Mixed-Signal Byte-Programmable EPROM MCU
C8051T600/1/2/3/4/5/6
Rev. 1.2 3/09 Copyright © 2009 by Silicon Laboratorie s C8051T600/1/2/3/4/5/6
This information applies to a product under development. Its characteristics and specifications are subject to change without notice.
Analog Peripherals
-10-Bit ADC (‘T600/602/604 only)
•Up to 500 ksps
•Up to 8 external inputs
•VREF external pin, Internal Regulator or V DD
•Internal or external start of conversion source
•Built-in temperature sensor
-Comparator
•Programmable hysteresis and response time
•Configurable as interrupt or reset source
•Low current
On-Chip Debug
-C8051F300 can be used as code developme nt
platform; complete development kit available
-On-chip debug circuitry facilitates full speed,
non-intrusive in-system debug
-Provides breakpoints, single stepping,
inspect/modify memory and registers
Supply Voltage 1.8 to 3.6 V
-On-chip LDO for internal core supply
-Built-in voltage supply monitor
Temperatu re Ra ng e : –4 0 to +85 °C
Package Options:
-3 x 3 mm QFN11
-2 x 2 mm QFN10 (C8051T606 Only)
-MSOP10 (C8051T606 Only)
-SOIC14 (C8051T600/1/2/3/4/5 Only)
High-S peed 8051 µC Core
-Pipelined instruction architecture; executes 70% of
instructions in 1 or 2 system clocks
-Up to 25 MIPS throughput with 25 MHz clock
-Expanded interrupt handler
Memory
-256 or 128 Bytes internal data RAM
-8, 4, 2, or 1.5 kB byte-programmable EPROM code
memory
Digital Peripherals
-Up to 8 Port I/O with high sink current capability
-Hardware enhanced UART and SMBus™ serial
ports
-Three general purpose 16-bit counter/timers
-16-bit programmable counter array (PCA) with three
capture/compare modules
•8 or 16-bit PWM
•Rising / falling edge capture
•Frequency output
•Software timer
Clock Sources
-Internal oscillator: 24.5 MHz with ±2% accuracy
supports crystal-less UART operation
-External oscillator: RC, C, or CMOS Clock
-Can switch between clock sources on-the-fly; useful
in power saving modes
ANALOG
PERIPHERALS
1.5/2/4/8kB
EPROM 128/256 B
SRAM
POR
DEBUG
CIRCUITRY
12
INTERRUPTS
8051 CPU
(25MIPS)
DIGITAL I/O
CALIBRATED PRECISION INTERNAL
OSCILLATOR
HIGH-SPEED CONTROLLER CORE
I/O Port
CROSSBAR
UART
SMBus
PCA
Timer 0
Timer 1
Timer 2VOLTAGE
COMPARATOR
+
-
WDT
10-bit
500ksps
ADC
TEMP
SENSOR
A
M
U
X
C8051T600/2/4
C8051T600/1/2/3/4/5/6
2 Rev. 1.2
Table of Contents
1. System Overview..................................................................................................... 13
2. Ordering Information............................................................................................... 16
3. Pin Definitions.......................................................................................................... 17
4. QFN-11 Package Specifications............................................................................. 22
5. SOIC-14 Package Specifications............................................................................ 24
6. MSOP-10 Package Specifications.......................................................................... 26
7. QFN-10 Package Specifications............................................................................. 28
8. Electrical Characteristics........................................................................................ 30
8.1. Absolute Maximum Specifications..................................................................... 30
8.2. Electrical Characteristics................................................................................... 31
8.3. Typical Performance Curves............................................................................. 38
9. 10-Bit ADC (ADC0, C8051T600/2/4 only)................................................................ 40
9.1. Output Code Formatting.................................................................................... 41
9.2. 8-Bit Mode......................................................................................................... 41
9.3. Modes of Operation........................................................................................... 41
9.3.1. Starting a Conversion................................................................................ 41
9.3.2. Tracking Modes......................................................................................... 42
9.3.3. Settling Time Requirements...................................................................... 43
9.4. Programmable Window Detector....................................................................... 47
9.4.1. Window Detector Example........................................................................ 49
9.5. ADC0 Analog Multiplexer (C8051T600/2/4 only)............................................... 50
10. Temperature Sensor (C8051T600/2/4 only) ......................................................... 52
10.1. Calibration ....................................................................................................... 52
11. Voltage Reference Options................................................................................... 55
12. Voltage Regulator (REG0)..................................................................................... 57
13. Comparator0........................................................................................................... 59
13.1. Comparator Multiplexer................................................................................... 63
14. CIP-51 Microcontroller........................................................................................... 65
14.1. Instruction Set.................................................................................................. 66
14.1.1. Instruction and CPU Timing.................................................................... 66
14.2. CIP-51 Register Descriptions.......................................................................... 71
15. Memory Organization............................................................................................ 74
15.1. Program Memory............................................................................................. 74
15.2. Data Memory................................................................................................... 75
15.2.1. Internal RAM........................................................................................... 75
15.2.1.1. General Purpose Registers ............................................................ 76
15.2.1.2. Bit Addressable Locations.............................................................. 76
15.2.1.3. Stack ............................................................................................ 76
16. Special Function Registers................................................................................... 77
17. Interrupts................................................................................................................ 80
17.1. MCU Interrupt Sources and Vectors................................................................ 81
17.1.1. Interrupt Priorities.................................................................................... 81
17.1.2. Interrupt Latency..................................................................................... 81
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C8051T600/1/2/3/4/5/6
17.2. Interrupt Register Descriptions........................................................................ 82
17.3. INT0 and INT1 External Interrupt Sources...................................................... 87
18. Power Management Modes................................................................................... 89
18.1. Idle Mode......................................................................................................... 89
18.2. Stop Mode....................................................................................................... 90
19. Reset Sources........................................................................................................ 92
19.1. Power-On Reset.............................................................................................. 93
19.2. Power-Fail Reset/VDD Monitor ....................................................................... 94
19.3. External Reset................................................................................................. 94
19.4. Missing Clock Detector Reset ......................................................................... 94
19.5. Comparator0 Reset......................................................................................... 94
19.6. PCA Watchdog Timer Reset ........................................................................... 94
19.7. EPROM Error Reset........................................................................................ 95
19.8. Software Reset................................................................................................ 95
20. EPROM Memory..................................................................................................... 97
20.1. Programming and Reading the EPROM Memory ........................................... 97
20.1.1. EPROM Write Procedure........................................................................ 97
20.1.2. EPROM Read Procedure........................................................................ 98
20.2. Security Options.............................................................................................. 98
20.3. Program Memory CRC.................................................................................... 99
20.3.1. Performing 32-bit CRCs on Full EPROM Content .................................. 99
20.3.2. Performing 16-bit CRCs on 256-Byte EPROM Blocks............................ 99
21. Oscillators and Clock Selection......................................................................... 100
21.1. System Clock Selection................................................................................. 100
21.2. Programmable Internal High-Frequency (H-F) Oscillator.............................. 101
21.3. External Oscillator Drive Circuit. .................................................................... 103
21.3.1. External RC Example............................................................................ 105
21.3.2. External Capacitor Example.................................................................. 105
22. Port Input/Output................................................................................................. 106
22.1. Port I/O Modes of Operation.......................................................................... 107
22.1.1. Port Pins Configured for Analog I/O...................................................... 107
22.1.2. Port Pins Configured For Digital I/O...................................................... 107
22.1.3. Interfacing Port I/O to 5V Logic............................................................. 108
22.2. Assigning Port I/O Pins to Analog and Digital Functions............................... 109
22.2.1. Assigning Port I/O Pins to Analog Functions ........................................ 109
22.2.2. Assigning Port I/O Pins to Digital Functions.......................................... 109
22.2.3. Assigning Port I/O Pins to External Digital Event Capture Functions ... 110
22.3. Priority Crossbar Decoder............................................................................. 111
22.4. Port I/O Initialization ...................................................................................... 114
22.5. Special Function Registers for Accessing and Configuring Port I/O ............. 118
23. SMBus................................................................................................................... 120
23.1. Supporting Documents.................................................................................. 121
23.2. SMBus Configuration..................................................................................... 121
23.3. SMBus Operation.......................................................................................... 121
23.3.1. Transmitter Vs. Receiver....................................................................... 122
C8051T600/1/2/3/4/5/6
4 Rev. 1.2
23.3.2. Arbitration.............................................................................................. 122
23.3.3. Clock Low Extension............................................................................. 122
23.3.4. SCL Low Timeout.................................................................................. 122
23.3.5. SCL High (SMBus Free) Timeout ......................................................... 123
23.4. Using the SMBus........................................................................................... 123
23.4.1. SMBus Configuration Register.............................................................. 123
23.4.2. SMB0CN Control Register.................................................................... 127
23.4.3. Data Register........................................................................................ 130
23.5. SMBus Transfer Modes................................................................................. 131
23.5.1. Write Sequence (Master)...................................................................... 131
23.5.2. Read Sequence (Master)...................................................................... 132
23.5.3. Write Sequence (Slave)........................................................................ 133
23.5.4. Read Sequence (Slave)........................................................................ 134
23.6. SMBus Status Decoding................................................................................ 134
24. UART0................................................................................................................... 137
24.1. Enhanced Baud Rate Generation.................................................................. 138
24.2. Operational Modes........................................................................................ 139
24.2.1. 8-Bit UART............................................................................................ 139
24.2.2. 9-Bit UART............................................................................................ 140
24.3. Multiprocessor Communications ................................................................... 141
25. Timers................................................................................................................... 145
25.1. Timer 0 and Timer 1...................................................................................... 147
25.1.1. Mode 0: 13-bit Counter/Timer............................................................... 147
25.1.2. Mode 1: 16-bit Counter/Timer............................................................... 148
25.1.3. Mode 2: 8-bit Counter/Timer with Auto-Reload..................................... 149
25.1.4. Mode 3: Two 8-bit Counter/Timers (Timer 0 Only)... ............................. 150
25.2. Timer 2 .......................................................................................................... 155
25.2.1. 16-bit Timer with Auto-Reload............................................................... 155
25.2.2. 8-bit Timers with Auto-Reload............................................................... 156
26. Programmable Counter Array............................................................................. 160
26.1. PCA Counter/Timer....................................................................................... 161
26.2. PCA0 Interrupt Sources................................................................................. 162
26.3. Capture/Compare Modules ........................................................................... 163
26.3.1. Edge-triggered Capture Mode............................................................... 164
26.3.2. Software Timer (Compare) Mode.......................................................... 165
26.3.3. High-Speed Output Mode ..................................................................... 166
26.3.4. Frequency Output Mode ....................................................................... 167
26.3.5. 8-bit Pulse Width Modulator Mode....................................................... 168
26.3.6. 16-Bit Pulse Width Modulator Mode..................................................... 169
26.4. Watchdog Timer Mode.................................................................................. 170
26.4.1. Watchdog Timer Operation................................................................... 170
26.4.2. Watchdog Timer Usage ........................................................................ 171
26.5. Register Descriptions for PCA0..................................................................... 173
27. C2 Interface .......................................................................................................... 178
27.1. C2 Interface Registers................................................................................... 178
Rev. 1.2 5
C8051T600/1/2/3/4/5/6
27.2. C2 Pin Sharing .............................................................................................. 185
Document Change List.............................................................................................. 186
Contact Information................................................................................................... 188
C8051T600/1/2/3/4/5/6
6 Rev. 1.2
List of Figures
1. System Overview
Figure 1.1. C8051T600/2/4 Block Diagram ............................................................. 14
Figure 1.2. C8051T601/3/5 Block Diagram ............................................................. 14
Figure 1.3. C8051T606 Block Diagram ................................................................... 15
2. Ordering Information
3. Pin Definitions
Figure 3.1. C8051T600/1/2/3/4/5-GM QFN11 Pinout Diagram (Top View) ............. 19
Figure 3.2. C8051T600/1/2/3/4/5-GS SOIC14 Pinout Diagram (Top View) ............ 19
Figure 3.3. C8051T606-GM QFN11 Pinout Diagram (Top View) ............................ 20
Figure 3.4. C8051T606-GT MSOP10 Pinout Diagram (Top View) .......................... 20
Figure 3.5. C8051T606-ZM QFN10 Pinout Diagram (Top View) ............................ 21
4. QFN-11 Package Specifications
Figure 4.1. QFN-11 Package Drawing .................................................................... 22
Figure 4.2. QFN-11 PCB Land Pattern .................................................................... 23
5. SOIC-14 Package Specifications
Figure 5.1. SOIC-14 Package Drawing ................................................................... 24
Figure 5.2. SOIC-14 Recommended PCB Land Pattern ......................................... 25
6. MSOP-10 Package Specifications
Figure 6.1. MSOP-10 Package Drawing ................................................................. 26
Figure 6.2. MSOP-10 PCB Land Pattern ................................................................. 27
7. QFN-10 Package Specifications
Figure 7.1. QFN-10 Package Drawing .................................................................... 28
Figure 7.2. QFN-10 PCB Land Pattern .................................................................... 29
8. Electrical Characteristics
Figure 8.1. C8051T600/1/2/3/4/5 Normal Mode Supply Current vs. Frequency
(MPCE = 1) ........................................................................................................ 38
Figure 8.2. C8051T606 Normal Mode Supply Current vs. Frequency (MPCE = 1) 38
Figure 8.3. C8051T600/1/2/3/4/5 Idle Mode Supply Current vs. Frequency
(MPCE = 1) ........................................................................................................ 39
Figure 8.4. C8051T606 Idle Mode Digital Current vs. Frequency (MPCE = 1) ....... 39
9. 10-Bit ADC (ADC0, C8051T600/2/4 only)
Figure 9.1. ADC0 Functional Block Diagram ........................................................... 40
Figure 9.2. 10-Bit ADC Track and Conversion Example Timing ............................. 42
Figure 9.3. ADC0 Equivalent Input Circuits ............................................................. 43
Figure 9.4. ADC Window Compare Example: Right-Justified Data ......................... 49
Figure 9.5. ADC Window Compare Example: Left-Justified Data ........................... 49
Figure 9.6. ADC0 Multiplexer Block Diagram .......................................................... 50
10. Temperature Sensor (C8051T600/2/4 only)
Figure 10.1. Temperature Sensor Transfer Function .............................................. 52
Figure 10.2. Temperature Sensor Error with 1-Point Calibration at 0 °C ................ 53
11. Voltage Reference Options
Figure 11.1. Voltage Reference Functional Block Diagram ..................................... 55
12. Voltage Regulator (REG0)
Rev. 1.2 7
C8051T600/1/2/3/4/5/6
13. Comparator0
Figure 13.1. Comparator0 Functional Block Diagram ............................................. 59
Figure 13.2. Comparator Hysteresis Plot ................................................................ 60
Figure 13.3. Comparator Input Multiplexer Block Diagram ...................................... 63
14. CIP-51 Microcontroller
Figure 14.1. CIP-51 Block Diagram ......................................................................... 65
15. Memory Organization
Figure 15.1. Program Memory Map ......................................................................... 74
Figure 15.2. RAM Memory Map .............................................................................. 75
16. Special Function Registers
17. Interrupts
18. Power Management Modes
19. Reset Sources
Figure 19.1. Reset Sources ..................................................................................... 92
Figure 19.2. Power-On and VDD Monitor Reset Timing ......................................... 93
20. EPROM Memory
21. Oscillators and Clock Selection
Figure 21.1. Oscillator Options .............................................................................. 100
22. Port Input/Output
Figure 22.1. Port I/O Functional Block Diagram .................................................... 106
Figure 22.2. Port I/O Cell Block Diagram .............................................................. 107
Figure 22.3. Priority Crossbar Decoder Potential Pin Assignments ...................... 111
Figure 22.4. Priority Crossbar Decoder Example 1 - No Skipped Pins ................. 112
Figure 22.5. Priority Crossbar Decoder Example 2 - Skipping Pins ...................... 113
23. SMBus
Figure 23.1. SMBus Block Diagram ...................................................................... 120
Figure 23.2. Typical SMBus Configuration ............................................................ 121
Figure 23.3. SMBus Transaction ........................................................................... 122
Figure 23.4. Typical SMBus SCL Generation ........................................................ 124
Figure 23.5. Typical Master Write Sequence ........................................................ 131
Figure 23.6. Typical Master Read Sequence ........................................................ 132
Figure 23.7. Typical Slave Write Sequence .......................................................... 133
Figure 23.8. Typical Slave Read Sequence .......................................................... 134
24. UART0
Figure 24.1. UART0 Block Diagram ...................................................................... 137
Figure 24.2. UART0 Baud Rate Logic ................................................................... 138
Figure 24.3. UART Interconnect Diagram ............................................................. 139
