0 0 SFR Address=0xFA; SFR Page=All Pages Bit Name Function 7:0 PCA0[15:8] PCA Counter/Timer High Byte. The PCA0H register holds the high byte (MSB) of the 16-bit PCA Counter/Timer. Reads of this register will read the contents of a “snapshot” register, whose contents are updated only when the con- tents of PCA0L are read (see Section 32.1). Note: When the WDTE bit is set to 1, the PCA0H register cannot be modified by software. To change the contents of the PCA0H register, the Watchdog Timer must first be disabled. Rev. 1.2 295

C8051F39x/37x SFR Definition 32.8. PCA0CPLn: PCA Capture Module Low Byte Bit 7 6 5 4 3 2 1 0 Name PCA0CPn[7:0] Type R/W R/W R/W R/W R/W R/W R/W R/W Reset 0 0 0 0 0 0 0 0 SFR Addresses: PCA0CPL0=0xFB, PCA0CPL1=0xE9, PCA0CPL2=0xEB SFR Pages: PCA0CPL0=All Pages, PCA0CPL1=All Pages, PCA0CPL2=All Pages Bit Name Function 7:0 PCA0CPn[7:0] PCA Capture Module Low Byte. The PCA0CPLn register holds the low byte (LSB) of the 16-bit capture module n. This register address also allows access to the low byte of the corresponding PCA channel’s auto-reload value for 9, 10, or 11- bit PWM mode. The ARSEL bit in register PCA0PWM controls which register is accessed. Note: A write to this register will clear the module’s ECOMn bit to a 0. SFR Definition 32.9. PCA0CPHn: PCA Capture Module High Byte Bit 7 6 5 4 3 2 1 0 Name PCA0CPn[15:8] Type R/W R/W R/W R/W R/W R/W R/W R/W Reset 0 0 0 0 0 0 0 0 SFR Addresses: PCA0CPH0=0xFC, PCA0CPH1=0xEA, PCA0CPH2=0xEC SFR Pages: PCA0CPH0=All Pages, PCA0CPH1=All Pages, PCA0CPH2=All Pages Bit Name Function 7:0 PCA0CPn[15:8] PCA Capture Module High Byte. The PCA0CPHn register holds the high byte (MSB) of the 16-bit cap- ture module n. This register address also allows access to the high byte of the corre- sponding PCA channel’s auto-reload value for 9, 10, or 11-bit PWM mode. The ARSEL bit in register PCA0PWM controls which register is accessed. Note: A write to this register will set the module’s ECOMn bit to a 1. 296 Rev. 1.2

C8051F39x/37x 33. C2 Interface C8051F39x/37x devices include an on-chip Silicon Labs 2-Wire (C2) debug interface to allow Flash pro- gramming and in-system debugging with the production part installed in the end application. The C2 inter- face uses a clock signal (C2CK) and a bi-directional C2 data signal (C2D) to transfer information between the device and a host system. See the C2 Interface Specification for details on the C2 protocol. 33.1. C2 Interface Registers The following describes the C2 registers necessary to perform Flash programming through the C2 inter- face. All C2 registers are accessed through the C2 interface as described in the C2 Interface Specification. C2 Register Definition 33.1. C2ADD: C2 Address Bit 7 6 5 4 3 2 1 0 Name C2ADD[7:0] Type R/W Reset 0 0 0 0 0 0 0 0 Bit Name Function 7:0 C2ADD[7:0] C2 Address. The C2ADD register is accessed via the C2 interface to select the target Data register for C2 Data Read and Data Write commands. Address Description 0x00 Selects the Device ID register for Data Read instructions 0x01 Selects the Revision ID register for Data Read instructions 0x02 Selects the C2 Flash Programming Control register for Data Read/Write instructions 0xB4 Selects the C2 Flash Programming Data register for Data Read/ Write instructions Rev. 1.2 297