Figure 24.4. 8-Bit UART Timing Diagram .............................................................. 139
Figure 24.5. 9-Bit UART Timing Diagram .............................................................. 140
Figure 24.6. UART Multi-Processor Mode Interconnect Diagram ......................... 141
25. Timers
Figure 25.1. T0 Mode 0 Block Diagram ................................................................. 148
Figure 25.2. T0 Mode 2 Block Diagram ................................................................. 149
Figure 25.3. T0 Mode 3 Block Diagram ................................................................. 150
Figure 25.4. Timer 2 16-Bit Mode Block Diagram ................................................. 155
C8051T600/1/2/3/4/5/6
8 Rev. 1.2
Figure 25.5. Timer 2 8-Bit Mode Block Diagram ................................................... 156
26. Programmable Counter Array
Figure 26.1. PCA Block Diagram ........................................................................... 160
Figure 26.2. PCA Counter/Timer Block Diagram ................................................... 161
Figure 26.3. PCA Interrupt Block Diagram ............................................................ 162
Figure 26.4. PCA Capture Mode Diagram ............................................................. 164
Figure 26.5. PCA Software Timer Mode Diagram ................................................. 165
Figure 26.6. PCA High-Speed Output Mode Diagram ........................................... 166
Figure 26.7. PCA Frequency Output Mode ........................................................... 167
Figure 26.8. PCA 8-Bit PWM Mode Diagram ........................................................ 168
Figure 26.9. PCA 16-Bit PWM Mode ..................................................................... 169
Figure 26.10. PCA Module 2 with Watchdog Timer Enabled ................................ 170
27. C2 Interface
Figure 27.1. Typical C2 Pin Sharing ...................................................................... 185
C8051T600/1/2/3/4/5/6
9 Rev. 1.2
List of Tables
1. System Overview
2. Ordering Information
Table 2.1. Product Selection Guide ......................................................................... 16
3. Pin Definitions
Table 3.1. Pin Definitions for the C8051T600/1/2/3/4/5 ........................................... 17
Table 3.2. Pin Definitions for the C8051T606 .......................................................... 18
4. QFN-11 Package Specifications
Table 4.1. QFN-11 Package Dimensions ................................................................ 22
Table 4.2. QFN-11 PCB Land Pattern Dimensions ................................................. 23
5. SOIC-14 Package Specifications
Table 5.1. SOIC-14 Package Dimensions ............................................................... 24
Table 5.2. SOIC-14 PCB Land Pattern Dimensions ................................................ 25
6. MSOP-10 Package Specifications
Table 6.1. MSOP-10 Package Dimensions ............................................................. 26
Table 6.2. MSOP-10 PCB Land Pattern Dimensions .............................................. 27
7. QFN-10 Package Specifications
Table 7.1. QFN-10 Package Dimensions ................................................................ 28
Table 7.2. QFN-10 PCB Land Pattern Dimensions ................................................. 29
8. Electrical Characteristics
Table 8.1. Absolute Maximum Ratings .................................................................... 30
Table 8.2. Global Electrical Characteristics ............................................................. 31
Table 8.3. Port I/O DC Electrical Characteristics ..................................................... 33
Table 8.4. Reset Electrical Characteristics .............................................................. 34
Table 8.5. Internal Voltage Regulator Electrical Characteristics ............................. 34
Table 8.6. EPROM Electrical Characteristics .......................................................... 34
Table 8.7. Internal High-Frequency Oscillator Electrical Characteristics ................. 35
Table 8.8. Temperature Sensor Electrical Characteristics ...................................... 35
Table 8.9. Voltage Reference Electrical Characteristics ......................................... 35
Table 8.10. ADC0 Electrical Characteristics ............................................................ 36
Table 8.11. Comparator Electrical Characteristics .................................................. 37
9. 10-Bit ADC (ADC0, C8051T600/2/4 only)
10. Temperature Sensor (C8051T600/2/4 only)
11. Voltage Reference Options
12. Voltage Regulator (REG0)
13. Comparator0
14. CIP-51 Microcontroller
Table 14.1. CIP-51 Instruction Set Summary .......................................................... 67
15. Memory Organization
16. Special Function Registers
Table 16.1. Special Function Register (SFR) Memory Map .................................... 77
Table 16.2. Special Function Registers ................................................................... 77
17. Interrupts
Table 17.1. Interrupt Summary ................................................................................ 82
Rev. 1.2 10
C8051T600/1/2/3/4/5/6
18. Power Management Modes
19. Reset Sources
20. EPROM Memory
Table 20.1. Security Byte Decoding ........................................................................ 98
21. Oscillators and Clock Selection
22. Port Input/Output
Table 22.1. Port I/O Assignment for Analog Functions ......................................... 109
Table 22.2. Port I/O Assignment for Digital Functions ........................................... 109
Table 22.3. Port I/O Assignment for External Digital Event Capture Functions .... 110
23. SMBus
Table 23.1. SMBus Clock Source Selection .......................................................... 124
Table 23.2. Minimum SDA Setup and Hold Times ................................................ 125
Table 23.3. Sources for Hardware Changes to SMB0CN ..................................... 129
Table 23.4. SMBus Status Decoding ..................................................................... 135
24. UART0
Table 24.1. Timer Settings for Standard Baud Rates
Using The Internal 24.5 MHz Oscillator .............................................. 144
Table 24.2. Timer Settings for Standard Baud Rates
Using an External 22.1184 MHz Oscillator ......................................... 144
25. Timers
26. Programmable Counter Array
Table 26.1. PCA Timebase Input Options ............................................................. 161
Table 26.2. PCA0CPM Bit Settings for PCA Capture/Compare Modules ............. 163
Table 26.3. Watchdog Timer Timeout Intervals1 ................................................... 172
27. C2 Interface
C8051T600/1/2/3/4/5/6
11 Rev. 1.2
List of Registers
SFR Definition 9.1. ADC0CF: ADC0 Configuration ...................................................... 44
SFR Definition 9.2. ADC0H: ADC0 Data Word MSB .................................................... 45
SFR Definition 9.3. ADC0L: ADC0 Data Word LSB ...................................................... 45
SFR Definition 9.4. ADC0CN: ADC0 Control ................................................................ 46
SFR Definition 9.5. ADC0GTH: ADC0 Greater-Than Data High Byte .......................... 47
SFR Definition 9.6. ADC0GTL: ADC0 Greater-Than Data Low Byte ............................ 47
SFR Definition 9.7. ADC0LTH: ADC0 Less-Than Data High Byte ................................ 48
SFR Definition 9.8. ADC0LTL: ADC0 Less-Than Data Low Byte ................................. 48
SFR Definition 9.9. AMX0SL: AMUX0 Positive Channel Select ................................... 51
SFR Definition 10.1. TOFFH: Temperature Offset Measurement High Byte ................ 54
SFR Definition 10.2. TOFFL: Temperature Offset Measurement Low Byte ................. 54
SFR Definition 11.1. REF0CN: Reference Control ....................................................... 56
SFR Definition 12.1. REG0CN: Voltage Regulator Control .......................................... 58
SFR Definition 13.1. CPT0CN: Comparator0 Control ................................................... 61
SFR Definition 13.2. CPT0MD: Comparator0 Mode Selection ..................................... 62
SFR Definition 13.3. CPT0MX: Comparator0 MUX Selection ...................................... 64
SFR Definition 14.1. DPL: Data Pointer Low Byte ........................................................ 71
SFR Definition 14.2. DPH: Data Pointer High Byte ....................................................... 71
SFR Definition 14.3. SP: Stack Pointer ......................................................................... 72
SFR Definition 14.4. ACC: Accumulator ....................................................................... 72
SFR Definition 14.5. B: B Register ................................................................................ 72
SFR Definition 14.6. PSW: Program Status Word ........................................................ 73
SFR Definition 17.1. IE: Interrupt Enable ...................................................................... 83
SFR Definition 17.2. IP: Interrupt Priority ...................................................................... 84
SFR Definition 17.3. EIE1: Extended Interrupt Enable 1 .............................................. 85
SFR Definition 17.4. EIP1: Extended Interrupt Priority 1 .............................................. 86
SFR Definition 17.5. IT01CF: INT0/INT1 Configuration ................................................ 88
SFR Definition 18.1. PCON: Power Control .................................................................. 91
SFR Definition 19.1. RSTSRC: Reset Source .............................................................. 96
SFR Definition 21.1. OSCICL: Internal H-F Oscillator Calibration .............................. 101
SFR Definition 21.2. OSCICN: Internal H-F Oscillator Control ................................... 102
SFR Definition 21.3. OSCXCN: External Oscillator Control ........................................ 104
SFR Definition 22.1. XBR0: Port I/O Crossbar Register 0 .......................................... 115
SFR Definition 22.2. XBR1: Port I/O Crossbar Register 1 .......................................... 116
SFR Definition 22.3. XBR2: Port I/O Crossbar Register 2 .......................................... 117
SFR Definition 22.4. P0: Port 0 ................................................................................... 118
SFR Definition 22.5. P0MDIN: Port 0 Input Mode ....................................................... 119
SFR Definition 22.6. P0MDOUT: Port 0 Output Mode ................................................ 119
SFR Definition 23.1. SMB0CF: SMBus Clock/Configuration ...................................... 126
SFR Definition 23.2. SMB0CN: SMBus Control .......................................................... 128
SFR Definition 23.3. SMB0DAT: SMBus Data ............................................................ 130
SFR Definition 24.1. SCON0: Serial Port 0 Control .................................................... 142
SFR Definition 24.2. SBUF0: Serial (UART0) Port Data Buffer .................................. 143
Rev. 1.2 12
C8051T600/1/2/3/4/5/6
SFR Definition 25.1. CKCON: Clock Control .............................................................. 146
SFR Definition 25.2. TCON: Timer Control ................................................................. 151
SFR Definition 25.3. TMOD: Timer Mode ................................................................... 152
SFR Definition 25.4. TL0: Timer 0 Low Byte ............................................................... 153
SFR Definition 25.5. TL1: Timer 1 Low Byte ............................................................... 153
SFR Definition 25.6. TH0: Timer 0 High Byte ............................................................. 154
SFR Definition 25.7. TH1: Timer 1 High Byte ............................................................. 154
SFR Definition 25.8. TMR2CN: Timer 2 Control ......................................................... 157
SFR Definition 25.9. TMR2RLL: Timer 2 Reload Register Low Byte .......................... 158
SFR Definition 25.10. TMR2RLH: Timer 2 Reload Register High Byte ...................... 158
SFR Definition 25.11. TMR2L: Timer 2 Low Byte ....................................................... 158
SFR Definition 25.12. TMR2H Timer 2 High Byte ....................................................... 159
SFR Definition 26.1. PCA0CN: PCA Control .............................................................. 173
SFR Definition 26.2. PCA0MD: PCA Mode ................................................................ 174
SFR Definition 26.3. PCA0CPMn: PCA Capture/Compare Mode .............................. 175
SFR Definition 26.4. PCA0L: PCA Counter/Timer Low Byte ...................................... 176
SFR Definition 26.5. PCA0H: PCA Counter/Timer High Byte ..................................... 176
SFR Definition 26.6. PCA0CPLn: PCA Capture Module Low Byte ............................. 177
SFR Definition 26.7. PCA0CPHn: PCA Capture Module High Byte ........................... 177
C2 Register Definition 27.1. C2ADD: C2 Address ...................................................... 178
C2 Register Definition 27.2. DEVICEID: C2 Device ID ............................................... 179
C2 Register Definition 27.3. REVID: C2 Revision ID .................................................. 179
C2 Register Definition 27.4. DEVCTL: C2 Device Control .......................................... 180
C2 Register Definition 27.5. EPCTL: EPROM Programming Control Register ........... 180
C2 Register Definition 27.6. EPDAT: C2 EPROM Data .............................................. 181
C2 Register Definition 27.7. EPSTAT: C2 EPROM Status ......................................... 181
C2 Register Definition 27.8. EPADDRH: C2 EPROM Address High Byte .................. 182
C2 Register Definition 27.9. EPADDRL: C2 EPROM Address Low Byte ................... 182
C2 Register Definition 27.10. CRC0: CRC Byte 0 ...................................................... 183
C2 Register Definition 27.11. CRC1: CRC Byte 1 ...................................................... 183
C2 Register Definition 27.12. CRC2: CRC Byte 2 ...................................................... 184
C2 Register Definition 27.13. CRC3: CRC Byte 3 ...................................................... 184
C8051T600/1/2/3/4/5/6
13 Rev. 1.2
1. System Overview
C8051T600/1/2/3/4/5/6 devices are fully integrated, mixed-signal, system-on-a-chip MCUs. Highlighted
features are listed below. Refer to Table 2.1 for specific product feature selection and part ordering num-
bers.
High-speed pipelined 8051-compatible microcontroller core (up to 25 MIPS)
In-system, full-speed, non-intrusive debug interface (on-chip)
C8051F300 ISP Fl ash device is available for quick in-system code development
10-bit 500 ksps Single-ended ADC with analog multiplexer and integrated temperature sensor
Precision calibrated 24.5 MHz internal oscillator
8 k, 4 k, 2 k or 1.5 kB of on-chip Byte-Programmable EPROM—(512 bytes are reserved on 8k version)
256 or 128 bytes of on-chip RAM
SMBus/I2C, and ART serial interfaces implemented in hardware
Three general-purpose 16-bit timers
Programmable Counter/Timer Array (PCA) with three capture/compare modules and Watchdog Timer function
On-chip Power-On Reset and Supply Monitor
On-chip Voltage Comparator
8 or 6 Port I/O
With on-chip power-on reset, VDD monitor , watchdog timer, and clock oscillator , the C8051T600/1/2/3/4/5/6
devices are truly stand-alone, system-on-a-chip solutions. User software has complete control of all
peripherals an d may individually shut down any or all peripherals for power savings.
Code written for the C8051T600/1/2/3/4/5/6 family of processors will run on the C8051F300 Mixed-Signal
ISP Flash microcontroller, providing a quick, cost-effective way to develop code without requiring special
emulator circuitry. The C8051T600/1/2/3/4/5/6 processors include Silicon Laboratories’ 2-Wire C2 Debug
and Programming interface, which allows non-intrusive (uses no on-chip resources), full speed, in-circuit
debugging using the produ ction MCU insta lled in the final application. Th is debug lo gic supports inspection
of memory, viewing and modificatio n of special function registers, setting breakpoints, single stepping, and
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 without occu-
pying package pins.
Each device is specified for 1.8–3.6 V operation over the industrial temperature range (–45 to +85 °C). An
internal LDO is used to supply the processor core voltage at 1.8 V. The Port I/O and RST pins are tolerant
of input signals up to 5 V. See Table 2.1 for ordering information. Block diagrams of the devices in the
C8051T600/1/2/3/4/5/6 family are shown in Figure 1.1, Figure 1.2, and Figure 1.3.
Rev. 1.2 14
C8051T600/1/2/3/4/5/6
Figure 1.1. C8051T600/2/4 Block Diagram
Figure 1.2. C8051T601/3/5 Block Diagram
System Clock
Configuration
Debug /
Programming
Hardware
Port 0
Drivers
Digital Peripherals
UART
Timers 0,
1, and 2
PCA/
WDT
SMBus
Priority
Crossbar
Decoder
P0.0/VREF
P0.1
P0.2/VPP
P0.3/EXTCLK
P0.4/TX
P0.5/RX
P0.6
P0.7/C2D
Crossbar Control
AIN0 - AIN7
Analog Peripherals
10-bit
500ksps
ADC
A
M
U
XTemp
Sensor
Comparator
+
-
VREFVDD
CP0
VDD
Port I/O Configuration
CIP-51 8051
Controller Core
2k/4k/8k Byte
EPROM Program
Memory
256 byte SRAM
External
Clock
Circuit
Precision
Internal
Oscillator
EXTCLK
Power On
Reset
Reset
C2D
VDD
GND
Power Net
C2CK/RST
SFR
Bus
SYSCLK
System Clock
Configuration
Debug /
Programming
Hardware
Port 0
Drivers
Digital Peripherals
UART
Timers 0,
1, and 2
PCA/
WDT
SMBus
Priority
Crossbar
Decoder
P0.0
P0.1
P0.2/VPP
P0.3/EXTCLK
P0.4/TX
P0.5/RX
P0.6
P0.7/C2D
Crossbar Control
Analog Peripherals
Comparator
+
-
CP0
Port I/O Configuration
CIP-51 8051
Controller Core
2k/4k/8k Byte
EPROM Program
Memory
256 byte SRAM
External
Clock
Circuit
Precision
Internal
Oscillator
EXTCLK
Power On
Reset
Reset
C2D
VDD
GND
Power Net
C2CK/RST
SFR
Bus
SYSCLK
C8051T600/1/2/3/4/5/6
15 Rev. 1.2
Figure 1.3. C8051T606 Block Diagram
System Clock
Configuration
Debug /
Programming
Hardware
Port 0
Drivers
Digital Peripherals
UART
Timers 0,
1, and 2
PCA/
WDT
SMBus
Priority
Crossbar
Decoder
P0.1
P0.2/VPP
P0.3/EXTCLK
P0.4/TX
P0.5/RX
P0.7/C2D
Crossbar Control
Analog Peripherals
Comparator
+
-
CP0
Port I/O Configuration
CIP-51 8051
Controller Core
1.5 k Byte EPROM
Program Memory
128 Byte SRAM
External
Clock
Circuit
Precision
Internal
Oscillator
EXTCLK
Power On
Reset
Reset
C2D
VDD
GND
Power Net
C2CK/RST
SFR
Bus
SYSCLK
C8051T600/1/2/3/4/5/6
16 Rev. 1.2
2. Ordering Information
Table 2.1. Product Selection Guide
Part Number
MIPS (Peak)
OTP EPROM (Bytes)
RAM (Bytes)
Calibrated Internal Oscillator
SMBus/I2C
UART
Timers (16-bit)
Programmable Counter Array
Digital Port I/Os
10-bit 500ksps ADC
Temperature Senso r
Analog Comparators
Lead-Free (ROHS Compliant)2
Package
C8051T600-GM 25 8k1256YYY3Y8YY1Y QFN-11
C8051T600-GS 25 8k1256YYY3Y8YY1YSOIC-14
C8051T601-GM 25 8k1256YYY3Y8——1Y QFN-11
C8051T601-GS 25 8k1256YYY3Y8——1Y SOIC-14
C8051T602-GM 25 4k 256 Y Y Y 3 Y 8 Y Y 1 Y QFN-11
C8051T602-GS 25 4k 256 Y Y Y 3 Y 8 Y Y 1 Y SOIC-14
C8051T603-GM 25 4k 256 Y Y Y 3 Y 8 — — 1 Y QFN-11
C8051T603-GS 25 4k 256 Y Y Y 3 Y 8 — — 1 Y SOIC-14
C8051T604-GM 25 2k 256 Y Y Y 3 Y 8 Y Y 1 Y QFN-11
C8051T604-GS 25 2k 256 Y Y Y 3 Y 8 Y Y 1 Y SOIC-14
C8051T605-GM 25 2k 256 Y Y Y 3 Y 8 — — 1 Y QFN-11
C8051T605-GS 25 2k 256 Y Y Y 3 Y 8 — — 1 Y SOIC-14
C8051T606-GM 25 1.5k 128 Y Y Y 3 Y 6 — — 1 Y QFN-11
C8051T606-GT 25 1.5k 128 Y Y Y 3 Y 6 — — 1 Y MSOP-10
C8051T606-ZM 25 1.5k 128 Y Y Y 3 Y 6 — — 1 Y QFN-10
Notes:
1. 512 Bytes Reserved
2. Lead Finish is 100% Matte Tin (Sn)
C8051T600/1/2/3/4/5/6
17 Rev. 1.2
3. Pin Definitions
Table 3.1. Pin Definitions for the C8051T600/1/2/3/4/5
Name QFN11
Pin SOIC14
Pin Type Description
VDD 3 7 Power Supply Voltage.
GND 11 3 Ground.
RST /
C2CK
814D I/O
D I/O
Device Reset. Open-dr ain out put of internal POR or VDD monitor.
Clock signal for the C2 Debug Interface.
P0.7 /
C2D
10 2 D I/O or
A In
D I/O
Port 0.7.
Bi-directional data signal for the C2 Debug Interface.
P0.0 /
VREF
1 5 D I/O or
A In
A In
Port 0.0.
External VREF input.
P0.1 2 6 D I/O or
A In Port 0.1.
P0.2 /
VPP
4 8 D I/O or
A In
A In
Port 0.2.
VPP Programming Supply Voltage.
P0.3 /
EXTCLK
5 10 D I/O or
A In
A I/O or
D In
Port 0.3.
External Clock Pin. This pin can be used as the external clock
input for CMOS, capacitor, or RC oscillator configurations.
P0.4 6 12 D I/O or
A In Port 0.4.
P0.5 7 13 D I/O or
A In Port 0.5.
P0.6 /
CNVSTR
9 1 D I/O or
A In
D In
Port 0.6.
ADC0 External Convert Start Input.
NC — 4,9,11 No Connection.
Rev. 1.2 18
C8051T600/1/2/3/4/5/6
Table 3.2. Pin Definitions for the C8051T606
Name QFN11
Pin MSOP10
Pin QFN10
Pin Type Description
VDD 3 3 2 Power Supply Voltage.
GND 9 9 8 Ground (Required).
GND* 11 — — Ground (Optional).
RST /
C2CK
887D I/O
D I/O
Device Reset. Open-drain output of internal POR or
VDD monitor.
Clock signal for the C2 Debug Interface.
P0.7 /
C2D
10 10 9 D I/O or
A In
D I/O
Port 0.7.
Bi-directional data signal for the C2 Debug Interface.
P0.1 2 2 1 D I/O or
A In Port 0.1.
P0.2 /
VPP
4 4 3 D I/O or
A In
A In
Port 0.2.
VPP Programming Supply Voltage.
P0.3 /
EXTCLK
5 5 4 D I/O or
A In
A I/O or
D In
Port 0.3.
External Clock Pin. This pin can be used as the exter-
nal clock input for CMOS, capacitor, or RC oscillator
configurations.
P0.4 6 6 5 D I/O or
A In Port 0.4.
P0.5 7 7 6 D I/O or
A In Port 0.5.
NC 1 1 10 No Connection.
C8051T600/1/2/3/4/5/6
19 Rev. 1.2
Figure 3.1. C8051T600/1/2/3/4/5-GM QFN11 Pinout Diagram (Top View)
Figure 3.2. C8051T600/1/2/3/4/5-GS SOIC14 Pinout Diagram (Top View)
1
2
3
4
56
7
8
9
10
11
P0.0 / VREF
P0.1
VDD
P0.2 / VPP
P0.3 / EXTCLK P0.4
P0.5
P0.6 /
CNVSTR
P0.7 / C2D
GND RST / C2CK
TOP VIEW
2
1
4
3
5
6
7
13
14
11
12
10
9
8
TOP VIEW
P0.7 / C2D
P0.6 / CNVSTR
GND
NC
P0.0 / VREF
P0.1
VDD
P0.3 / EXTCLK
P0.5
RST / C2CK
P0.4
NC
NC
P0.2 / VPP
Rev. 1.2 20
C8051T600/1/2/3/4/5/6
Figure 3.3. C8051T606-GM QFN11 Pinout Diagram (Top View)
Figure 3.4. C8051T606-GT MSOP10 Pinout Diagram (Top View)
1
2
3
4
56
7
8
9
10
11
NC
P0.1
VDD
P0.2 / VPP
P0.3 / EXTCLK P0.4
P0.5
GND
P0.7 / C2D
GND*
(Optional) RST / C2CK
TOP VIEW
2
1
4
3
5
9
10
7
8
6
TOP VIEW
P0.1
NC
VDD
P0.2 / VPP
P0.3 / EXTCLK P0.4
GND
RST / C2CK
P0.5
P0.7 / C2D
C8051T600/1/2/3/4/5/6
21 Rev. 1.2
Figure 3.5. C8051T606-ZM QFN10 Pinout Diagram (Top View)
5
10
6
7
8
9
1
2
3
4
P0.1
VDD
P0.2 / VPP
P0.3 / EXTCLK
P0.4
P0.5
GND
P0.7 / C2D
RST / C2CK
TOP VIEW
NC
C8051T600/1/2/3/4/5/6
22 Rev. 1.2
4. QFN-11 Package Specifications
Figure 4.1. QFN-11 Package Drawing
Table 4.1. QFN-11 Package Dimensions
Dimension Min Nom Max Dimension Min Nom Max
A 0.80 0.90 1.00 E 3.00 BSC
A1 0.03 0.07 0.11 E2 2.20 2.25 2.30
A3 0.25 REF L 0.45 0.55 0.65
b 0.18 0.25 0.30 aaa — — 0.15
D 3.00 BSC bbb — — 0.15
D2 1.30 1.35 1.40 ddd — — 0.05
e 0.50 BSC eee — — 0.08
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-243, variation VEED except for
custom features D2, E2, and L which are toleranced per supplier designation.
4. Recommended card reflow profile is per the JEDEC/IPC J-STD-020 specification for Small Body
Components.
Rev. 1.2 23
C8051T600/1/2/3/4/5/6
Figure 4.2. QFN-11 PCB Land Pattern
Table 4.2. QFN-11 PCB Land Pattern Dimensions
Dimension Min Max Dimension Min Max
C1 2.75 2.85 X2 1.40 1.50
C2 2.75 2.85 Y1 0.65 0.75
E 0.50 BSC Y2 2.30 2.40
X1 0.20 0.30
Notes:
General
1. All dimensions shown are in millimeters (mm) unl ess otherwise noted.
2. This Land Pattern Design is based on the IPC -7 351 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 60 μm 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 0.125 mm (5 mils).
6. The ratio of sten ci l aperture to land pad size should be 1:1 fo r al l perime t er pi n s.
7. A 3 x 1 arra y of 1.30 x 0.60 mm openings on 0.80 mm 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-020 specification for
Small Body Components.
C8051T600/1/2/3/4/5/6
24 Rev. 1.2
5. SOIC-14 Package Specifications
Figure 5.1. SOIC-14 Package Drawing
Table 5.1. SOIC-14 Package Dimensions
Dimension Min Nom Max Dimension Min Nom Max
A — — 1.75 L 0.40 — 1.27
A1 0.10 — 0.25 L2 0.25 BSC
b 0.33 — 0.51 θ0° — 8°
c 0.17 — 0.25 aaa 0.10
D 8.65 BSC bbb 0.20
E 6.00 BSC ccc 0.10
E1 3.90 BSC ddd 0.25
e 1.27 BSC
Notes:
1. All dimensions shown are in millimeters (mm).
2. Dimensioning and Tolerancing per ANSI Y14.5M-1994.
3. This drawing conforms to JEDEC outline MS012, variation AB.
4. Recommended card reflow profile is per the JEDEC/IPC J-STD-020 specification for Small Body
Components.
Rev. 1.2 25
C8051T600/1/2/3/4/5/6
Figure 5.2. SOIC-14 Recommended PCB Land Pattern
Table 5.2. SOIC-14 PCB Land Pattern Dimensions
Dimension Min Max Dimension Min Max
C1 5.30 5.40 X1 0.50 0.60
E 1.27 BSC Y1 1.45 1.55
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 60 μm 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 0.125 mm (5 mils).
6. The ratio of stencil aperture to land pad size should be 1:1 for all perimeter pads.
Card Assembly
7. A No-Clean, Type-3 solder paste is recommended.
8. The recommended card reflow profile is per the JEDEC/IPC J-STD-020 specification for Small
Body Components.
C8051T600/1/2/3/4/5/6
26 Rev. 1.2
6. MSOP-10 Package Specifications
Figure 6.1. MSOP-10 Package Drawing
Table 6.1. MSOP-10 Packag e Dimensions
Dimension Min Nom Max Dimension Min Nom Max
A — — 1.10 e 0.50 BSC
A1 0.00 — 0.15 L 0.40 0.60 0.80
A2 0.75 0.85 0.95 L2 0.25 BSC
b 0.17 — 0.33 θ0° — 8°
c 0.08 — 0.23 aaa — — 0.20
D 3.00 BSC bbb — — 0.25
E 4.90 BSC ccc — — 0.10
E1 3.00 BSC ddd — — 0.08
Notes:
1. All dimensions shown are in millimeters (mm).
2. Dimensioning and Tolerancing per ANSI Y14.5M-1994.
3. This drawing conforms to JEDEC outline MO-187, Variation “BA”.
4. Recommended card reflow profile is per the JEDEC/IPC J-STD-020 specification for Small Body
Components.
Rev. 1.2 27
C8051T600/1/2/3/4/5/6
Figure 6.2. MSOP-10 PCB Land Pattern
Table 6.2. MSOP-10 PCB Land Pattern Dimensions
Dimension Min Max Dimension Min Max
C1 4.40 REF X1 — 0.30
E 0.50 BSC Y1 1.40 REF
G1 3.00 — Z1 — 5.80
Notes:
General
1. All dimensions shown are in millimeters (mm) unl ess otherwise noted.
2. Dimensioning and Tolerancing per ASME Y14.5M-1994.
3. This Land Pattern Design is based on the IPC -7 351 guidelines.
4. All dimensions shown are at Maximum Material Condition (MMC). Least Material Condition
(LMC) is calculated based on a Fabrication Allowance of 0.05 mm.
Solder Mask Design
5. All metal pads are to be non-solder mask defined (NSMD). Clearance between the solder
mask and the metal pad is to be 60 μm minimum, all the way around the pad.
Stencil Design
6. A stainless steel, laser-cut and electro-polished stencil with trapezoidal walls should be used
to assure good solder paste release.
7. The stencil thickness should be 0.125 mm (5 mils).
8. The ratio of stencil aperture to land pad size should be 1:1 for all perimeter pads.
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-020 specification for
Small Body Components.
C8051T600/1/2/3/4/5/6
28 Rev. 1.2
7. QFN-10 Package Specifications
Figure 7.1. QFN-10 Package Drawing
Tab le 7.1. QFN-10 Package Dimensions
Dimension Min Nom Max Dimension Min Nom Max
A 0.70 0.75 0.80 L 0.55 0.60 0.65
A1 0.00 — 0.05 L1 — — 0.15
b 0.18 0.25 0.30 aaa — — 0.10
D 2.00 BSC. bbb — — 0.10
e 0.50 BSC. ccc — — 0.05
E 2.00 BSC. ddd — — 0.08
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 outline MO-220, variation WCCD-5 except for feature L which
is toleranced per supplier designation.
4. Recommended card reflow profile is per the JEDEC/IPC J-STD-020 specification for Small Body
Components.
Rev. 1.2 29
C8051T600/1/2/3/4/5/6
Figure 7.2. QFN-10 PCB Land Pattern
Table 7.2. QFN-10 PCB Land Pattern Dimensions
Dimension Min Max Dimension Min Max
e 0.50 BSC. X1 0.20 0.30
C1 1.70 1.80 Y1 0.85 0.95
C2 1.70 1.80
Notes:
General
1. All dimensions shown are in millimeters (mm) unl ess otherwise noted.
2. Dimensioning and Tolerancing is per the ANSI Y14.5M-1994 specification.
3. This Land Pattern Design is based on IPC-SM-782 guidelines.
4. All dimensions shown are at Maximum Material Condition (MMC). Least Material Condition
(LMC) is calculated based on a Fabrication Allowance of 0.05mm.
Solder Mask Design
5. All metal pads are to be non-solder mask defined (NSMD). Clearance between the solder
mask and the metal pad is to be 60 μm minimum, all the way around the pad.
Stencil Design
6. A stainless steel, laser-cut and electro-polished stencil with trapezoidal walls should be used
to assure good solder paste release.
7. The stencil thickness should be 0.125 mm (5 mils).
8. The ratio of sten ci l aperture to land pad size should be 1:1 fo r the pe ri me te r pads.
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-020 specification for
Small Body Components.
C8051T600/1/2/3/4/5/6
30 Rev. 1.2
8. Electrical Characteristics
8.1. Absolute Maximum Specifications
Table 8.1. Absolute Maximum Ratings
Parameter Conditions Min Typ Max Units
Ambient temperature under bias –55 — 125 °C
Storage temperature –65 — 150 °C
Voltage on RST or any Port I/O pin
(except VPP during progr am m i ng ) with
respect to GND
VDD > 2.2 V
VDD < 2.2 V –0.3
–0.3 —
—5.8
VDD + 3.6 V
V
Voltage on VPP with res pect to GND
during a programming operation VDD > 2.4 V –0.3 — 7.0 V
Duration of High-voltage on VPP pin
(cumulative) VPP > (VDD + 3.6 V) — — 10 s
Voltage on VDD with respect to GND Regulator in Normal Mode
Regulator in Bypass Mode –0.3
–0.3 —
—4.2
1.98 V
V
Maximum tota l current through VDD or
GND ——500mA
Maximum output curren t sunk or
sourced by RST or any Port pin ——100mA
Note: S tresses 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 devi ces at th ose or any other cond itions above
those indicated in the operation list ings of this specification is not implied. Exposure to maximum rating
conditions for extended periods may affect device reliability.
Rev. 1.2 31
C8051T600/1/2/3/4/5/6
8.2. Electrical Characteristics
Table 8.2. Global Electrical Characteristics
–40 to +85 °C, 25 MHz system clock unless othe rwise specified.
Parameter Conditions Min Typ Max Units
Supply Voltage (Note 1) Regulator in Normal Mode
Regulator in Bypa ss Mode 1.8
1.7 3.0
1.8 3.6
1.9 V
V
C8051T600/1/2/3/4/5 Digital Sup-
ply Current with CPU Active VDD = 1.8 V, Clock = 25 MHz
VDD = 1.8 V, Clock = 1 MHz
VDD = 3.0 V, Clock = 25 MHz
VDD = 3.0 V, Clock = 1 MHz
—
—
—
—
4.3
2.0
5.0
2.4
6.0
—
6.0
—
mA
mA
mA
mA
C8051T600/1/2/3/4/5 Digital Sup-
ply Current with CPU Inactive (not
accessing EPROM)
VDD = 1.8 V, Clock = 25 MHz
VDD = 1.8 V, Clock = 1 MHz
VDD = 3.0 V, Clock = 25 MHz
VDD = 3.0 V, Clock = 1 MHz
—
—
—
—
1.7
0.5
1.8
0.6
2.5
—
2.6
—
mA
mA
mA
mA
C8051T600/1/2/3/4/5 Digital Sup-
ply Current (shutdown) Oscillator not running (stop mode),
Internal Regulator Off —1—µA
Oscillator not running (stop or sus-
pend mode), Internal Regulator On —450— µA
C8051T606 Digital Supply Current
with CPU Active VDD = 1.8 V, Clock = 25 MHz
VDD = 1.8 V, Clock = 1 MHz
VDD = 3.0 V, Clock = 25 MHz
VDD = 3.0 V, Clock = 1 MHz
—
—
—
—
4.6
1.9
5.0
1.9
6.0
—
6.0
—
mA
mA
mA
mA
C8051T606 Digital Supply Current
with CPU Inactive (not accessing
EPROM)
VDD = 1.8 V, Clock = 25 MHz
VDD = 1.8 V, Clock = 1 MHz
VDD = 3.0 V, Clock = 25 MHz
VDD = 3.0 V, Clock = 1 MHz
—
—
—
—
1.7
0.35
1.8
0.36
2.5
—
2.6
—
mA
mA
mA
mA
C8051T606 Digital Supply Current
(shutdown) Oscillator not running (stop mode),
Internal Regulator Off —1—µA
Oscillator not running (stop or sus-
pend mode), Internal Regulator On —300— µA
Digital Supply RAM Data Retention
Voltage —1.5— V
Specified Operating Temperature
Range –40 — +85 °C
SYSCLK (system clock frequency) (Note 2) 0 — 25 MHz
Notes:
1. Analog performance is not guaranteed when VDD is below 1.8 V.
2. SYSCLK must be at least 32 kHz to enable debugging.
3. Supply current parameters specified with Memory Po wer Controller enabled.
C8051T600/1/2/3/4/5/6
32 Rev. 1.2
Tsysl (SYSCLK low time) 18 — — ns
Tsysh (SYSCLK high time) 18 — — ns
Table 8.2. Global Electrical Characteristics
–40 to +85 °C, 25 MHz system clock unless othe rwise specified.
Parameter Conditions Min Typ Max Units
Notes:
1. Analog performance is not guaranteed when VDD is below 1.8 V.
2. SYSCLK must be at least 32 kHz to enable debugging.
3. Supply current parameters specified with Memory Po wer Controller enabled.
Rev. 1.2 33
C8051T600/1/2/3/4/5/6
Table 8.3. Port I/O DC Electrical Characteristics
VDD = 1.8 to 3.6 V, –40 to +85 °C unless otherwise specified.
Parameters Conditions Min Typ Max Units
Output High Voltage IOH = –3 mA, Port I/O push-pull
IOH = –10 µA, Port I/O push-pull
IOH = –10 mA, Port I/O push-pull
VDD - 0.3
VDD - 0.1
—
—
—
VDD - 0.5
—
—
—
V
V
V
Output Low Voltage IOL = 8.5 mA
IOL = 10 µA
IOL = 25 mA
—
—
—
—
—
0.4 x VDD
0.6
0.1
—
V
V
V
Input High Voltage 0.7 x VDD ——V
Input Low Vo ltage — — 0.6 V
Input Leakag e
Current Weak Pullup Off
Weak Pullup On, VIN = 0 V –1
——
25 1
50 µA
µA
C8051T600/1/2/3/4/5/6
34 Rev. 1.2
Table 8.4. Reset Electrical Characteristics
–40 to +85 °C unless otherwise specified.
Parameter Conditions Min Typ Max Units
RST Output Low Voltage IOL = 8.5 mA,
VDD = 1.8 V to 3.6 V ——0.6V
RST Input High Voltage 0.75 x VDD ——V
RST Input Low Voltage — — 0.6 VDD
RST Input Pullup Current RST = 0.0 V — 25 50 µA
VDD POR Ramp Time — — 1 ms
VDD Monitor Threshold (VRST) 1.7 1.75 1.8 V
Missing Clock Detector
Timeout Time from last system clock
rising edge to reset initiation 400 625 900 µs
Reset Time Delay Delay between release of any
reset source and code
execution at location 0x0000
——60µs
Minimum RST Low Time to
Generate a System Reset 15 — — µs
VDD Monitor Turn-on Time VDD = VRST - 0.1 V — 50 — µs
VDD Monitor Supply Current — 20 30 µA
Table 8.5. Internal Voltage Regulator Electrical Characteristics
–40 to +85 °C unless otherwise specified.
Parameter Conditions Min Typ Max Units
Input Voltage Range 1.8 — 3.6 V
Bias Current Normal Mode — 30 50 µA
Table 8.6. EPROM Electrical Characteristics
Parameter Conditions Min Typ Max Units
EPROM Size C8051T600/1
C8051T602/3
C8051T604/5
C8051T606
8192*
4096
2048
1536
—
—
—
—
—
—
—
—
bytes
bytes
bytes
bytes
Write Cycle Time (pe r Byte) 105 155 205 µs
Programming Voltage (VPP) C8051T600/1/2/3/4/5 6.25 6.5 6.75 V
Programming Voltage (VPP) C8051T606 5.75 6.0 6.25 V
Note: 512 bytes at location 0x1E00 to 0x1FFF are not available for program storage
Rev. 1.2 35
C8051T600/1/2/3/4/5/6
Table 8.7. Internal High-Frequency Oscillator Electrica l Characteristics
VDD = 1.8 to 3.6 V; TA = –40 to +85 °C unless otherwise specified. Use factory-calibrated settings.
Parameter Conditions Min Typ Max Units
Oscillator Frequency IFCN = 11b 24 24.5 25 MHz
Oscillator Supply Current
(from VDD)25 °C, VDD = 3.0 V,
OSCICN.2 = 1 — 450 700 µA
Power Supply Variance Constant Temperature — ±0.02 — %/V
Temperature Variance Constant Supply — ±20 — ppm/°C
Table 8.8. Temperature Sensor Electrical Characteristics
VDD = 3.0 V, –40 to +85 °C unless otherwise specified.
Parameter Conditions Min Typ Max Units
Linearity — ±0.5 — °C
Slope — 3.2 — mV/°C
Slope Error* — ±80 — µV/°C
Offset Temp = 0 °C — 903 — mV
Offset Error* Temp = 0 °C — ±10 — mV
Note: Represents one standard deviation from the mean.
Table 8.9. Voltage Reference Electrical Characteristics
VDD = 3.0 V; –40 to +85 °C unless otherwise specified.
Parameter Conditions Min Typ Max Units
Input Voltage Range 0 — VDD V
Input Current Sample Rate = 500 ksps; VREF = 2.5 V — 12 — µA
C8051T600/1/2/3/4/5/6
36 Rev. 1.2
Table 8.10. ADC0 Electrical Characteristics
VDD = 3.0 V, VREF = 2.40 V (REFSL=0), –40 to +85 °C unless otherwise specified.
Parameter Conditions Min Typ Max Units
DC Accuracy
Resolution 10 bits
Integral Nonlinearity — ±0.5 ±1 LSB
Differential Nonlinearity Guaranteed Mo no to nic — ±0.5 ±1 LSB
Offset Error –2 0 2 LSB
Full Scale Error –2 0 2 LSB
Offset Temperature Coefficient — 45 — ppm/°C
Dynamic performance (10 kHz sine-wave single-ended input, 1 dB below Full Scale, 500 ksps)
Signal-to-Noise Plus Distortion 56 60 — dB
Total Harmonic Distortion Up to the 5th harmonic — 72 — dB
Spurious-Free Dynamic Range — –75 — dB
Conversion Rate
SAR Conversion Clock — — 8.33 MHz
Conversion Time in SAR Clocks 10-bit Mode
8-bit Mode 13
11 —
——
—clocks
clocks
Track/Hold Acquisition Time VDD > 2.0 V
VDD < 2.0 V 300
2.0 —
——
—ns
µs
Throughput Rate — — 500 ksps
Analog Inputs
ADC Input Voltage Range 0 — VREF V
Sampling Capacitance 1x Gain
0.5x Gain —
—5
3—
—pF
pF
Input Multiplexer Impedance — 5 — kΩ
Power Specifications
Power Supply Curr ent
(VDD supplied to ADC0) Operating Mode, 50 0 ksps — 600 900 µA
Power Supply Rejection — –70 — dB
Rev. 1.2 37
C8051T600/1/2/3/4/5/6
Table 8.11. Comparator Electrical Characteristics
VDD = 3.0 V, –40 to +85 °C unless otherwise noted.
Parameter Conditions Min Typ Max Units
Response Time:
Mode 0, Vcm* = 1.5 V CP0+ – CP0– = 100 mV — 240 — ns
CP0+ – CP0– = –100 mV — 240 — ns
Response Time:
Mode 1, Vcm* = 1.5 V CP0+ – CP0– = 100 mV — 400 — ns
CP0+ – CP0– = –100 mV — 400 — ns
Response Time:
Mode 2, Vcm* = 1.5 V CP0+ – CP0– = 100 mV — 650 — ns
CP0+ – CP0– = –100 mV — 1100 — ns
Response Time:
Mode 3, Vcm* = 1.5 V CP0+ – CP0– = 100 mV — 2000 — ns
CP0+ – CP0– = –100 mV — 5500 — ns
Common-Mode Rejection Ratio — 1 4 mV/V
Positive Hysteresis 1 CP0HYP1–0 = 00 — 0 1 mV
Positive Hysteresis 2 CP0HYP1–0 = 01 2 5 8 mV
Positive Hysteresis 3 CP0HYP1–0 = 10 5 10 14 mV
Positive Hysteresis 4 CP0HYP1–0 = 11 11 20 28 mV
Negative Hysteresis 1 CP0HYN1–0 = 00 — 0 1 mV
Negative Hysteresis 2 CP0HYN1–0 = 01 2 5 8 mV
Negative Hysteresis 3 CP0HYN1–0 = 10 5 10 14 mV
Negative Hysteresis 4 CP0HYN1–0 = 11 11 20 28 mV
Inverting or Non-Inverting Input
Voltage Range –0.25 — VDD + 0.25 V
Input Offset Voltage –7.5 — 7.5 mV
Power Specifications
Power Supply Rejection — 0.5 — mV/V
Powerup Time — 10 — µs
Supply Current at DC Mode 0 — 26 50 µA
Mode 1 — 10 20 µA
Mode 2 — 3 6 µA
Mode 3 — 0.5 2 µA
Note: Vcm is the common-mode voltage on CP0+ and CP0–.
C8051T600/1/2/3/4/5/6
38 Rev. 1.2
8.3. Typical Performance Curves
Figure 8.1. C8051T600/1/2/3/4/5 Normal Mode Supply Current vs. Frequency
(MPCE = 1)
Figure 8.2. C8051T606 Normal Mode Supply Current vs. Frequency (MPCE = 1)
0.0
1.0
2.0
3.0
4.0
5.0
6.0
0 5 10 15 20 25
SYSCLK (MHz)
IDD (mA)
VDD = 1. 8 V
VDD > 1.8 V
0.0
1.0
2.0
3.0
4.0
5.0
6.0
0 5 10 15 20 25
SYSCLK (MHz)
IDD (mA)
VDD = 1.8 V
VDD > 1.8 V
Rev. 1.2 39
C8051T600/1/2/3/4/5/6
Figure 8.3. C8051T600/1/2/3/4/5 Idle Mode Supply Current vs. Frequency
(MPCE = 1)
Figure 8.4. C8051T606 Idle Mode Digital Current vs. Frequency (MPCE = 1)
0.0
0.5
1.0
1.5
2.0
0 5 10 15 20 25
SYSCLK (MHz)
IDD (mA)
VDD = 1.8 V
VDD > 1.8 V
0.0
0.5
1.0
1.5
2.0
0 5 10 15 20 25
SYSCLK (MHz)
IDD (mA)
VDD = 1.8 V
VDD > 1.8 V
C8051T600/1/2/3/4/5/6
40 Rev. 1.2
9. 10-Bit ADC (ADC0, C8051T600/2/4 only)
ADC0 on the C8051T600/2/4 is a 500 ksps, 10-bit successive-approximation-register (SAR) ADC with
integrated tr ack-and-hold, a g ain st age progr ammable to 1 x or 0.5x, and a pr ogrammab le window detecto r.
The ADC is fully configurable under software control via Special Function Registers. The ADC may be con-
figured to measure various different signals using the analog multiplexer described in Section “9.5. ADC0
Analog Multiplexer (C8051T600/2/4 only)” on page 50. The voltage reference for the ADC is selected as
described in Section “11. Voltage Reference Options” on page 55. The ADC0 subsystem is enabled only
when the AD0EN bit in the ADC0 Control register (ADC0CN) is set to logic 1. The ADC0 subsystem is in
low power shutdown when this bit is logic 0.