C8051F39x/37x C2 Register Definition 33.2. DEVICEID: C2 Device ID Bit 7 6 5 4 3 2 1 0 Name DEVICEID[7:0] Type R/W Reset 0 0 1 0 1 0 1 1 C2 Address: 0x00 Bit Name Function 7:0 DEVICEID[7:0] Device ID. This read-only register returns the 8-bit device ID: 0x2B (C8051F39x/37x). C2 Register Definition 33.3. REVID: C2 Revision ID Bit 7 6 5 4 3 2 1 0 Name REVID[7:0] Type R/W Reset Varies Varies Varies Varies Varies Varies Varies Varies C2 Address: 0x01 Bit Name Function 7:0 REVID[7:0] Revision ID. This read-only register returns the 8-bit revision ID. For example: 0x00=Revision A. 298 Rev. 1.2

C8051F39x/37x C2 Register Definition 33.4. FPCTL: C2 Flash Programming Control Bit 7 6 5 4 3 2 1 0 Name FPCTL[7:0] Type R/W Reset 0 0 0 0 0 0 0 0 C2 Address: 0x02 Bit Name Function 7:0 FPCTL[7:0] Flash Programming Control Register. This register is used to enable Flash programming via the C2 interface. To enable C2 Flash programming, the following codes must be written in order: 0x02, 0x01. Note that once C2 Flash programming is enabled, a system reset must be issued to resume normal operation. C2 Register Definition 33.5. FPDAT: C2 Flash Programming Data Bit 7 6 5 4 3 2 1 0 Name FPDAT[7:0] Type R/W Reset 0 0 0 0 0 0 0 0 C2 Address: 0xB4 Bit Name Function 7:0 FPDAT[7:0] C2 Flash Programming Data Register. This register is used to pass Flash commands, addresses, and data during C2 Flash accesses. Valid commands are listed below. Code Command 0x06 Flash Block Read 0x07 Flash Block Write 0x08 Flash Page Erase 0x03 Device Erase Rev. 1.2 299

C8051F39x/37x 33.2. C2 Pin Sharing The C2 protocol allows the C2 pins to be shared with user functions so that in-system debugging and Flash programming may be performed. This is possible because C2 communication is typically performed when the device is in the halt state, where all on-chip peripherals and user software are stalled. In this halted state, the C2 interface can safely ‘borrow’ the C2CK (RST) and C2D pins. In most applications, external resistors are required to isolate C2 interface traffic from the user application. A typical isolation configuration is shown in Figure33.1. C8051Fxxx /Reset (a) C2CK Input (b) C2D Output (c) C2 Interface Master Figure 33.1. Typical C2 Pin Sharing The configuration in Figure33.1 assumes the following: 1. The user input (b) cannot change state while the target device is halted. 2. The RST pin on the target device is used as an input only. Additional resistors may be necessary depending on the specific application. 300 Rev. 1.2