Figure 9.1. ADC0 Functional Block Diagram
ADC0CF
AMP0GN0
AD08BE
AD0LJST
AD0SC0
AD0SC1
AD0SC2
AD0SC3
AD0SC4
10-Bit
SAR
ADC
REF
SYSCLK
ADC0H
32
ADC0CN
AD0CM0
AD0CM1
AD0CM2
AD0WINT
AD0BUSY
AD0INT
AD0TM
AD0EN
Timer 0 Overflow
Timer 2 Overflow
Timer 1 Overflow
Start
Conversion
000 AD0BUSY (W)
VDD
ADC0LTH
AD0WINT
001
010
011
100 CNVSTR Input
Window
Compare
Logic
101 Timer 3 Overflow
ADC0LTL
ADC0GTH ADC0GTL
ADC0L
AIN
From
AMUX0 X1 or
X0.5
AMP0GN0
Rev. 1.2 41
C8051T600/1/2/3/4/5/6
9.1. Output Code Formatting
The ADC measures the input volt age with refe rence to GND. The registers ADC0H and ADC0L contain the
high and low bytes of the output conversion cod e from the ADC at the completion of each conversio n. Data
can be right-justified or left-justified, depending on the setting of the AD0LJST bit. 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 bit s in the ADC0H and ADC0 L
registers are se t to 0.
9.2. 8-Bit Mode
Setting the ADC08BE bit in register ADC0CF to 1 w ill put the ADC in 8-bit mode. In 8-bit mode, only the 8
MSBs of data are converted, and the ADC0H register holds the results. The AD0LJST bit is ignored for 8-
bit mode. 8-bit conversions take two fewer SAR clock cycles than 10-bit conversio ns, so the co nversio n is
completed faster, and a 500 ksps sampling rate can be achieved with a slower SAR clock.
9.3. Modes of Operation
ADC0 has a maximum conversion speed of 500 ksps. The ADC0 conversion clock is a divided version of
the system clock, determined by the AD0SC bits in the ADC0CF register.
9.3.1. Starting a Conversion
A conversion can be initiated in one of six ways, dependin g on the programmed st ates of the ADC0 Start of
Conversion Mode bits (AD0CM2–0) in register ADC0CN. Conversions may be initiated by one of the fol-
lowing:
1. Writing a 1 to the AD0BUSY bit of register ADC0CN
2. A Timer 0 overflow (i.e., timed continuous conversions)
3. A Timer 2 overflow
4. A Timer 1 overflow
5. A rising edge on the CNVSTR input signal
6. A Timer 3 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 logic 1 and reset to logic 0 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 re gisters, ADC0H:ADC0L , when b it AD0INT
is logic 1. Note that when Timer 2 or Timer 3 overflows are used as the conversion source, Low Byte over-
flows are used if Timer 2/3 is in 8-bit mode. High byte overflows are used if Timer 2/3 is in 16-bit mode.
See Section “25. Timers” on page 145 for timer configuration.
Import ant 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 “22. Port Input/Ou tput” on page 106 for details on Port I/O configuration.
Input Voltage Right-Justified ADC0H:ADC0L
(AD0LJST = 0) Left-Justified ADC0H:ADC0L
(AD0LJST = 1)
VREF x 1023/1024 0x03FF 0xFFC0
VREF x 512/1024 0x0200 0x8000
VREF x 256/1024 0x0100 0x4000
0 0x0000 0x0000
C8051T600/1/2/3/4/5/6
42 Rev. 1.2
9.3.2. Tracking Modes
The AD0TM bit in register ADC0CN enables "delayed conversions", and will delay the actual conversion
start by three SAR clock cycles, during which time the ADC will continue to track the input. If AD0TM is left
at logic 0, a conversion will begin im mediately, w ithout the extra tracking time. For internal start-of-conver-
sion sources, the ADC will track anytime it is not performing a conversion. When the CNVSTR signal is
used to initiate conversions, ADC0 w ill track either when A D0TM is logic 1, or when AD0TM is logic 0 and
CNVSTR is held low. See Figure 9.2 for track and convert timing de tails. Delayed conversion mode is use-
ful when AMUX settings are freque ntly changed, due to the se ttling time requ irement s describe d in Section
“9.3.3. Settling Time Requirements” on p age 43.
Figure 9.2. 10-Bit ADC Track and Conversion Example Timing
Write '1' to AD0BUSY,
Timer 0, Timer 2, Timer 1 Overflow
(AD0CM[2:0]=000, 001, 010, 011)
AD0TM=1 Track Convert Track
AD0TM=0 Track Convert Track
SAR
Clocks
SAR
Clocks
B. ADC Timing for Internal Trigger Source
CNVSTR
(AD0CM[2:0]=1xx)
AD0TM=1
A. ADC Timing for External Trigger Source
Track Convert N/CAD0TM=0
Track Convert Track
*Conversion Ends at ris i ng edge of 12th clock in 8-bit Mode
*Conversion Ends at ris i ng edge of 15th clock in 8-bit Mode
*Conversion Ends at rising edge of 12th clock in 8-bit Mode
12345678910 11 12*13 14
12345678910 11 12 13 14 15*16 17
N/C
SAR Clocks
*Conversion Ends at ris i ng edge of 15th clock in 8-bit Mode
SAR
Clocks
12345678910 11 12 13 1415* 16 17
123456789
10 11 12* 13 14
Rev. 1.2 43
C8051T600/1/2/3/4/5/6
9.3.3. Settling Ti me 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 any series impedance, including the AMUX0 resistance, the
the ADC0 sampling capacitance, and the accuracy required for the conversion . Note that in de l ay ed tra ck-
ing mode, three SAR clocks are used for tracking at the start of every conversion. For many applications,
these three SAR clocks will meet the minimum tracking time requirements.
Figure 9.3 shows the equivalent ADC0 input circuit. The required ADC0 settling time for a given settling
accuracy (SA) may be approximated by Equation 9.1. See Table 8.10 for ADC0 minimum settling time
requirements as well as the mux impedance and sampling capacitor values.
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
RTOTAL is the sum of the AMUX0 resistance and any external source resistance.
n is the ADC resolution in bits (10).
Figure 9.3. ADC0 Equivalent Input Circuits
t2n
SA
-------
RTOTALCSAMPLE
×ln=
RMUX
CSAMPLE
RCInput= RMUX * CSAMPLE
MUX Select
Input Pin
Note: See el ectrical specificatio n tables for RMUX and CSAMPLE parameters.
C8051T600/1/2/3/4/5/6
44 Rev. 1.2
SFR Address = 0xBC
SFR Definition 9.1. ADC0CF: ADC0 Configuration
Bit76543210
Name AD0SC[4:0] AD0LJST AD08BE AMP0GN0
Type R/W R/W R/W R/W
Reset 11111001
Bit Name Function
7:3 AD0SC[4:0] ADC0 SAR Conversion Clock Period Bits.
SAR Conversion clock is derived from system clo ck b y the followin g eq uatio n, wher e
AD0SC refers to the 5-bit value held in bits AD0SC4–0. SAR Conversion clock
requirements are given in the ADC specification table.
Note: If the Memory Power Controller is enabled (MPCE = '1'), AD0SC must be set to at least
"00001" for proper ADC operation.
2AD0LJST
ADC0 Left Justify Select.
0: Data in ADC0H:ADC0L registers ar e rig ht-ju stif ied .
1: Data in ADC0H:ADC0L registers ar e left-justif i ed .
Note: The AD0LJST bit is onl y valid for 10-bit mode (AD08BE = 0).
1AD08BE
8-Bit Mode Enable.
0: ADC operates in 10-bit mode (normal).
1: ADC operates in 8-bit mode.
Note: When AD08BE is set to 1, the AD0LJST bit is ignored.
0AMP0GN0
ADC Gain Control Bit.
0: Gain = 0.5
1: Gain = 1
AD0SC SYSCLK
CLKSAR
-----------------------1–=
Rev. 1.2 45
C8051T600/1/2/3/4/5/6
SFR Address = 0xBE
SFR Address = 0xBD
SFR Definition 9.2. ADC0H: ADC0 Data Word MSB
Bit76543210
Name ADC0H[7:0]
Type R/W
Reset 00000000
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.
Note: In 8-bit mode AD0LJST is ignored, and ADC0H holds the 8-bit data word.
SFR Definition 9.3. ADC0L: ADC0 Data Word LSB
Bit76543210
Name ADC0L[7:0]
Type R/W
Reset 00000000
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. Bit s 5–0 will
read 000000b.
Note: In 8-bit mode AD0LJST is ignored, and ADC0L will read back 00000000b.
C8051T600/1/2/3/4/5/6
46 Rev. 1.2
SFR Address = 0xE8; Bit-Addressable
SFR Definition 9.4. ADC0CN: ADC0 Control
Bit76543210
Name AD0EN AD0TM AD0INT AD0BUSY AD0WINT AD0CM[2:0]
Type R/W R/W R/W R/W R/W R/W
Reset 00000000
Bit Name Function
7AD0EN
ADC0 Enable Bit.
0: ADC0 Disabled. ADC0 is in low-power shutdown.
1: ADC0 Enabled. ADC0 is active and ready for data conversions.
6AD0TM
ADC0 Track Mode Bit.
0: Normal Track Mode: When ADC0 is enabled, tr ack ing is cont inu o us un le ss 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 star t-of-conversion signal initiates three SAR clocks of additional
tracking, and then begins the conversion.
5AD0INT
ADC0 Conversion Complete Interrupt Flag.
0: ADC0 has not completed a da ta conversion since AD0INT was last cleared.
1: ADC0 has completed a data conversion.
4AD0BUSY
ADC0 Busy Bit. Read:
0: ADC0 conversion is not in
progress.
1: ADC0 conversion is in prog-
ress.
Write:
0: No Effect.
1: Initiates ADC0 Conversion if
AD0CM[2:0] = 000b
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[2:0] ADC0 Start of Conversion Mode Select.
000: ADC0 start-of-conversion source is write of 1 to AD0BUSY.
001: ADC0 start-of-conversion source is overflow of Timer 0.
010: ADC0 start-of-conversion source is overflow of Timer 2.
011: ADC0 start-of-conversion source is overflow of Timer 1.
100: ADC0 start-of-conversion source is rising edge of external CNVSTR.
101: ADC0 start-of-conversion source is overflow of Timer 3.
11x: Reserved.
Rev. 1.2 47
C8051T600/1/2/3/4/5/6
9.4. Programmable Window Detector
The ADC Programmable Window Detector continuously compares the ADC0 output registers to user-pro-
grammed limit s, and notifies the system whe n a desired co ndition is detected. This is especially ef fective i n
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 comp arison values. The window detector flag can be programmed to in dicate 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 Address = 0xC4
SFR Address = 0xC3
SFR Definition 9.5. ADC0GTH: ADC0 Greater-Than Data High Byte
Bit76543210
Name ADC0GTH[7:0]
Type R/W
Reset 11111111
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
Bit76543210
Name ADC0GTL[7:0]
Type R/W
Reset 11111111
Bit Name Function
7:0 ADC0GTL[7:0] ADC0 Greater-Than Data Word Low-Order Bits .
C8051T600/1/2/3/4/5/6
48 Rev. 1.2
SFR Address = 0xC6
SFR Address = 0xC5
SFR Definition 9.7. ADC0LTH: ADC0 Less-Than Data High Byte
Bit76543210
Name ADC0LTH[7:0]
Type R/W
Reset 00000000
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
Bit76543210
Name ADC0LTL[7:0]
Type R/W
Reset 00000000
Bit Name Function
7:0 ADC0LTL[7:0] ADC0 Less- T han Data Word Low-Order Bits.
Rev. 1.2 49
C8051T600/1/2/3/4/5/6
9.4.1. Window Detector Example
Figure 9.4 shows two example window comparisons for right-justified 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
(if 0x0040 < 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
(if ADC0H:ADC0L < 0x0040 or ADC0H:ADC0L > 0x0080). Figure 9.5 shows an example using left-justi-
fied data with the same comparison values.
Figure 9.4. ADC Window Compare Example: Right-Justified Data
Figure 9.5. ADC Window Compare Example: Left-Justified Data
0x03FF
0x0081
0x0080
0x007F
0x0041
0x0040
0x003F
0x0000
0
Input Voltage
(AIN - GND)
VREF x (1023/
1024)
VREF x (128/1024)
VREF x (64/1024)
AD0WINT=1
AD0WINT
not affected
AD0WINT
not affected
ADC0LTH:ADC0LTL
ADC0GTH:ADC0GTL
0x03FF
0x0081
0x0080
0x007F
0x0041
0x0040
0x003F
0x0000
0
Input Voltage
(AIN - GND)
VREF x (1023/
1024)
VREF x (128/1024)
VREF x (64/1024)
AD0WINT
not affected
AD0WINT=1
AD0WINT=1
ADC0H:ADC0L ADC0H:ADC0L
ADC0GTH:ADC0GTL
ADC0LTH:ADC0LTL
0xFFC0
0x2040
0x2000
0x1FC0
0x1040
0x1000
0x0FC0
0x0000
0
Input Voltage
(AIN - GND)
VREF x (1023/
1024)
VREF x (128/1024)
VREF x (64/1024)
AD0WINT=1
AD0WINT
not affected
AD0WINT
not affected
ADC0LTH:ADC0LTL
ADC0GTH:ADC0GTL
0xFFC0
0x2040
0x2000
0x1FC0
0x1040
0x1000
0x0FC0
0x0000
0
Input Voltage
(AIN - GND)
VREF x (1023/
1024)
VREF x (128/1024)
VREF x (64/1024)
AD0WINT
not affected
AD0WINT=1
AD0WINT=1
ADC0H:ADC0L ADC0H:ADC0L
ADC0LTH:ADC0LTL
ADC0GTH:ADC0GTL
C8051T600/1/2/3/4/5/6
50 Rev. 1.2
9.5. ADC0 Analog Multiplexer (C8051T600/2/4 only)
ADC0 on the C8051T600/2/4 uses an analog input multiplexer to select the positive input to the ADC. Any
of the following may be selected as the po sitive input: Port 0 I/O pins , the on-chip temper ature sensor, or
the positive power supply (V DD). The ADC0 input channel is selected in the AMX0SL register described in
SFR Definition 9.9.
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 the corresponding bit in register PnMDIN to ‘0’. To force the Crossbar to skip a Port pin, set the
corresponding bit in register XBR0 to ‘1’. See Section “22. Port Input/Output” on page 106 for more Port
I/O configuration details.
ADC0
Temp
Sensor
AMUX
VDD
AMX0SL
AMX0P3
AMX0P2
AMX0P1
AMX0P0
P0.0
P0.7
Rev. 1.2 51
C8051T600/1/2/3/4/5/6
SFR Address = 0xBB
SFR Definition 9.9. AMX0SL: AMUX0 Positive Channel Select
Bit76543210
Name AMX0P[3:0]
Type R/W R/W R/W R/W R/W
Reset 10000000
Bit Name Function
7:4 Unused Unused. Read = 1000b; Write = Don’t Care.
3:0 AMX0P[3:0] AMUX0 Positive Input Selection.
0000: P0.0
0001: P0.1
0010: P0.2
0011: P0.3
0100: P0.4
0101: P0.5
0110: P0.6
0111: P0.7
1000: Temp Sensor
1001: VDD
1010 – 1111: no input selected
C8051T600/1/2/3/4/5/6
52 Rev. 1.2
10. Temperature Sensor (C8051T600/2/4 only)
An on-chip temperature sensor is included on the C8051T600/2/4, which can be directly accessed via the
ADC multiplexer. To use the ADC to measure the temperature sensor, the ADC mux channel should be
configured to connect to the temperature sensor. The temperature sensor transfer function is shown in
Figure 10.1. The output voltage (VTEMP) is the positive ADC input when the ADC multiplexer is set cor-
rectly. The TEMPE bit in register REF0CN enables/disables the temperature sensor, as described in SFR
Definition 11.1. While disabled, the temperature sensor defaults to a high impedance state and any ADC
measurements performed on the sensor will result in meaningless data. Refer to Table 8.8 for the slope
and offset parameters of the temperature sensor.
Figure 10.1. Temperature Sensor Transfer Function
10.1. Calibration
The uncalibrated temperature sensor output is extremely linear and suitable for relative temperature mea-
surements (see Table 8.8 on page 35 for specifications). For absolute temperature measurements, offset
and/or gain calibration is recommended. A single-point offset measurement of the temperature sensor is
performed on each device during production test. The registers TOFFH and TOFFL, shown in SFR Defini-
tion 10.1 and SFR De finitio n 10.2 represent th e output of the ADC when reading the temperature sensor at
0 °C, and using the internal regulator as a voltage reference.
Figure 10.2 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.
Temperature
Voltage
VTEMP = (Slope x Temp
C) + Offset
Offset (V at 0° C)
Slope V/ (° C)
TempC = (VTEMP - Offset) / Slope
Rev. 1.2 53
C8051T600/1/2/3/4/5/6
Figure 10.2. Temperature Sensor Error with 1-Point Calibration at 0 °C
-40.00 -20.00 0.00 20.00 40.00 60.00 80.00
Temperature (degrees C)
Error (deg rees C)
-5.00
-4.00
-3.00
-2.00
-1.00
0.00
1.00
2.00
3.00
4.00
5.00
-5.00
-4.00
-3.00
-2.00
-1.00
0.00
1.00
2.00
3.00
4.00
5.00
C8051T600/1/2/3/4/5/6
54 Rev. 1.2
SFR Address = 0xA3
SFR Address = 0xA2
SFR Definition 10.1. TOFFH: Temperature Offset Measurement High Byte
Bit76543210
Name TOFF[9:2]
Type R/W
Reset Varies Varies Varies Varies Varies Varies Varies Varies
Bit Name Function
7:0 TOFF[9:2] Temperature Sensor Offset High Order Bits.
The temperature sensor offset registers represent the output of the ADC when mea-
suring the temperature sensor at 0 °C, with the voltage reference set to the internal
regulator. The temperature sensor offset information is left-justified. One LSB of this
measurement is equivalent to one LSB of the ADC output under the measurement
conditions.
SFR Definition 10.2. TOFFL: Temperature Offset Measurement Low Byte
Bit76543210
Name TOFF[1:0]
Type R/W RRRRRR
Reset VariesVaries000000
Bit Name Function
7:6 TOFF[1:0] Temperature Sensor Of fset Low Order Bits.
The temperature sensor offset registers represent the output of the ADC when mea-
suring the temperature sensor at 0 °C, with the voltage reference set to the internal
regulator. The temperature sensor offset information is left-justified. One LSB of this
measurement is equivalent to one LSB of the ADC output under the measurement
conditions.
5:0 Unused Unused. Read = 000000b; Write = Don’t Care.
C8051T600/1/2/3/4/5/6
55 Rev. 1.2
11. Voltage Reference Options
The voltage reference multiplexer for the ADC is configurable for use with an externally connected voltage
reference, the unregulated power supply voltage (VDD), or the regulated 1.8 V internal supply (see
Figure 11.1). The REFSL bit in the Reference Control register (REF0CN, SFR Definition 11.1) selects the
reference sour ce for the ADC. For a n external source, RE FSL should be set to 0 to select the VREF pin. To
use VDD as the reference source, REFSL should be set to 1. To override this selection and use the intern al
regulator as the reference source, the REGOVR bit can be set to 1. The electrical specifications for the
voltage reference circuit are given in Se ction “8. Electrical Characteristics” on page 30.
Important Note about the VREF Pin: When using an external voltage reference, the VREF pin should be
configured as an analog pin and skipped by the Digital Crossbar. Refer to Section “22. Port Input/Output”
on page 106 for the locatio n of the VREF pin, as well as details of how to configure the pin in analog mode
and to be skipped by the crossbar.
Figure 11.1. Voltage Reference Functional Block Diagram
To Analog Mux
VDD
VREF
R1
VDD External
Voltage
Reference
Circuit
GND
Temp Sensor
EN
0
1
REF0CN
REFSL
TEMPE
REGOVR
Recommended Bypass
Capacitors
+
4.7μF0.1μF
VREF
(to ADC)
0
1
Internal
Regulator
REGOVR
Rev. 1.2 56
C8051T600/1/2/3/4/5/6
SFR Address = 0xD1
SFR Definition 11.1. REF0CN: Reference Control
Bit76543210
Name REGOVR REFSL TEMPE
Type R R R R/W R/W R/W R R
Reset 00000000
Bit Name Function
7:5 Unused Unused. Read = 000b; Write = Don’t Care.
4REGOVR
Regulator Reference Override.
This bit “overrides” the REFSL bit, an d allows th e inte rnal regu lator to be used as a ref-
erence source.
0: The voltage reference source is selected by the REFSL bit.
1: The internal regulator is used as the volt age reference.
3 REFSL Voltage Reference Select.
This bit selects the ADCs voltage reference.
0: VREF pin used as voltage reference.
1: VDD used as voltage reference.
2 TEMPE Temperature Sensor Enable Bit.
0: Internal Tem p er at ur e Se nso r off.
1: Internal Tem p er at ur e Se nso r on.
1:0 Unused Unused. Read = 00b; Write = Don’t Care.
C8051T600/1/2/3/4/5/6
57 Rev. 1.2
12. Voltage Regulator (REG0)
C8051T600/1/2/3/4/5/6 devices include an internal voltage regulator (REG0) to regulate the internal core
supply to 1.8 V from a VDD supply of 1.8 to 3.6 V. Two power-saving modes are built into the regu lator to
help reduce current consumption in low-power applications. These modes are accessed through the
REG0CN register (SFR Definition 12.1). Electrical characteristics for the on-chip regulator are specified in
Table 8.5 on page 34.
If an external regulator is used to power the device, the internal regulator may be put into bypass mode
using the BYPASS bit. The internal regulator should never be placed in bypass mode unless an
external 1.8 V regulator is used to supply VDD. Doing so could cause permanent damage to the
device.
Under default conditions, when the device enters STOP mode the internal regulator will remain on. This
allows any enabled reset so urce to gene rate a reset for the device and bring the device out of ST OP 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 or
a full power cycle of the device are the only methods of generating a reset.
Rev. 1.2 58
C8051T600/1/2/3/4/5/6
SFR Address = 0xC7
SFR Definition 12.1. REG0CN: Voltage Regulator Control
Bit76543210
Name STOPCF BYPASS MPCE
Type R/W R/W R/W R/W R/W R/W R/W R/W
Reset 00000000
Bit Name Function
7STOPCF
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 do wn in STOP mode. Only the RST pin or power cycle can reset
the device.
6 BYPASS Bypass Internal Regulator.
This bit places the regu lator in bypass mode, turning off the regulator, and allowing the
core to run directly from the VDD supply pin.
0: Normal Mode—Regulator is on.
1: Bypass Mode—Regulator is off, and the microcontroller core operates directly from
the VDD supply voltage.
IMPORTANT: Bypass mode is for use with an external regulator as the supply
voltage only. Never place the regulator in bypass mode when the VDD supply
volt age is g reater than t he spe cifications g iven in Table 8.1 on page 30. Doing so
may cause permanent damage to the device.
5:1 Reserved Reserved. Must Write 00000b.
0MPCE
Memory Power Controller Enable.
This bit can help the system save power at slower system clock frequencies (about
2.0 MHz or less) by automatically shutting down the EPROM memory between clocks
when information is not being fetched from the EPROM memory.
0: Normal Mode—Memory power controller disabled (EPROM memory is always on).
1: Low Power Mode—Me mor y powe r co ntro ller enab led (EPROM me mor y tu rn s on /off
as needed).
Note: If an external clock source is used with the Memory Power Controller enabled, and the
clock frequency changes from slow (<2.0 MHz) to fast (> 2.0 MHz), the EPROM power
will turn on, and up to 20 clocks may be "skipped" to ensure that the EPROM power is
stable before reading memory.
C8051T600/1/2/3/4/5/6
59 Rev. 1.2
13. Comparator0
C8051T600/1/2/3/4/5/6 devices include an on-chip programmable voltage comparator, Comparator0,
shown in Figure 13.1.
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 “22. 4. Port I/O Initialization” on page 114) . Comparator0 may also be used as a reset source (see
Section “19.5. Comparator0 Reset” on page 94).
The Comparator0 inputs are selected by the comparator input multiplexer, as detailed in Section
“13.1. Comparator Multiplexer” on page 63.
Figure 13.1. 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 Compar ator output ( if assigne d to a Port I/O pin via the Cr ossbar ) defaults to the logic low state,
and the power supply to the comparator is turned off. See Section “22.3. Priority Crossbar Decoder” on
page 111 for details on configuring Comparator outputs via the digital Crossbar. Comparator inputs can be
VDD
CPT0CN
Reset
Decision
Tree
+
- Crossbar
Interrupt
Logic
Q
Q
SET
CLR
D
Q
Q
SET
CLR
D
(SYNCHRONIZER)
GND
CP0 +
CP0 -
CP0EN
CP0OUT
CP0RIF
CP0FIF
CP0HYP1
CP0HYP0
CP0HYN1
CP0HYN0
CPT0MD
CP0MD1
CP0MD0
CP0
Rising-edge
Interrupt Flag
CP0
Falling-edge
Interrupt Flag
CP0
CP0A
Comparator
Input Mux
Rev. 1.2 60
C8051T600/1/2/3/4/5/6
externally driven from –0.25 V to (VDD) + 0.25 V without damage or upset. The comple te Comp ar ator elec-
trical specifications are given in Section “8. Electrical Characteristics” on page 30.
The Comparator re sponse time may b e configured in software vi a the CPT0MD regis ter (see SFR Defini -
tion 13.2). Selecting a longer response time reduces the Comparator supply current.
Figure 13.2. 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 as 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 13.1). The amount of negative hysteresis volt a ge is deter mined by the setting s of
the CP0HYN bits. As shown in Figure 13.2, settings of 20, 10 or 5 mV 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-e dge and falling-edge output transitions. (For Inter-
rupt enable and priority control, see Section “17.1. MCU Interrupt Sources and Vectors” on page 81). The
CP0FIF flag is set to logic 1 upon a Comparator falling-edge occurrence, and the CP0RIF flag is set to
logic 1 upon the Comparator rising-edge occurrence. Once set, these bits remain set until cleared by soft-
ware.
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 logic 1, and is disabled by clearing this bit to logic 0.
Positive Hysteresis Voltage
(Programmed with CP0HYP Bits)
Negative Hysteresis Voltage
(Programmed by CP0HYN Bits)
VIN-
VIN+
INPUTS
CIRCUIT CONFIGU RATI ON
+
_
CP0+
CP0- CP0
VIN+
VIN- OUT
VOH
Positive Hysteresis
Disabled Maximum
Positive Hysteresis
Negative Hysteresis
Disabled Maximum
Negative Hysteresis
OUTPUT
VOL
C8051T600/1/2/3/4/5/6
61 Rev. 1.2
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 logic 0 a short time after the comparator is
enabled or its mode bits have been changed.
SFR Address = 0xF8; Bit-Addressable
SFR Definition 13.1. CPT0CN: Comparator0 Control
Bit76543210
Name CP0EN CP0OUT CP0RIF CP0FIF CP0HYP[1:0] CP0HYN[1:0]
Type R/W R R/W R/W R/W R/W
Reset 00000000
Bit Name Function
7 CP0EN Comp arator0 Enable Bit.
0: Comparator0 Disab led .
1: Comparator0 Enab led .
6CP0OUT
Comparator0 Output State Flag.
0: Voltage on CP0+ < CP0–.
1: Voltage on CP0+ > CP0–.
5CP0RIF
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.
4CP0FIF
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 = 5 mV.
10: Positive Hysteresis = 10 mV.
11: Positive Hysteresis = 20 mV.
1:0 CP0HYN[1:0] Comparator0 Negative Hysteresis Control Bits.
00: Negative Hysteresis Disabled.
01: Negative Hysteresis = 5 mV.
10: Negative Hysteresis = 10 mV.
11: Negative Hysteresis = 20 mV.
Rev. 1.2 62
C8051T600/1/2/3/4/5/6
SFR Address = 0x9D
SFR Definition 13.2. CPT0MD: Comparator0 Mode Selection
Bit76543210
Name CP0MD[1:0]
Type RRRRRR R/W
Reset 00000010
Bit Name Function
7:2 Unused Unused. Read = 000000b, 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 Consumption)
01: Mode 1
10: Mode 2
11: Mode 3 (Slowest Response Time, Lowest Power Consumption)
C8051T600/1/2/3/4/5/6
63 Rev. 1.2
13.1. Comparator Multiplexer
C8051T600/1/2/3/4/5/6 devices include an analog input multiplexer to connect Port I/O pins to the compar-
ator input s. The Comp arator0 input s are selected in the CPT0MX re gister (SFR Definition 13.3). The CMX-
0P1–CMX0P0 bits select the Comparator0 positive input; the CMX0N1–CMX0N0 bits select the
Comparator0 neg at ive inp u t.
Important Note About Comparator Inputs: The Port pins selected as comparator inputs should be con-
figured as analog inputs in their associated Port configur ation r egister, and configured to be skippe d by the
Crossbar (for details on Port configuration, see Section “22.5. Special Function Registers for Accessing
and Configuring Port I/O” on page 118).
Figure 13.3. Comparator Input Multiplexer Block Diagram
+
-
CP0 +
P0.0
CP0 -
CPT0MX
CMX0N0
CMX0N1
CMX0P1
CMX0P0
P0.2
P0.4
P0.6
P0.1
P0.3
P0.5
P0.7
GND
VDD
Rev. 1.2 64
C8051T600/1/2/3/4/5/6
SFR Address = 0x9F
SFR Definition 13.3. CPT0MX: Comparator0 MUX Selection
Bit76543210
Name CMX0N[1:0] CMX0P[1:0]
Type RR R/W RR R/W
Reset 00000000
Bit Name Function
7:6 Unused Unused. Read = 00b; Write = Don’t Care.
5:4 CMX0N[1:0] Comparator0 Negative Input MUX Selection.
00: P0.1
01: P0.3
10: P0.5
11: P0.7
3:2 Unused Unused. Read = 00b; Write = Don’t Care.
1:0 CMX0P[1:0] Comparator0 Positive Input MUX Selection.
00: P0.0 (Available only on packages with 8 I/O pins)
01: P0.2
10: P0.4
11: P0.6 (Available only on packages with 8 I/O pins)
C8051T600/1/2/3/4/5/6
65 Rev. 1.2
14. 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 deb ug hardware (see description in Section 27), and interfaces directly with the ana-
log and digit al subsystems providin g a complete dat a acquisitio n 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 Figure 14.1 for a block diagram).
The CIP-51 includes the following features:
Performance
The CIP-51 emplo ys a p ipeli ned architectu re tha t grea tly increases it s instr uction throug hput over the st an-
dard 8051 architecture. In a standard 8051, all instructions except for MUL and DIV take 12 or 24 syst em
clock cycles to execute, and usually have a maximum system clock of 12 MHz. 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.
Figure 14.1. CIP-51 Block Diagram
Fully Compatible with MCS-51 Instruction Set
25 MIPS Peak Throughput with 25 MHz Clock
0 to 25 MHz Clock Frequency
Extended Interrupt Handler
Reset Input
Power Management Modes
On-chip Debug Logic
Program and Data Memory Security
DATA BUS
TMP1 TMP2
PRGM. ADDRESS REG.
PC INCREMENTER
ALU
PSW
DATA BUS
DATA BUS
MEMORY
INTERFACE
MEM_ADDRESS
D8
PIPELINE
BUFFER
DATA POINTER
INTERRUPT
INTERFACE
SYSTEM_IRQs
EMULATION_IRQ
MEM_CONTROL
CONTROL
LOGIC
A16
PROGRAM COUNTER (PC)
STOP
CLOCK
RESET
IDLE POWER CONTROL
REGISTER
DATA BUS
SFR
BUS
INTERFACE
SFR_ADDRESS
SFR_CONTROL
SFR_WRITE_DATA
SFR_READ_DATA
D8
D8
B REGISTER
D8
D8
ACCUMULATOR
D8
D8
D8
D8
D8
D8
D8
D8
MEM_WRITE_DATA
MEM_READ_DATA
D8
SRAM
ADDRESS
REGISTER SRAM
D8
STACK POINTER
D8
Rev. 1.2 66
C8051T600/1/2/3/4/5/6
With the CIP-51's maximum system clock at 25 MHz, it has a peak throughput of 25 MIPS. The CIP-51 has
a total of 109 instructions. The table below shows the total number of instructions that require each execu-
tion time.
14.1. Instruction Set
The instruction set of the CIP-51 System Controller is fully compatible with the st and ard MCS-51 ™ instru c-
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.
14.1.1. 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. Table 14.1 is the
CIP-51 Instruction Set Summary, which includes the mnemonic, number of bytes, and number of clock
cycles for each instruction.
Clocks to Execute 1 22/333/444/55 8
Number of Instructions 26 50 5 14 7 3 1 2 1
C8051T600/1/2/3/4/5/6
67 Rev. 1.2
Table 14.1. 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
Rev. 1.2 68
C8051T600/1/2/3/4/5/6
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
Table 14.1. CIP-51 Instruction Set Summary (Continued)
Mnemonic Description Bytes Clock
Cycles
C8051T600/1/2/3/4/5/6
69 Rev. 1.2
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 2/3
JNC rel Jump if Carry is not set 2 2/3
JB bit, rel Jump if direct bit is set 3 3/4
JNB bit, rel Jump if direct bit is not set 3 3/4
JBC bit, rel Jump if direct bit is set and clear bit 3 3/4
Program Branching
ACALL addr11 Absolute subroutine call 2 3
LCALL addr16 Long subrou tin e ca ll 3 4
RET Return from subroutine 1 5
RETI Return from interrupt 1 5
AJMP addr11 Absolute jump 2 3
LJMP addr16 Long jump 3 4
SJMP rel Short jump (relative address) 2 3
JMP @A+DPTR Jump indirect relative to DPTR 1 3
JZ rel Jump if A equals zero 2 2/3
JNZ rel Jump if A does not equal zero 2 2/3
CJNE A, direct, rel Compare direct byte to A and jump if not equal 3 3/4
CJNE A, #data, rel Compare immediate to A and jump if not equal 3 3/4
CJNE Rn, #data, rel Compare immediate to Register and jump if not
equal 33/4
CJNE @Ri, #data, re l Compare immediate to indirect and jump if not
equal 34/5
DJNZ Rn, rel Decrement Register and jump if not zero 2 2/3
DJNZ direct, rel Decrement direct byte and jum p if not zero 3 3/4
NOP No operation 1 1
Table 14.1. CIP-51 Instruction Set Summary (Continued)
Mnemonic Description Bytes Clock
Cycles
Rev. 1.2 70
C8051T600/1/2/3/4/5/6
Notes on Registers, Oper ands 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 (twos complement) offset relative to the first byte of the following instruction. Us ed 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 b y ACALL and AJMP. The destination must b e within the same
2 kB page of program memory as the first byte of the following instruction.
addr16 - 16-bit d estination ad dress used b y LCALL and LJMP. The destination may be anywhere within
the 8 kB program memory space.
There is one unused opcode (0xA5) that performs the same function as NOP.
All mnemonics copyrighted © Intel Corporation 1980.
C8051T600/1/2/3/4/5/6
71 Rev. 1.2
14.2. 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 data sheet associated with their corresponding system function.
SFR Address = 0x82
SFR Address = 0x83
SFR Definition 14.1. DPL: Data Pointer Low Byte
Bit76543210
Name DPL[7:0]
Type R/W
Reset 00000000
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 14.2. DPH: Data Pointer High Byte
Bit76543210
Name DPH[7:0]
Type R/W
Reset 00000000
Bit Name Function
7:0 DPH[7:0] Data Pointer High.
The DPH register is the high byte of the 16-bit DPTR.
Rev. 1.2 72
C8051T600/1/2/3/4/5/6
SFR Address = 0x81
SFR Address = 0xE0; Bit-Addressable
SFR Address = 0xF0; Bit-Addressable
SFR Definition 14.3. SP: Stack Pointer
Bit76543210
Name SP[7:0]
Type R/W
Reset 00000111
Bit Name Function
7:0 SP[7:0] Stack Pointer.
The S t ack Pointer holds the location of the top of the stack. The st ack pointer is incre-
mented before every PUSH operation. The SP register defaults to 0x07 after reset.
SFR Definition 14.4. ACC: Accumulator
Bit76543210
Name ACC[7:0]
Type R/W
Reset 00000000
Bit Name Function
7:0 ACC[7:0] Accumulator.
This register is the accumulator for arithmetic operations.
SFR Definition 14.5. B: B Register
Bit76543210
Name B[7:0]
Type R/W
Reset 00000000
Bit Name Function
7:0 B[7:0] B Register.
This register serves as a second accumulator for certain arithmetic operations.
C8051T600/1/2/3/4/5/6
73 Rev. 1.2
SFR Address = 0xD0; Bit-Addressable
SFR Definition 14.6. PSW: Program Status Word
Bit76543210
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 00000000
Bit Name Function
7CY
Carry Flag.
This bit is set when the last arithmetic operation resulted in a carry (addition) or a bor-
row (subtraction). It is cleared to logic 0 by all other arithmetic operations.
6AC
Auxiliary Carry Flag.
This bit is set when the last arithmetic operation resulted in a carry into (addition) or a
borrow from (subtraction) th e high order nibble. It is cleared to logic 0 by all other arith-
metic opera tions .
5F0
User Flag 0.
This is a bit-addres sable, general purpose flag for use under software 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
2OV
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.
1F1
User Flag 1.
This is a bit-addres sable, general purpose flag for use under software control.
0PARITY
Parity Flag.
This bit is set to logic 1 if the sum of the eigh t bits in the accumulator is odd and cleared
if the sum is even.
C8051T600/1/2/3/4/5/6
74 Rev. 1.2
15. 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.
15.1. Program Memory
The CIP-51 core has a 64 kB program memory space. The C8051T600/1 implements 8192 bytes of this
program memory space as in-system, Byte-Programmable EPROM, organized in a contiguous block from
addresses 0x0000 to 0x1FFF. Note that 512 bytes (0x1E00 – 0x1FFF) of this memory are rese rved for fac-
tory use and are not available for user program storage. The C8051T602/3 implements 4096 bytes of
EPROM program memory space; the C8051T604/5 implements 2048 bytes of EPROM program memory
space, and the C8051T606 imple ment 1536 bytes of EPROM p rogram memo ry sp ace . C2 Register Defini-
tion 15.1 shows the program memory maps for C8051T600/1/2/3/4/5/6 devices.
Figure 15.1. Program Memory Map
Program memory is read-only from within firmware. Individual program memory bytes can be read using
the MOVC instruction. This facilitates the use of EPROM space for constant storage.
C8051T600/1
0x0000
Reserved
0x1DFF
7680 Bytes
EPROM Memory
0x1E00
0x0000
0x1000
Reserved
0x0FFF
4096 Bytes
EPROM Memory
0x1FFE
C8051T602/3 C8051T604/5
0x1FFF
Security Byte
0x1FFE
0x1FFF
Security Byte
0x0000
0x0800
Reserved
0x07FF
2048 Bytes
EPROM Memory
0x1FFE
0x1FFF
Security Byte
C8051T606
0x0000
Reserved
0x05FF
0x1FFF
Security Byte
0x0600
0x07FF
1536 Bytes
EPROM Memory
Rev. 1.2 75
C8051T600/1/2/3/4/5/6
15.2. Data Memory
The C8051T600/1/2/3/4/5 devices include 256 bytes of RAM, and the C8051T606 devices include 128
bytes of RAM. This memory is mapped into the internal data memory space of the 8051 controller core.
The RAM memory organi zation of the C8051T600/1/2/3/4/5/6 device family is shown in Figure 15.2
Figure 15.2. RAM Memory Map
15.2.1. Internal RAM
The 256 bytes of internal RAM on the C8051T600/1/2/3/4/5 are mapped into the data memory space from
0x00 through 0xFF. The 128 bytes of internal RAM on the C8051T606 are mapped into the data memory
space from 0x00 through 0x7F. The 128 bytes of data memory from 0x00 to 0x7F on all devices are used
for general purpose registers and scratch pad memory. Either direct or indirect addressing may be used to
access these 128 bytes 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 16 bytes, location s
0x20 through 0x2F, may either be addressed as bytes or as 128 bit locations accessible with the direct
addressing mode.
The upper 128 byte s of da ta memory available on the C8051 T60 0/1/2/3/4/5 ar e a ccessible on ly b y ind irect
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 128 bytes of data memory space
or the SFRs. Instructions that use direct addressing will access the SFR s pace. Instructions using indirect
addressing above 0x7F access the upper 128 bytes of data memory. Figure 15.2 illustrates the data mem-
ory organizatio n of the C8051T600/1/2/3/4/5/6.
(Direct and Indirect
Addressing)
0x00
0x7F
Upper 128 Bytes RAM
(Indirect Addressing)
‘T600/1/2/3/4/5 Only
0x80
0xFF Special Function
Registers
(Direct Addressing)
General Purpose
Registers
0x1F
0x20
0x2F Bit Addressable
Lower 128 Bytes RAM
(Direct and Indirect
Addressing)
0x30
C8051T600/1/2/3/4/5/6
76 Rev. 1.2
15.2.1.1. General Purpose Registers
The lower 32 bytes of dat a 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 th e progr am st atus wo rd , RS0 (PSW.3) and RS1
(PSW.4), select the active register bank (see description of the PSW in SFR Definition 14.6). This allows
fast context switching when entering subr outin es and interrupt se rvice routines. Indir ect addressin g modes
use registers R0 and R1 as index registers.
15.2.1.2. Bit Addressable Locations
In addition to direct access to d ata memory organized as bytes, the sixtee n data memory locations at 0x20
through 0x2F are also accessible as 128 individually addressable bits. Each bit has a bit address from
0x00 to 0x7F. Bit 0 of the byte at 0x20 ha s bit address 0x00 while bit 7 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.