DOCUMENT CHANGE LIST Table7.6 on page37.  Updated typical INL and DNL in Table7.10 on Revision 0.1 to Revision 0.7 page39.  Added Section 8.1 “Temperature in Two’s  Updated resolution in Table7.12 on page40. Complement”  Updated typical and maximum INL and DNL in  Changed clock cycles for “CJNE A, direct, re” to “4/ Table7.15 on page42. 6” in Section 15. “CIP-15 Microcontroller”  Updated typical full scale error in Table7.15 on  Changed bit 5 of CRC0CNT to reserved in Section page42. 23.“Cyclic Redundancy Check Unit” (CRC0)  Updated references to Table28.3 in the SMB0CN  Changed SFRPGCN reset value to “0x01” in Section and SMB1CN SFR definitions. 19.“Special Function Registers” Revision 0.71 to Revision 1.0  Added Section 19.2 “Interrupts and Automatic SFR Paging”  Added typical precision temperature sensor curve  Added Section 19.3 “SFR Page Stack Example” Figure7.3on page46.  Corrected incorrect references to C8501F34x in  Added note to CLKSEL SFR definition. Section 2. “Ordering Information”  Corrected CPCPOL description in the PCA0CLR  Removed “The C8051F37x does not include the 4x SFR definition. clock multiplier” bullet point from Section 3.1  Updated C mode K factors in the OSCXCN SFR  Removed “External Oscillator C and RC Modes” definition. bullet point from Section 3.1  Updated maximum normal mode IDD (F =50MHz,  Updated the block diagram on the front page to F=25MHz) in Table7.2 on page33. show EEPROM and 500 ksps ADC  Updated typical suspend and stop mode digital  Removed references to the REG0MD bit and low supply current in Table7.2 on page33. power mode in Section 13.1  Updated typical precision temperature sensor  Removed REG0MD bit in the REG0CN SFR absolute error in Table7.12 on page40. definition. This bit (bit 2) is now reserved.  Updated maximum precision temperature sensor  Section 22. “EEPROM” completely rewritten INL in Table7.12 on page40.  Moved the “from IPH, EIPH1 or EIPH2” text from the  Updated minimum IDAC DNL in Table7.15 on LSB column to the MSB column in Table 20.1 page42.  Moved the “from IP, EIP1 or EIP2” text from the MSB  Updated minimum and maximum IDAC full scale column to the LSB column in Table 20.1 error in Table7.15 on page42.  Changed Figure 27.4 to show all five footnotes  Updated typical IDAC gain variation in Table7.15 on page42.  Changed Figure 27.5 to show correct SF signals and all five footnotes  Updated maximum comparator supply current at DC in Table7.16 on page43.  Added 5V tolerance and lock byte address bullet points to Section 3.1. “Hardware Incompatibilities”  Corrected flash security restrictions for erase page containing lock byte (if no pages are locked) in Revision 0.7 to Revision 0.71 Table21.1 on page133.  Updated part numbers in Table2.1 on page20. Revision 0.71 to Revision 1.0  Updated replacement part numbers in Table3.1 on  Corrected EESCL and EESDA pin assignments to page21 to match Flash sizes. P2.2 and P2.3 respectively in Figure27.3 and  Corrected units for normal and active mode IDD Figure27.4. (V = 3.0V, F = 80kHz) in Table7.2 on page33. DD  Corrected bit 5 of CRC0CNT to CRC0CNT[5] in  Updated maximum normal mode IDD in Table7.2 on Section 23. “Cyclic Redundancy Check Unit” page33. (CRC0).  Added EESDA and EESCL DC electrical  Corrected C8051F374/5 flash size to 8kB in characteristics to Table7.3 on page35. Figure17.1 and Figure17.2.  Added EEPROM supply current to Table7.6 on  Correct C8051F394/5 flash size to 8kB in page37. Figure17.2  Added maximum EESCL clock frequency to Rev. 1.2 301

Revision 1.0 to Revision 1.1  Corrected the CRC0CNT size to [5:0] and removed the second note on the CRC0CNT field in the CRC0CNT register (SFR Definition 23.5). The issue where only 31 blocks can be calculated at a time does not apply to this device family.  Swapped the EESCL (correct pin is P2.2) and EESDA (correct pin is P2.3) in Figure “27.3Crossbar Priority Decoder - Possible Pin Assignments” on page178 and Figure “27.4Crossbar Priority Decoder Example” on page179.  Updated Figure “17.1C8051F39x/37x Memory Map” on page93 and Figure “17.2Flash Program Memory Map” on page94 to correctly list C8051F374/5 with 8 kB of flash.  Removed the sentence regarding maximum VDD ramp time from “Power-On Reset” on page156.  Updated Figure “24.2Power-On and VDD Monitor Reset Timing” on page156 to use the V RST_LOW threshold for power-on, since this is the default setting.  Removed the part numbers and added a “16-byte page” condition on the EEPROM write time in Table7.6, “EEPROM Electrical Characteristics,” on page37.  Clarified throughout “EEPROM (C8051F37x)” on page140 that writes are 16-byte page aligned.  Updated the maximum VREF Short-Circuit Current specification in Table7.13, “Voltage Reference Electrical Characteristics,” on page41. Revision 1.1 to Revision 1.2  Updated Table2.1, “Product Selection Guide,” on page20 to show that the C8051F37x devices are not recommended for new designs.  Added recommended settings for PFEN and FLRT for SYSCLK greater than 25 MHz in Section “16.Prefetch Engine” on page92.  Corrected reset value of the PFE0CN register in SFR Definition 16.1.  Added footnote to Table28.3, “Sources for Hardware Changes to SMBnCN,” on page204. 302 Rev. 1.2

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