15.2.1.3. Stack
A programmer's stack can be located anywhere in the internal data memory. The stack area is designated
using the S t ack 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 valu e pushed on the st ack is placed at location 0x08, which is also the first register (R0)
of register bank 1. T hus, if more th an one register bank is to be used, the SP should be initialized to a loca-
tion in the data memory not being used for data storage. The stack depth can extend up to the full RAM
area.
C8051T600/1/2/3/4/5/6
77 Rev. 1.2
16. 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 C8051T600/1/2/3/4/5/6's resources and
peripherals. The CIP- 51 controller core duplicates the SFRs found in a typical 8051 impl ement ation as well
as implementing additional SFRs used to configure and access the sub-systems unique to the
C8051T600/1/2/3/4/5/6. This allows the addition of new functionality while retaining compatibility with the
MCS-51™ instruction set. Table 16.1 lists the SFRs implemented in the C8051T600/1/2/3/4/5/6 device
family.
The SFR regist er s ar e a cce sse d any time th e dir ect 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
Table 16.2, for a detailed description of each register.
Table 16.1. Special Function Register (SFR) Memory Map
F8 CPT0CN PCA0L PCA0H PCA0CPL0 PCA0CPH0
F0 BP0MDIN EIP1
E8 ADC0CN PCA0CPL1 PCA0CPH1 PCA0CPL2 PCA0CPH2 RSTSRC
E0 ACC XBR0 XBR1 XBR2 IT01CF EIE1
D8 PCA0CN PCA0MD PCA0CPM0 PCA0CPM1 PCA0CPM2
D0 PSW REF0CN
C8 TMR2CN TMR2RLL TMR2RLH TMR2L TMR2H
C0 SMB0CN SMB0CF SMB0DAT ADC0GTL ADC0GTH ADC0LTL ADC0LTH REG0CN
B8 IP AMX0SL ADC0CF ADC0L ADC0H
B0 OSCXCN OSCICN OSCICL
A8 IE
A0 TOFFL TOFFH P0MDOUT
98 SCON0 SBUF0 CPT0MD CPT0MX
90
88 TCON TMOD TL0 TL1 TH0 TH1 CKCON
80 P0 SP DPL DPH PCON
0(8) 1(9) 2(A) 3(B) 4(C) 5(D) 6(E) 7(F)
(bit addressa ble )
Table 16.2. Sp ecial Function Registers
SFRs are listed in alphab et ica l or d er. All unde fined SFR loc ati on s are re se rve d
Register Address Description Page
ACC 0xE0 Accumulator 72
ADC0CF 0xBC ADC0 Configuration 44
ADC0CN 0xE8 ADC0 Control 46
ADC0GTH 0xC4 ADC0 Gr ea te r- Th a n Compare High 47
Rev. 1.2 78
C8051T600/1/2/3/4/5/6
ADC0GTL 0xC3 ADC0 Gr ea te r- Th a n Co mpare Lo w 47
ADC0H 0xBE ADC0 High 45
ADC0L 0xBD ADC0 Low 45
ADC0LTH 0xC6 ADC0 Less-Than Compare Word High 48
ADC0LTL 0xC5 ADC0 Less-Than Compare Word Low 48
AMX0SL 0xBB AMUX0 Multiplexer Channel Select 51
B0xF0 B Register 72
CKCON 0x8E Clock Control 146
CPT0CN 0xF8 Comparator0 Control 61
CPT0MD 0x9D Comparator0 Mode Selection 62
CPT0MX 0x9F Comparator0 MUX Selection 64
DPH 0x83 Data Pointer High 71
DPL 0x82 Data Pointer Low 71
EIE1 0xE6 Extended Interrupt Enable 1 85
EIP1 0xF6 Extended Interrupt Priority 1 86
IE 0xA8 Interrupt Enable 83
IP 0xB8 Interrupt Priority 84
IT01CF 0xE4 INT0/INT1 Configuration 88
OSCICL 0xB3 Internal Oscillator Calibration 101
OSCICN 0xB2 Internal Oscillator Control 102
OSCXCN 0xB1 External Oscillator Control 104
P0 0x80 Port 0 Latch 118
P0MDIN 0xF1 Port 0 In pu t Mo de Con fig ur at ion 119
P0MDOUT 0xA4 Port 0 Output Mode Configuration 119
PCA0CN 0xD8 PCA Control 173
PCA0CPH0 0xFC PCA Capt ur e 0 High 177
PCA0CPH1 0xEA PCA Captur e 1 Hi gh 177
PCA0CPH2 0xEC PCA Ca pt ur e 2 High 177
PCA0CPL0 0xFB PCA Capture 0 Lo w 177
PCA0CPL1 0xE9 PCA Capture 1 Low 1 77
PCA0CPL2 0xEB PCA Capture 2 Lo w 177
PCA0CPM0 0xDA PCA Module 0 Mode Register 175
PCA0CPM1 0xDB PCA Module 1 Mode Register 175
PCA0CPM2 0xDC PCA Module 2 Mode Register 175
Table 16.2. Special Function Registers (Continued)
SFRs are listed in alphab et ica l or d er. All unde fined SFR loc ati on s are re se rve d
Register Address Description Page
C8051T600/1/2/3/4/5/6
79 Rev. 1.2
PCA0H 0xFA PCA Counter High 176
PCA0L 0xF9 PCA Coun te r Lo w 176
PCA0MD 0xD9 PCA Mode 174
PCON 0x87 Power Control 91
PSW 0xD0 Program Status Word 73
REF0CN 0xD1 Voltage Reference Control 56
REG0CN 0xC7 Voltage Regulator Control 58
RSTSRC 0xEF Reset Source Configuration/Status 96
SBUF0 0x99 UART0 Data Buffer 143
SCON0 0x98 UART0 Control 142
SMB0CF 0xC1 SMBus Configuration 126
SMB0CN 0xC0 SMBus Control 128
SMB0DAT 0xC2 SMBus Data 130
SP 0x81 Stack Pointer 72
TCON 0x88 Timer/Counter Control 151
TH0 0x8C Timer/Counter 0 High 154
TH1 0x8D Timer/Counter 1 High 154
TL0 0x8A Timer/Counter 0 Low 153
TL1 0x8B Timer/Counter 1 Low 153
TMOD 0x89 Timer/Counter Mode 152
TMR2CN 0xC8 Timer/Counter 2 Control 157
TMR2H 0xCD Timer/Counter 2 High 159
TMR2L 0xCC Timer/Counter 2 Low 158
TMR2RLH 0xCB Timer/Counter 2 Reload High 158
TMR2RLL 0xCA Timer/Counter 2 Reload Low 158
TOFFH 0xA3 Temperature Sensor Offset Measurement High 54
TOFFL 0xA2 Temperature Sensor Offset Measurement Low 54
XBR0 0xE1 Port I/O Crossbar Control 0 115
XBR1 0xE2 Port I/O Crossbar Control 1 116
XBR2 0xE3 Port I/O Crossbar Control 2 117
All other SFR Locations Reserved
Table 16.2. Special Function Registers (Continued)
SFRs are listed in alphab et ica l or d er. All unde fined SFR loc ati on s are re se rve d
Register Address Description Page
C8051T600/1/2/3/4/5/6
80 Rev. 1.2
17. Interrupts
The C8051T600/1/2/3/4/5/6 includes an extended interrupt system supporting a total of 12 interrupt
sources with two priority levels. The allocation of interrupt sources between on-chip peripherals and exter-
nal input pins varies according to the specific version of the device. Each interrupt source has o ne or more
associated interrup t-pendin g flag(s) located in an SFR. When a per ipheral o r extern al source meet s a valid
interrupt condition, the associated interrupt-pending flag is set to logic 1.
If interrupt s are ena bled for the sour ce, an interrupt req uest is generated when the inter rupt-pending flag is
set. As soon as execution of the current instruction is complete, the CPU generates an LCALL to a pr ede-
termined address to begin executio n 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 requ est had not occurred. If inter rupt s are not enabled, the inter rupt-pending flag is ignored by the
hardware and program execution continues as normal. (The interrupt-pending flag is set to logic 1 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). However, interrupts must first be globally enabled by setting the EA bit
(IE.7) to logic 1 before the individual interrup t enabl es are recognize d. Setting the EA b it 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 imme di at el y 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 sour ce), 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-cy cle instruction, the interrupt will not be
taken.
Some interrupt-pending flags ar e auto matically cleare d by the hardware when the CPU vector s 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 81
C8051T600/1/2/3/4/5/6
17.1. MCU Interrupt Sources and Vectors
The C8051T600/1/2/3/4/5/6 MCUs support 12 interrupt sources. So f tware can simula te an i nterrupt b y set-
ting an interrupt-pending flag to logic 1. 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
Table 17.1. 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).
17.1.1. Interrupt Priorities
Each interrupt source can be in dividua lly prog ra mmed to one of two priority levels: low or high. A low prior-
ity interrupt service routine can be pree mpted by a high priority interrupt. A high priority interrupt cannot be
preempted. Each interrupt has an associated interrupt priority bit in an SFR (IP or EIP1) used to configure
its priority level. Low priority is the defa ult. If two interrupt s are recognize d simultane ously, the interrupt with
the higher priority is serviced first. If both interrupts have the same priority level, a fixed priority order is
used to arbitrate, given in Table 17.1.
17.1.2. Interrupt Latency
Interrupt response time depen ds on the state of the CPU when the interrupt occurs. Pending inter rupts are
sampled and priority decoded each system clock cycle. Therefore, the fastest possible response time is 5
system clock cycles: 1 clock cy cle to detect the interrupt and 4 clock 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 serv ice the pendin g inte rrup t. Th eref ore, the maxim um r espo nse tim e for an int errupt (when no
other interrupt is currently being serviced or the ne w 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
18 system clock cycles: 1 clock cycle to detect the interrupt, 5 clock cycles to execute the RETI, 8 clock
cycles to complete the DIV instruction and 4 clock 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.
C8051T600/1/2/3/4/5/6
82 Rev. 1.2
17.2. 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 fo r the peripheral and the beha vior of its interrupt-pending flag(s).
Table 17.1. Interrupt Summary
Interrupt Source Interrupt
Vector Priority
Order Pending Flag
Bit addressable?
Cleared by HW?
Enable
Flag Priority
Control
Reset 0x0000 Top None N/A N/A Always
Enabled Always
Highest
External Interrupt 0
(INT0)0x0003 0 IE0 (TCON.1) Y Y EX0 (IE.0) PX0 (IP.0)
Time r 0 Ove rf low 0x000B 1 TF0 (TCON.5) Y Y ET0 (IE. 1) PT0 (IP.1)
External Interrupt 1
(INT1)0x0013 2 IE1 (TCON.3) Y Y EX1 (IE.2) PX1 (IP.2)
Time r 1 Ove rf low 0x001B 3 TF1 (TCON.7) Y Y ET1 (IE. 3) PT1 (IP.3)
UART0 0x0023 4 RI0 (SCON0.0)
TI0 (SCON0.1) Y N ES0 (IE.4) PS0 (IP.4)
Timer 2 Overflow 0x002B 5 TF2H (TMR2CN.7)
TF2L (TM R2CN.6) Y N ET2 (IE.5) PT2 (IP.5)
SMB0 0x0033 6 SI (SMB0CN.0) Y N ESMB0
(EIE1.0) PSMB0
(EIP1.0)
ADC0
Window Compare 0x003B 7 AD0WINT (ADC0CN.3) Y N EWADC0
(EIE1.1) PWADC0
(EIP1.1)
ADC0
Conversion Complete 0x0043 8 AD0INT (ADC0CN.5) Y N EADC0
(EIE1.2) PADC0
(EIP1.2)
Programmable
Counter Array 0x004B 9 CF (PCA0CN.7)
CCFn (PCA0CN.n) Y N EPCA0
(EIE1.3) PPCA0
(EIP1.3)
Comparator0
Falling Edge 0x0053 10 CP0FIF (CPT0CN.4) N N ECP0
(EIE1.4) PCP0
(EIP1.4)
Comparator0
Rising Edge 0x005B 11 CP0RIF (CPT0CN.5) N N ECP0
(EIE1.5) PCP0
(EIP1.5)
Rev. 1.2 83
C8051T600/1/2/3/4/5/6
SFR Address = 0xA8; Bit-Addressable
SFR Definition 17.1. IE: Interrupt Enable
Bit76543210
Name EA IEGF0 ET2 ES0 ET1 EX1 ET0 EX0
Type R/W R/W R/W R/W R/W R/W R/W R/W
Reset 00000000
Bit Name Function
7EA
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.
6IEGF0
General Purpose Flag 0.
This is a general purpo se flag for use under software control.
5ET2
Enable Timer 2 Interrupt.
This bit set s the masking of the Timer 2 interrupt.
0: Disable Timer 2 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.
3ET1
Enable Timer 1 Interrupt.
This bit set s the masking of the Timer 1 interrupt.
0: Disable all Timer 1 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.
1ET0
Enable Timer 0 Interrupt.
This bit set s the masking of the Timer 0 interrupt.
0: Disable all Timer 0 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.
C8051T600/1/2/3/4/5/6
84 Rev. 1.2
SFR Address = 0xB8; Bit-Addressable
SFR Definition 17.2. IP: Interrupt Priority
Bit76543210
Name PT2 PS0 PT1 PX1 PT0 PX0
Type R R R/W R/W R/W R/W R/W R/W
Reset 11000000
Bit Name Function
7:6 Unused Unused. Read = 11b, Write = Don't Care.
5PT2
Timer 2 Interrupt Priority Control.
This bit sets the priority of th e Timer 2 interrupt.
0: Timer 2 interrupt set to low priority level.
1: Timer 2 interrupt set to high priority level.
4 PS0 UART0 Interrupt Priority Control.
This bit sets the priority of the UART0 interrupt.
0: UART0 interrupt set to low priority level.
1: UART0 interrupt se t to high priority level.
3PT1
Timer 1 Interrupt Priority Control.
This bit sets the priority of th e Timer 1 interrupt.
0: Timer 1 interrupt set to low priority level.
1: Timer 1 interrupt set to high priority level.
2 PX1 External Interrupt 1 Priority Control.
This bit sets the priority of the External Interrupt 1 interrupt.
0: External Interrupt 1 set to low priority level.
1: External Interrupt 1 set to high priority level.
1PT0
Timer 0 Interrupt Priority Control.
This bit sets the priority of th e Timer 0 interrupt.
0: Timer 0 interrupt set to low priority level.
1: Timer 0 interrupt set to high priority level.
0 PX0 External Interrupt 0 Priority Control.
This bit sets the priority of the External Interrupt 0 interrupt.
0: External Interrupt 0 set to low priority level.
1: External Interrupt 0 set to high priority level.
Rev. 1.2 85
C8051T600/1/2/3/4/5/6
SFR Address = 0xE6
SFR Definition 17.3. EIE1: Extended Interrupt Enable 1
Bit76543210
Name ECP0R ECP0F EPCA0 EADC0 EWADC0 ESMB0
Type R R R/W R/W R/W R/W R/W R/W
Reset 00000000
Bit Name Function
7:6 Unused Unused. Read = 00b; Write = Don’t Care.
5ECP0R
Enable Comparator0 (CP0) Rising Edge Interrupt.
This bit sets the masking of the CP0 rising edge interrupt.
0: Disable CP0 rising edge interrupts.
1: Enable interrupt requests generated by the CP0RIF flag.
4ECP0F
Enable Comparator0 (CP0) Falling Edge Interrupt.
This bit sets the masking of the CP0 falling edge interrupt.
0: Disable CP0 falling edge interrupts.
1: Enable interrupt requests generated by the CP0FIF flag.
3 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.
2 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.
1EWADC0
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).
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.
C8051T600/1/2/3/4/5/6
86 Rev. 1.2
SFR Address = 0xF6
SFR Definition 17.4. EIP1: Extended Interrupt Priority 1
Bit76543210
Name PCP0R PCP0F PPCA0 PADC0 PWADC0 PSMB0
Type R R R/W R/W R/W R/W R/W R/W
Reset 11000000
Bit Name Function
7:6 Unused Unused. Read = 11b; Write = Don’t Care.
5PCP0R
Comparator0 (CP0) Rising Edge Interrupt Priority Control.
This bit sets the priority of the CP0 rising edge interrupt.
0: CP0 rising edge interrupt set to low priority level.
1: CP0 rising edge interrupt set to high priority level.
4PCP0F
Comparator0 (CP0) Falling Edge Interrupt Priority Control.
This bit sets the priority of the CP0 falling edge interrupt.
0: CP0 falling edge interrupt set to low priority level.
1: CP0 falling edge interrupt set to high priority level.
3 PPCA0 Programmable Counter Array (PCA0) Interrupt Priority Control.
This bit sets the priority of the PCA0 interrupt.
0: PCA0 interrupt set to low priority level.
1: PCA0 interrupt set to high priority level.
2 PADC0 ADC0 Conversion Complete Interrupt Priority Control.
This bit sets the priority of the ADC0 Conversion Complete interrupt.
0: ADC0 Conversion Complete interrupt set to low priority level.
1: ADC0 Conversion Complete interrupt set to high priority level.
1PWADC0
ADC0 Window Comparator Interrupt Priority Control.
This bit sets the priority of the ADC0 Window interrupt.
0: ADC0 Window interrupt set to low priority level.
1: ADC0 Window interrupt set to high priority level.
0 PSMB0 SMBus (SMB0) Interrupt Priority Control.
This bit sets the priority of the SMB0 interrupt.
0: SMB0 interrupt set to low priority level.
1: SMB0 interrupt set to high priority level.
Rev. 1.2 87
C8051T600/1/2/3/4/5/6
17.3. INT0 and INT1 External Interrupt Sources
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 (INT 1 Polarity) bits in the IT01CF register select active high or
active low; the IT0 and IT1 bits in TCON (Section “25.1. Timer 0 and Timer 1” on page 147) select level or
edge sensitive. The table below lis ts the possible configurations.
INT0 and INT1 are assigned to Port pins as defined in the IT01CF register (see SFR Definition 17.5). Note
that INT0 and INT0 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 th e Crossbar to skip the selected pin(s).
This is accomplished by setting the associated bit in register XBR0 (see Section “22.3. Priority Crossbar
Decoder” on page 111 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 configu re d as edge-se nsitive , th e corres pondin g
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 w ill be
generated.
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
C8051T600/1/2/3/4/5/6
88 Rev. 1.2
SFR Address = 0xE4
SFR Definition 17.5. IT01CF: INT0/INT1 Configuration
Bit76543210
Name IN1PL IN1SL[2:0] IN0PL IN0SL[2:0]
Type R/W R/W R/W R/W
Reset 00000001
Bit Name Function
7IN1PL
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 disturb-
ing the peripheral that has been assigned the Port pin via the Crossbar. The Crossbar
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
3IN0PL
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 disturb-
ing the peripheral that has been assigned the Port pin via the Crossbar. The Crossbar
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
C8051T600/1/2/3/4/5/6
89 Rev. 1.2
18. Power Management Modes
The C8051T600/1/2/3/4/5/6 devices have two software programmable power management modes: idle
and stop. 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 oscilla-
tor is stopped (analog peripherals remain in their selected states; the external oscillator is not affected).
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 consumes the least
power because the ma jority of the device is shut d own with no clocks active. SFR Definition 18.1 describes
the Power Control Register (PCON) used to control the C8051T600/1/2/3/4/5/6's stop and idle power man-
agement modes.
Although the C8051T600/1/2/3/4/5/6 has idle and stop 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.
18.1. 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.
If the instruction following the write of the IDLE bit is a single -byte instruction and an interrupt occur s 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 “19.6. PCA Wa tchdog T i mer
Reset” on page 94 for more information on the use and configuration of the WDT.
Rev. 1.2 90
C8051T600/1/2/3/4/5/6
18.2. Stop Mode
Setting the St op Mode Select bit (PCON.1) causes the controller core to enter stop mode as soon as the
instruction that sets the bit completes execution. 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 REG0CN should be set to 1 prior to setting the STOP bit (see SFR Definition 12.1).
If the regulator is shut down using the STOPCF bit, only the RST pin or a full power cycle are capable of
resetting the device.
C8051T600/1/2/3/4/5/6
91 Rev. 1.2
SFR Address = 0x87
SFR Definition 18.1. PCON: Power Control
Bit76543210
Name GF[5:0] STOP IDLE
Type R/W R/W R/W
Reset 00000000
Bit Name Function
7:2 GF[5:0] General Purpose Flags 5–0.
These are general purpose flags for use under software control.
1STOP
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 os cillator stopped).
0IDLE
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.)
C8051T600/1/2/3/4/5/6
92 Rev. 1.2
19. Reset Sources
Reset circuitry allows the controller to be easily placed in a predefined default condition. On entry to this
reset state, the following occur:
CIP-51 halts program execution
Special Function Registers (SFRs) are initialized to their defined reset values
External Port pins are forced to a kn own 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 VDD Monitor and power-on resets, the RST pin is driven low until the device
exits the re set state.
On exit from the reset state, the program counter (PC) is reset, and the system clock defaults to the inter-
nal oscillator. The Wa tchdog Timer is enabled with the system clock divided by 12 as its clock source. Pro-
gram execution begins at location 0x0000.
Figure 19.1. Reset Sources
PCA
WDT
Missing
Clock
Detector
(one-
shot) (Software Reset)
System Reset
Reset
Funnel
Px.x
Px.x
EN SWRSF
Internal
Oscillator System
Clock CIP-51
Microcontroller
Core
Extended Interrupt
Handler
Clock Select
EN
WDT
Enable
MCD
Enable
EXTCLK External
Oscillator
Drive
Illegal
EPROM
Operation
RST
(wired-OR)
Power On
Reset
'0'
+
-
Comparator 0
C0RSEF
VDD
+
-
Supply
Monitor
Enable
Low
Frequency
Oscillator
Rev. 1.2 93
C8051T600/1/2/3/4/5/6
19.1. Power-On Reset
During power-up, the device is held in a reset state and the RST pin is driven low until VDD settles above
VRST. A delay occurs before the device is released from reset; the delay decreases as the VDD ramp time
increases (VDD ramp time is defined as how fast VDD ramps from 0 V to VRST). Figure 19.2. plots the
power-on and VDD monitor event timing. The maximum VDD ramp time is 1 ms; slower ramp times may
cause the device to be released from reset before VDD reaches the VRST level. For ramp times less than
1 ms, the power-on reset delay (TPORDelay) is typically less than 0.3 ms.
On exit from a power-on or VDD monitor reset, the PORSF flag (RSTSRC.1) is set by hardware to logic 1.
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 con-
tent of internal data memory should be assumed to be undefined after a power-on reset. The VDD monitor
is disabled following a power-on reset.
Figure 19.2. Power-On and VDD Monitor Reset Timing
Power-On
Reset
VDD
Monitor
Reset
RST
t
Supply Voltage
Logic HIGH
Logic LOW TPORDelay
VDD
VRST
VDD
C8051T600/1/2/3/4/5/6
94 Rev. 1.2
19.2. Power-Fail Reset/VDD Monitor
When a power-down transition or power irregularity causes VDD to drop below VRST, the power supply
monitor will drive the RST pin low and hold the CIP-51 in a re set stat e (see Figure 19.2). When VDD returns
to a level above VRST, the CIP-51 will be released from the reset state. Note that even though internal data
memory content s a re not altered by th e power-fail reset, it is impossible to determ ine if VDD dropped below
the level requir ed for data rete ntion. If the PORSF flag reads 1, the data may no longer be valid. The VDD
monitor is disabled after power-on resets. Its defined state (enabled/disabled) is not altered by any other
reset source. For example, if the VDD monitor is enabled by code and a software reset is performed, the
VDD monitor will still be enabled after the reset.
Important Note: If the VDD monitor is being turned on from a disabled state, it has the potential to gener-
ate a system reset. The VDD monitor is enabled and selected as a reset source by writing the PORSF flag
in RSTSRC to 1.
See Figure 19.2 for VDD monitor timing; note that the power-on-reset delay is not incurred after a VDD
monitor reset. See Table 8.4 for complete electrical characteristics of the VDD monitor.
19.3. 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 pi n genera tes a reset; a n externa l pullup a nd/or de coupling o f th e RST
pin may be necessary to avoid erroneous noise-induced resets. See Table 8.4 for complete RST pin spec-
ifications. The PINRSF flag (RSTSRC.0) is set on exit from an external reset.
19.4. Missing Clock Detector Reset
The Missing Clock Detector (MCD) is a one-shot circuit that is t riggered by the s yst em clock . If the syst em
clock remains high or low for more than the time specified in Section “8. Electrical Characteristics” on
page 30, the one-shot will time out and generate a reset. After a MCD reset, the MCDRSF flag
(RSTSRC.2) will read 1, signifying th e 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.
19.5. Comparator0 Reset
Comparator0 can be configured as a reset source by writing a 1 to the C0RSEF flag (RST SRC.5). Com-
parator0 should b e enabled and allowed to settle prior to writing to C0RSEF to prevent any turn-on chatter
on the output from gene rating 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.
19.6. PCA Watchdog Timer Reset
The watchdog timer (WDT) function of the pr ogrammab le counter ar ray (PCA) can be used to prevent so f t-
ware from running out of control during a system malfunction. The PCA WDT function can be enabled or
disabled by software as described in Section “26.4. Watchdog Timer Mode” on page 170; 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.
Rev. 1.2 95
C8051T600/1/2/3/4/5/6
19.7. EPROM Error Reset
If an EPROM read or write targets an illegal address, a system reset is generated. This may occur due to
any of the followi ng :
Programming hardware attempts to write or read an EPROM location which is above the user code
space address limit.
An EPROM read from firmware is attempted above user code space. This occurs when a MOVC
operation is attempted above the user code space add ress limit.
A Program read is attempted above user code space. This occurs when user code attempts to branch
to an address above the user code space address limit.
The MEMERR bit (RSTSRC.6) is set following an EPROM error reset. The state of the RST pin is unaf-
fected by this reset.
19.8. 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.
C8051T600/1/2/3/4/5/6
96 Rev. 1.2
SFR Address = 0xEF
SFR Definition 19.1. RSTSRC: Reset Source
Bit76543210
Name MEMERR 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
Bit Name Description Write Read
7 Unused Unused. Don’t care. 0
6 MEMERR EPROM Error Reset Flag. N/A Set to 1 if EPROM
read/write error caused
the last reset.
5 C0RSEF Comparator0 Reset Enable
and Flag. Writing a 1 enables
Comparator0 as a reset
source (active-low).
Set to 1 if Comparator0
caused the last reset.
4SWRSF
Software Reset Force and
Flag. Writing a 1 forces a sys-
tem reset. Set to 1 if last reset was
caused by a write to
SWRSF.
3 WDTRSF Watchdog Timer Reset Flag. N/A Set to 1 if W atchdog T imer
overflow caused the last
reset.
2 MCDRSF Missing Clock Detector
Enable and Flag. Writing a 1 enables the
Missing Clock Detector.
The MCD triggers a reset
if a missing clock condition
is detected.
Set to 1 if Missing Clock
Detector timeout caused
the last reset.
1PORSF
Power-On/VDD Monitor
Reset Flag, and VDD monitor
Reset Enable.
Writing a 1 enables the
VDD monitor and config-
ures it as a reset source.
Writing 1 to this bit while
the VDD monitor is dis-
abled may cause a sys-
tem reset.
Set to 1 any time a power-
on or VDD monitor reset
occurs.
When set to 1, all other
RSTSRC flags are inde-
terminate.
0PINRSF
HW Pin Reset Fl ag . N/A Set to 1 if RST pin caused
the last reset.
Note: Do not use read-modify-write operations on this register
C8051T600/1/2/3/4/5/6
97 Rev. 1.2
20. EPROM Memory
Electrically prog ra m mab l e r ead- o nly m e mo ry (EPRO M ) is included on-chip for program code stor age. The
EPROM memory can be programmed via the C2 debug and programming interface when a special pro-
gramming voltage is applied to the VPP pin. Each location in EPROM memory is programmable only once
(i.e., non-erasable). Table 8.6 on page 34 shows the EPROM specifications.
20.1. Programming and Reading the EPROM Memory
Reading and wr iting the EPROM memor y is accomplished thr ough the C2 progra mming and debu g inter-
face. When creating hardware to program the EPROM, it is necessary to follow the programming steps
listed below. Refer to the “C2 Interface Specification” available at http://www.silabs.com for details on com-
municating via the C2 interface. Section “27. C2 Interface” on page 178 has information about C2 register
addresses for the C8051T600/1/2/3/4/5/6.
20.1.1. EPROM Write Procedure
1. Reset the device using the RST pin.
2. Wait at least 20 µs before sending the first C2 command.
3. Place the device in core reset: Write 0x04 to the DEVCTL register.
4. Set the device to program mode (1st step): Write 0x40 to the EPCTL register.
5. Set the device to program mode (2nd step): Write 0x58 to the EPCTL register.
6. Apply the VPP programming Voltage.
7. Write the first EPROM address for programming to EPADDRH and EPADDRL.
8. Write a data byte to EPDAT. EPADDRH:L will increment by 1 after this write.
9. Use a C2 Address Read command to poll for write completion.
10.(Optional) Check the ERROR bit in register EPSTAT and abort the programmin g operation if ne cessary.
11.If programming is not finished, return to Step 8 to write the next address in sequence, or return to
Step 7 to program a new address.
12.Remove the VPP programming Voltage.
13.Remove program mode (1st step): Write 0x40 to the EPCTL register.
14.Remove program mode (2 nd step): Write 0x00 to the EPCTL register.
15.Reset the device: Write 0x02 and then 0x00 to the DEVCTL register.
Important No te: There is a finite amount of time which VPP can be applied without damaging the device,
which is cumu lative over the life of the de vice. Refer to Ta ble 8.1 on page 30 for the V PP timing specifica-
tion.
Rev. 1.2 98
C8051T600/1/2/3/4/5/6
20.1.2. EPROM Read Procedure
1. Reset the device using the RST pin.
2. Wait at least 20 µs before sending the first C2 command.
3. Place the device in core reset: Write 0x04 to the DEVCTL register.
4. Write 0x00 to the EPCTL register.
5. Write the first EPROM address for reading to EPADDRH and EPADDRL.
6. Read a data byte from EPDAT. EPADDRH:L will increment by 1 after this read.
7. (Optional) Check the ERROR bit in register EPSTAT and abort the memory read operation if necessary.
8. If reading is not finished, return to Step 6 to read the next address in sequence, or return to Step 5 to
select a new address.
9. Remove read mode (1st step): Write 0x40 to the EPCTL register.
10.Remove read mode (2nd step): Write 0x00 to the EPCTL register.
11.Reset the device: W rite 0x02 and then 0x00 to the DEVCTL register.
20.2. Security Options
The C8051T600/1/2/3/4/5/6 devices provide security options to prevent unauthorized viewing of propri-
etary program code and constants. A security byte in EPROM address space can be used to lock the pro-
gram memory from being rea d or written across the C2 interface. When read, the RDLOCK and WRLOCK
bits in register EPSTAT will indicate the lock status of the location currently addressed by EPADDR.
Table 20.1 shows the security byte decoding. See Section “15. Memory Organization” on page 74 for the
security byte location and EPROM memory map.
Important Note: Once the security byte has been written, there are no means of unlocking the
device. Locking memory from write access should be performed only after all other code has been
successfully programmed to memory.
Table 20.1. Security Byte Decoding
Bits Description
7–4 Write Lock: Clearing any of these bits to logic 0 prevents all code
memory from being written across the C2 interface.
3–0 Read Lock: Clearing any of these bits to logic 0 prevents all code
memory from being read across the C2 interface.
C8051T600/1/2/3/4/5/6
99 Rev. 1.2
20.3. Program Memory CRC
A CRC engine is included on-chip, which provides a means of verifying EPROM contents once the de vice
has been programmed. The CRC engine is available for EPROM verification even if the device is fully read
and write locked, allowing for verification of code contents at any time.
The CRC engine is operated th rough the C2 debu g and program ming inte rface, and pe rforms 16-bit CRCs
on individual 256-byte blocks of program memory, or a 32-bit CRC the entire memory space. To prevent
hacking and extrapolation of security-locked source code, the CRC engine will only allow CRCs to be per-
formed on contiguous 256-byte blocks beginning on 256-byte boundaries (lowest 8-bits of address are
0x00). For example, the CRC engine can perform a CRC for locations 0x0400 through 0x04FF, but it can-
not perform a CRC for locations 0x0401 through 0x0500, or on block sizes smaller or larger than
256 bytes.
20.3.1. Performing 32-bit CRCs on Full EPROM Content
A 32-bit CRC on the entire EPROM space is initiated by writing to the CRC1 byte over the C2 interface.
The CRC calculation begins at address 0x0000 and ends at the end of user EPROM space. The EPBusy
bit in register C2ADD will be set during the CRC operation, and cleared once the operation is complete.
The 32-bit results will be available in the CRC3-0 registers. CRC3 is the MSB, and CRC0 is the LSB. The
polynomial used for the 32-bit CRC calculation is 0x04C11DB7.
Note: If a 16-bit CRC has been performed since the last device reset, a device reset should be initiated
before performing a 32-bit CRC operation.
20.3.2. Performing 16-bit CRCs on 256- By te EPROM B lock s
A 16-bit CRC of individual 256- byte blocks of EPROM ca n be initiated by writing to the CRC0 byte over the
C2 interface. The value written to CRC0 is the high byte of the beginning address for the CRC. For exam-
ple, if CRC0 is written to 0x 02, the CRC will be perf ormed on the 256 bytes beginning at address 0x0200,
and ending at address 0x2FF. The EPBusy bit in register C2ADD will be set during the CRC operation, and
cleared once the operation is complete. The 16-bit results will be available in the CRC1-0 registers. CRC1
is the MSB, and CRC0 is the LSB. The polynom ial for the 16-bit CRC calculation is 0x1021
C8051T600/1/2/3/4/5/6
100 Rev. 1.2
21. Oscillators and Clock Selection
C8051T600/1/2/3/4/5/6 devices include a programmable internal high-frequency 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 Figure 21.1. The system clock can be sourced by the
external oscillator circuit or the internal osc illator (default). The internal oscillator offers a selectable post-
scaling feature, which is initially set to divide the clock by 8.
Figure 21.1. Oscillator Options
21.1. System Clock Selection
The CLKSL bit in register OSCICN selects which oscillator source is used as the system clock. CLKSL
must be set to 1 for the system clock to run from the external oscillator; however the external 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 the internal osc illator and external oscillator, as long as
the selected clock source is enabled and running.
The internal high-frequency oscillator requires 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.
OSC
Programmable
Internal Clock
Generator
Input
Circuit
EN
SYSCLK
n
OSCICL OSCICN
IFRDY
CLKSL
IOSCEN
IFCN1
IFCN0
EXTCLK
OSCXCN
XOSCMD2
XOSCMD1
XOSCMD0
XFCN2
XFCN1
XFCN0
CMOS Mode
EXTCLK
RC Mode
VDD
EXTCLK
C Mode
EXTCLK
C8051T600/1/2/3/4/5/6
101 Rev. 1.2
21.2. Programmable Internal High-Frequency (H-F) Oscillator
All C8051T600/1/2/3/4/5/6 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 21.1.
On C8051T600/1/2/3/4/5/6 devices, OSCICL is facto ry calibrated to obtain a 24.5 MHz base frequency.
The system clock may be derived from the programmed internal oscillator divided by 1, 2, 4, or 8, as
defined by the IFCN bits in register OSCICN. The divide value defaults to 8 following a reset.
SFR Address = 0xB3
SFR Definition 21.1. OSCICL: Internal H-F Oscillator Calibration
Bit76543210
Name OSCICL[6:0]
Type RR/W
Reset 0 Varies Varies Varies Varies Varies Varies Varies
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 slowest setting. The reset value is factory calibrated to generate an
internal oscillator frequency of 24.5 MHz.
Rev. 1.2 102
C8051T600/1/2/3/4/5/6
SFR Address = 0xB2
SFR Definition 21.2. OSCICN: Internal H-F Oscillator Control
Bit76543210
Name IFRDY CLKSL IOSCEN IFCN[1:0]
Type RRRRRR/W R/W
Reset 00010100
Bit Name Function
7:5 Unused Unused. Read = 000b; Write = Don’t Care
4IFRDY
Internal H-F Oscillator Frequency Ready Flag.
0: Internal H-F Oscillator is not running at programmed frequency.
1: Internal H-F Oscillator is running at programmed frequency.
3 CLKSL System Clock Source Select Bit.
0: SYSCLK derived from the Internal Oscillator, and scaled as per the IFCN bits.
1: SYSCLK derived from the External Clock circuit.
2IOSCEN
Internal H-F Oscillator Enable Bit.
0: Internal H-F Oscillator Disabled.
1: Internal H-F Oscillator Enabled.
1:0 IFCN[1:0] Internal H-F Oscillator Frequency Divider Control Bits.
00: SYSCLK derived from Internal H-F Oscillator divided by 8.
01: SYSCLK derived from Internal H-F Oscillator divided by 4.
10: SYSCLK derived from Internal H-F Oscillator divided by 2.
11: SYSCLK derived from Internal H-F Oscillator divided by 1.
C8051T600/1/2/3/4/5/6
103 Rev. 1.2
21.3. External Oscillator Drive Circuit
The external oscillator circuit may drive an external capacitor or RC network. A CMOS clock may also pro-
vide a clock input. In RC, capacitor, or CMOS clock configuration, the clock source should be wired to the
EXTCLK pin as shown in Figure 21.1. The type of external oscillator must be selected in the OSCXCN reg-
ister, and the frequency control bits (XFCN) must be selected appropriately (see SFR Definition 21.3).
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 capacitor, RC, or CMOS clock
mode, Port pin P0.3 is used as EXTCLK. The Port I/O Crossbar should be configured to skip the Port pin
used by the oscillator circuit; see Section “22.3. Priority Crossbar Decoder” on page 111 for Crossbar con-
figuration. Additionally, when using the external oscillator circuit in capacitor or RC mode, the associated
Port pin should be configured as an analog input. In CMOS clock mode, the associated pin should be
configured as a digital input. See Section “22.4. Port I/O Initialization” on page 114 for details on Port
input mode selection.
Rev. 1.2 104
C8051T600/1/2/3/4/5/6
SFR Address = 0xB1
SFR Definition 21.3. OSCXCN: External Oscillator Control
Bit76543210
Name XOSCMD[2:0] XFCN[2:0]
Type RR/WRR/W
Reset 00000000
Bit Name Function
7 Unused Read = 0b; Write = Don’t Care
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.
11x: Reserved.
3 Unused Read = 0b; Write = Don’t Care
2:0 XFCN[2:0] External Oscillator Frequency Control Bits.
Set according to the desired frequency range for RC mode.
Set according to the desired K Factor for C mo de.
XFCN RC Mode C Mode
000 f ≤ 25 kHz K Factor = 0.87
001 25 kHz < f ≤ 50 kHz K Factor = 2.6
010 50 kHz < f ≤ 100 kHz K Factor = 7.7
011 100 kHz < f ≤ 200 kHz K Factor = 22
100 200 kHz < f ≤ 400 kHz K Factor = 65
101 400 kHz < f ≤ 800 kHz K Factor = 180
110 800 kHz < f ≤ 1.6 MHz K Factor = 664
111 1.6 MHz < f ≤ 3.2 MHz K Factor = 1590
C8051T600/1/2/3/4/5/6
105 Rev. 1.2
21.3.1. External RC Example
If an RC network is used as an external oscillator source for the MCU, the circ uit should be configured as
shown in Figure 21.1, “RC Mode”. The capacitor should be no greater than 100 pF; 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 21.1,
where f = the frequency of oscillation in MHz, C = the capacitor value in pF, and R = the pull-up resistor
value in kΩ.
Equation 21.1. RC Mode Oscillator Frequency
For example: If the frequency desired is 100 kHz, let R = 246 kΩ and C = 50 pF:
f = 1.23( 103 ) / RC = 1.23 ( 103 ) / [ 246 x 50 ] = 0.1 MHz = 100 kHz
Referring to the table in SFR Definition 21.3, the required XFCN setting is 010b.
21.3.2. External Capacitor Example
If a capacitor is used as an external oscillator for the MCU, the circuit should be configured as shown in
Figure 21.1, “C Mode”. The capacitor should be no greater than 100 pF; however, for very small capaci-
tors, the tota l 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 ac cording to Equation 21.2, where f = the frequency of
oscillation in MHz, C = the capacitor value in pF, and VDD = the MCU power supply in Volts.
Equation 21.2. C Mode Oscillator Frequency
For example: Assume VDD = 3.0 V and f = 150 kHz:
f = KF / (C x VDD)
0.150 MHz = KF / (C x 3.0)
Since the frequency of roughly 150 kHz is d esired, select the K Factor from the tab le in SFR Definition 21.3
(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.
f1.23 103
×RC×()⁄=
fKF()RV
DD
×()⁄=
C8051T600/1/2/3/4/5/6
106 Rev. 1.2
22. Port Input/Output
Digital and analog resources are available through eight I/O pins on the C8051T600/1/2/3/4/5, or six I/O
pins on the C8051T606. Port pins P0.0-P0.7 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 Figure 22.1. Port pin
P0.7 is shared with the C2 Interface Data signal (C2D). The designer has complete control over which
functions are assigned, limited only by the number of physical I/O pins. This resource assignment flexibility
is achieved through the use of a Priori ty Crossbar Decod er. Note that the state o f a Port I/O p in can always
be read in the P0 port latch, re ga rd le ss of th e cro ss ba r set tin gs .
The crossbar assigns the selected internal digital resources to the I/O pin s based on the Prio rity Decoder
(Figure 22.3 and Figure 22.4). The registers XBR1 and XBR2, defined in SFR Definition 22.2 and SFR
Definition 22.3, are used to select internal digital functions.
All Port I/Os are 5 V tolerant (refer to Figure 22.2 for th e Po rt ce ll circ uit ). T h e Por t I/ O c ells ar e c on fig ur ed
as either push-pull or open-drain in the Port Output Mode registers (P0MDOUT). Complete Electrical
Specifications for Port I/O are given in Section “8. Electrical Characteristics” on page 30.
Figure 22.1. Port I/O Functional Block Diagram
XBR0, XBR1,
XBR2 Registers
Digital
Crossbar
Priority
Decoder
SYSCLK
2
2
(Internal Digital Signals)
Highest
Priority
Lowest
Priority
P0
I/O
Cells
P0.3
P0.4
8
P0MDOUT,
P0MDIN Registers
SMBus
UART
T0, T1 2
4
PCA
P0Port Latch (P0.0-P0.7)
8
CP0
Outputs 2
To Analog Peripherals
(ADC0, CP0, VREF, EXTCLK)
P0.5
P0.6
(‘T600/1/2/3/4/5 Only)
P0.7
P0.2
P0.1
P0.0
(‘T600/1/2/3/4/5 Only)
Rev. 1.2 107
C8051T600/1/2/3/4/5/6
22.1. Port I/O Modes of Operation
Port pins use the Port I/O cell shown in Figure 22.2. Each Port I/O cell can be configured by software for
analog I/O or digital I/O using the P0MDIN 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).
22.1.1. Port Pins Configured for Analog I/O
Any pins to be used as inputs to the comparator, ADC , external osc illator, or VREF should be c onfigured
for analog I/O (P0MDIN.n = 0). 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 inputs may still be used by analog peripherals; however, this practice is not recom-
mended and may result in measurement errors.
22.1.2. Port Pins Configured For Digital I/O
Any pins to be used by digital peripher als (UART, SMBus, PCA, etc.), external digital event captur e func-
tions, or as GPIO should be configu red as digit al I/O (P0MDIN.n = 1). For digit al I/O pins, one of two output
modes (push-pull or open-drain) must be selected using the P0MDOUT registers.
Push-pull outputs (P0MDOUT.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 driv er disabled; ther efore, they only
drive the Port pad to GND when the output logic value is 0 and become high impedance inputs (both high
and low drivers turned off) when the output logic value is 1.
When a digit a l I/O cell is placed in th e hi gh imped an ce 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 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 lo gic state to minimize power cons umption. Port pins configured for digital I/O always read back
the logic state of the Port pad, regardle ss of th e ou tp ut logic value of the Port pin.
Figure 22.2. Port I/O Cell Block Diagram
GND
VDD VDD
(WEAK)
PORT
PAD
To/From Analog
Peripheral
PxMDIN.x
(1 for digital)
(0 for analog)
Px.x – Output
Logic Value
(Port Latch or
Crossbar)
XBARE
(Crossbar
Enable)
Px.x – Input Logic Value
(Reads 0 when pin is configured as an analog I/O)
PxMDOUT.x
(1 for push-pull)
(0 for open-drain)
WEAKPUD
(Weak Pull-Up Disable)
C8051T600/1/2/3/4/5/6
108 Rev. 1.2
22.1.3. Interfacing Port I/O to 5V Logic
All Port I/O configured for digit al, open-drain o peration are cap able of interfacing to digit al logic operating at
a supply voltage higher than VDD and less than 5.25 V. An external pullup resistor to the higher supply
voltage is typically required for most systems.
Important Note: In a multi-voltage interface, the external pullup resistor shou ld be sized to allow a current
of at least 150 µA to flow into the Port pin when the supply voltage is between (VDD + 0.6 V) and (VDD +
1.0 V). Once the Port pin voltage increases beyond this range, the current flowing into the Port pin is mini-
mal.
Rev. 1.2 109
C8051T600/1/2/3/4/5/6
22.2. Assigning Port I/O Pins to Analog and Digital Functions
Port I/O pins can be assigned to various analog, digital, and external interrupt functions. The Port pins
assigned to analo g functions should be configur ed for ana log I/O, and Port pins assigned to digit al or exter-
nal interrupt functions should be configured for digital I/O.
22.2.1. Assigning Port I/O Pins to Analog Functions
Ta ble 22.1 shows all available analog functions that require Port I/O assignments. Port pins selected for
these analog functions should have their corresponding bit in XBR0 set to 1. This reserves the pin
for use by the analog function and does not allow it to be claimed by the crossbar. Table 22.1 shows the
potential mapping of Port I/O to each analog function.
22.2.2. 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 assignme nt; however, some digital functions bypass the cross-
bar in a manner similar to the analog functions listed above. Port pins used by these digital functions
and any Port pins selected for use as GPIO should have their corresponding bit in XBR0 set to 1.
Table 22.2 shows all available digital functions and the potential mapping of Port I/O to each digital func-
tion.
Table 22.1. Port I/O Assignment for Analog Functions
Analog Function Potentially Assignable
Port Pins SFR(s) used for
Assignment
ADC Input P0.0–P0.7 AMX0SL, XBR0
Comparator0 Inpu t P0.0–P0.7 C P T0 M X, X BR0
Voltage Reference Input for ADC (VREF) P0.0 REF0CN, XBR0
External Oscillator in RC or C Mode (EXTCLK) P0.3 OSCXCN, XBR0
Table 22.2. Port I/O Assignment for Digital Functions
Digital Function Potentially Assignable Port Pins SFR(s) used for
Assignment
UART0, SMBus, CP0,
CP0A, SYSCLK, PCA0
(CEX0-2 and ECI) , T0 or T1 .
Any Port pin available for assignment by the
crossbar. This includes P0.0 - P0.7 pins which
have their XBR0 bit set to 0.
Note: The crossbar will always assign UART0
pins to P0.4 and P0.5.
XBR1, XBR2
Any pin used for GPIO P0.0–P0.7 XBR0
C8051T600/1/2/3/4/5/6
110 Rev. 1.2
22.2.3. Assigning Port I/O Pins to External Digital Event Capture Functions
External digital event capture 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 digital event capture functions do not require
dedicated pins and will function on both GPIO pins (XBR0 = 1) and pins in use by the crossbar (XBR0 = 0).
External digital event capture functions cannot be used on pins configured for analog I/O. Table 22.3
shows all available external digital event capture functions.
Table 22.3. Port I/O Assignment for External Digital Event Capture Functions
Digital 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
Rev. 1.2 111
C8051T600/1/2/3/4/5/6
22.3. Priority Crossbar Decoder
The Priority Crossbar Decoder (Figure 22.3) 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 P0.4 and P0.5). 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 XBR0 register are set. The XBR0 register allows 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 XBR0 bit should be set. This applies to P0.0 if VREF is us ed, P0.3 if the exter-
nal oscillator circuit is enabled, P0.6 if the ADC 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. Figure 22.3 shows the potential pin assigments
available to t he crossbar periph erals. Figure 22. 4 and Figure 22.5 show two example crossbar configura-
tions, with and without skipping pins.
Figure 22.3. Priority Crossbar Decoder Potential Pin Assignments
TX0
RX0
SDA
SCL
CP0
CP0A
SYSCLK
CEX0
CEX1
CEX2
ECI
T0
T1
01234567
P0Port
Pin Number
Special
Function
Signals
VREF
EXTCLK
CNVSTR
0 0 0 0 0 0 0 x
XBR0
Pin Skip
Settings
All Port 0 pins are capable of being assigned to
crossbar peripherals.
The crossbar peripherals are assig ned in priority
order from top to bottom, according to this
diagram.
These boxes represent Port 0 pins which can
potentially be assigned to a peripheral.
Special Function Signals are not assigned by
the crossbar. When these signals are enabled,
the Crossbar should be manually configured to
skip the corresponding port pins.
Pins P0.0 through P0.6 can be “skipped” by
setting the corresponding bit in XBR0 to ‘1’.
C8051T600/1/2/3/4/5/6
112 Rev. 1.2
Figure 22.4. Priority Crossbar Decoder Example 1 - No Skipped Pins
TX0
RX0
SDA
SCL
CP0
CP0A
SYSCLK
CEX0
CEX1
CEX2
ECI
T0
T1
0 1 2 3 4 5 6 7
P0Port
Pin
Special
Function
Signals
VREF
EXTCLK
CNVSTR
0 0 0 0 0 0 0 x
XBR0
Pin Skip
Settings
In this example, the crossbar is configured to
assign the UART TX0 and RX0 signals, the
SMBus signals, and the SYSCLK signal. Note
that the SMBus signals are assigned as a pair,
and there are no pins skipped using the XBR0
register.
These boxes represent the port pin s wh ich
are used by the peripherals in th is configuration.
1st TX0 is assigned to P0.4
2nd RX0 is assigned to P0 .5
3rd SDA and SCL are assigned to P0.0 and P0.1,
respectively.
4th SYSCLK is assigned to P0.2
All unassigned pins can be used as GPIO or fo r
other non-crossbar function s.
Rev. 1.2 113
C8051T600/1/2/3/4/5/6
Figure 22.5. Priority Crossbar Decoder Example 2 - Skipping Pins
Registers XBR1 and XBR2 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). 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 func-
tions have been assigned.
TX0
RX0
SDA
SCL
CP0
CP0A
SYSCLK
CEX0
CEX1
CEX2
ECI
T0
T1
0 1 2 3 4 5 6 7
P0Port
Pin
Special
Function
Signals
VREF
EXTCLK
CNVSTR
1 0 0 1 0 0 0 x
XBR0
Pin Skip
Settings
P0.0 Skipped
P0.3 Skipped
In this example, the crossbar is configured to
assign the UART TX0 and RX0 signals, the
SMBus signals, and the SYSCLK signal. Note
that the SMBus signals are assigned as a pair.
Additionally, pins P0.0 and P0.3 are configured
to be skipped using the XBR0 register.
These boxes represent the port pins which
are used by the peripherals in this configuration.
1st TX0 is assigned to P0.4
2nd RX0 is assigned to P0.5
3rd SDA and SCL are assigned to P0.2 and P0.3,
respectively.
4th SYSCLK is assigned to P0.6
All unassigned pins, including those skipped by
XBR0 can be used as GPIO or for other non-
crossbar functions.
C8051T600/1/2/3/4/5/6
114 Rev. 1.2
22.4. 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 (P0MDIN).
2. Select the output mode (open-drain or push-pull) for all Port pins, using the Port Output Mode register
(P0MDOUT).
3. Select any pins to be skipped by the I/O crossbar using the XBR0 register.
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 conf igured as analog inputs. When a pin is configured as an analog input, its weak
pullup, digital driver, and digital receiver are disabled. This proc es s save s po we r an d re du ce s no ise on the
analog input. Pins configured as digital inputs may still be used by analog peripherals; however this prac-
tice is not recommended.
Additionally, all analog input pins should be configured to be skipped by the crossbar (accomplished by
setting the associated bits in XBR0). Port input mode is set in the P0MDIN register, where a 1 indicates a
digital inpu t, and a 0 indica tes an analog inpu t. All pins default to digit al inpu ts on reset. See SFR Definition
22.5 for the P0MDIN register details.
The output driver characteristics of the I/O pins are defined using the Port Output Mode register (P0MD-
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
P0MDOUT settings. When the WEAKPUD bit in XBR2 is 0, a weak pullup is enabled for all Port I/O config-
ured 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 XBR1 and XBR2 must be loaded with the appropriate values to select the digital I/O functions
required by the design. Setting the XBARE bit in XBR2 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. An alternative is to use the Configuration Wizard utility available on the Silicon Laboratories web site
to determine the Port I/O pin-assignments based on the XBRn Register settings.
The crossbar must be enab led to use Port pins as sta ndard Port I/O in output mo de. Port output drivers ar e
disabled while the crossbar is disabled.
Rev. 1.2 115
C8051T600/1/2/3/4/5/6
SFR Address = 0xE1
SFR Definition 22.1. XBR0: Port I/O Crossbar Register 0
Bit76543210
Name XSKP[6:0]
Type RR/W
Reset 00*000000*
Bit Name Function
7 Unused Unused. Read = 0; Write = Don’t Care.
6:0 XSKP[6:0] Crossbar Skip Enable Bits.
These bits select port 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.
Note: Bits 6 and 0 on the C8051T606 are read-only with a reset value of ‘1’.
C8051T600/1/2/3/4/5/6
116 Rev. 1.2
SFR Address = 0xE2
SFR Definition 22.2. XBR1: Port I/O Crossbar Register 1
Bit76543210
Name PCA0ME[1:0] CP0AE CP0E SYSCKE SMB0E URX0E UTX0E
Type R/W R/W R/W R/W R/W R/W R/W R/W
Reset 00000000
Bit Name Function
7:6 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.
5 CP0AE Comparator0 Asynchronous Output Enable.
0: Asynchronous CP0 unavailable at Port pin.
1: Asynchronous CP0 routed to Port pin.
4CP0E
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.
2SMB0E
SMBus I/O Enable.
0: SMBus I/O unavailab le at Po rt pin s.
1: SMBus I/O (SDA, SCL) routed to Port pins.
1URX0E
UART RX Input Enable.
0: UART RX unavailable at Port pin.
1: UART RX0 routed to Port pin P0.5.
0UTX0E
UART TX Output Enabl e.
0: UART TX0 unavailable at Port pin .
1: UART TX0 routed to Port pin P0.4.
Rev. 1.2 117
C8051T600/1/2/3/4/5/6
SFR Address = 0xE3
SFR Definition 22.3. XBR2: Port I/O Crossbar Register 2
Bit7 6543210
Name WEAKPUD XBARE T1E T0E ECIE
Type R/W R/W R R R R/W R/W R/W
Reset 0 0000000
Bit Name Function
7 WEAKPUD Port I/O Weak Pullup Disable.
0: Weak Pullups enabled (except for Ports whose I/O are configured for analog
mode).
1: Weak Pullups disabled.
6 XBARE Crossbar Enable.
0: Crossbar disabled.
1: Crossbar enabled.
5:3 Unused Unused. Read = 000b; Write = Don’t Care.
2T1E
T1 Enable.
0: T1 unavailable at Port pin.
1: T1 routed to Port pin.
1T0E
T0 Enable.
0: T0 unavailable at Port pin.
1: T0 routed to Port pin.
0ECIE
PCA0 External Counter Input Enable.
0: ECI unavailable at Port pin.
1: ECI routed to Port pin.
C8051T600/1/2/3/4/5/6
118 Rev. 1.2
22.5. Special Function Registers for Accessing and Configuring Port I/O
The Port I/O pins are accessed through the special function register P0, which is both byte addressable
and bit addressable. When writing to this SFR, the value written is latched to maintain 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 the Port 0 Latch register as the destination. The read-modify-write instructions
include ANL, ORL, XRL, JBC, CPL, INC, DEC, or DJNZ for any usage. However, when the destination is
an individual bit in P0 , the read-m odi fy- wr ite inst ru ct ions include MOV, CLR, or SETB. For all read-modify-
write instructions, the value of the latch register ( not the p in) is read , mod ified, and written back to the SFR.
The XBR0 register allows the individual Port pins to be assigned to digital functions or skipped by the
crossbar. All Port pins used for analog functions, GPIO, or dedicated digital functions should have their
XBR0 bit set to 1.
The Port input mode of the I/O pins is defined using the Port 0 Input Mode register (P0MDIN). 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 output driver characteristics of the I/O pins are defined using the Port 0 Output Mode register (P0MD-
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
P0MDOUT settings.
SFR Address = 0x80; Bit-Addressable
SFR Definition 22.4. P0: Port 0
Bit76543210
Name P0[7:0]
Type R/W
Reset 11111111
Bit Name Description Write Read
7:0 P0[7:0] Port 0 Data.
Sets the Port latch logic
value or reads the Port pin
logic state in Port cells con-
figured for digital I/O.
0: Set output latch to logic
LOW.
1: Set output latch to logic
HIGH.
0: P0.n Port pin is logic
LOW.
1: P0.n Port pin is logic
HIGH.
Note: Bits 6 and 0 on the C8051T606 are read-only.
Rev. 1.2 119
C8051T600/1/2/3/4/5/6
SFR Address = 0xF1
SFR Address = 0xA4
SFR Definition 22.5. P0MDIN: Port 0 Input Mode
Bit76543210
Name P0MDIN[7:0]
Type R/W
Reset 11111111
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 pullup, digital driver, and
digital receiver disable d.
0: Corresponding P0.n pin is configured for analog mode.
1: Correspon din g P0.n pin is not conf igu re d fo r an alo g mode .
Note: Bits 6 and 0 on the C8051T606 are read-only.
SFR Definition 22.6. P0MDOUT: Port 0 Output Mode
Bit76543210
Name P0MDOUT[7:0]
Type R/W
Reset 00000000
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: Correspon ding P0 .n Ou tp u t is push-p u ll.
Note: Bits 6 and 0 on the C8051T606 are read-only.
C8051T600/1/2/3/4/5/6
120 Rev. 1.2
23. SMBus
The SMBus I/O interface is a two-wire, bi-directional serial bus. The SM Bus is compliant wit h the System
Management Bus Specification, version 1.1, and compatible with the I2C serial bus. Reads and writes to
the interface by the system controller are byte oriented with the SMBus interface autonomously 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, dependin g 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 interface m ay opera te as a ma ster an d/or slav e, and may function on a bus with multiple mas-
ters. The SMBus provides control of SDA (serial data), SCL (serial clock) generation and synchronization,
arbitration logic, and START/STOP control and generation. A block diagram of the SMBus pe ripheral and
the associated SFRs is shown in Figure 23.1.
Figure 23.1. SMBus Block Diagram
Data Path
Control
SMBUS CONTROL LOGIC
C
R
O
S
S
B
A
R
SCL
FILTER
N
SDA
Control
SCL
Control
Interrupt
Request
Port I/O
SMB0CN
S
T
A
A
C
K
R
Q
A
R
B
L
O
S
T
A
C
K
S
I
T
X
M
O
D
E
M
A
S
T
E
R
S
T
O
01
00
10
11
T0 Overflow
T1 Overflow
TMR2H Overflow
TMR2L Overflow
SMB0CF
E
N
S
M
B
I
N
H
B
U
S
Y
E
X
T
H
O
L
D
S
M
B
T
O
E
S
M
B
F
T
E
S
M
B
C
S
1
S
M
B
C
S
0
01234567 SMB0DAT SDA
FILTER
N
Arbitration
SCL Synchronization
SCL Generation (Master Mode)
SDA Control
IRQ Generati on
Rev. 1.2 121
C8051T600/1/2/3/4/5/6
23.1. 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 Semiconduc tor.
3. System Management Bus Specification—Version 1.1, SBS Implementers Forum.
23.2. SMBus Configuration
Figure 23.2 shows a typical SMBus configuration. The SMBus specification allows any recessive voltage
between 3.0 V and 5.0 V; different devices on the bus may operate at d ifferent voltage levels. The b i-d ire c-
tional 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 th e bus is limited only by the re quirem ent that the r ise
and fall times on the bus not exceed 300 ns and 1000 ns, respectively.
Figure 23.2. Typical SMBus Configuration
23.3. 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. Note that it is not n ecessary to specify one
device as the Master in a system; any device that 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
Figure 23.3). 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 bi t (R/W) occupies the least-significan t bit position of th e address byte. The di rection bit is set
to logic 1 to indicate a "READ" operation and cleared to logic 0 to indicate a "WRITE" operation.
VDD = 5V
Master
Device Slave
Device 1 Slave
Device 2
VDD = 3V VDD = 5V VDD = 3V
SDA
SCL
C8051T600/1/2/3/4/5/6
122 Rev. 1.2
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
and wait s for an ACK fr om the slave a t the en d o f ea ch byte. Fo r READ opera tions, the slave tr ansm its the
data and waits 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 a nd free the bus. Figure 23.3 illustrates a
typical SMBus transaction.
Figure 23.3. SMBus Transaction
23.3.1. 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 bu s. A device is a “receiver” when an address or data byte is bein g 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 ph ase of the transfer, during which time the receiver controls the SDA line.
23.3.2. Arbitration
A master may star t a transfer on ly if the bus is free. The b us is free af ter a ST OP con dition or after the SCL
and SDA lines remain high for a spec ified time (see Section “23.3.5. SCL High (SMBus Free) Timeout” on
page 123). 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 interru ption; 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.
23.3.3. 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.
23.3.4. SCL Low Timeout
If the SCL line is held low b y a slave device on the bus, n o further communica tion is possible . Furthermore,
the master ca nnot for ce the SCL lin e high to co rrect th e 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
25 ms as a “timeout” condition. Devices that have detected the timeout condition must reset the communi-
cation no later than 10 ms after detecting the timeout condition.
SLA6
SDA SLA5-0 R/W D7 D6-0
SCL
Slave Address + R/W Data ByteSTART ACK NACK STOP
Rev. 1.2 123
C8051T600/1/2/3/4/5/6
When the S MBTOE bit in SM B0 CF is se t, Timer 3 is used to de tect SCL low tim e ou ts. Timer 3 is forced to
reload when SCL is high, and allowed to count when SCL is low. With Timer 3 enabled and configured to
overflow after 25 ms (and SMBTOE set), the T i mer 3 interrupt service routine ca n be used to reset ( disable
and re-enable) the SMBus in the event of an SCL low timeout.
23.3.5. SCL High (SMBus Free) Timeout
The SMBus specification stipulates that if the SCL and SDA lines remain hig h for more tha n 50 µs, the bus
is designated as free. When the SMBFTE bit in SMB0CF is set, the bus will be considered free if SCL and
SDA remain high for more than 10 SMBus 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.
23.4. Using the SMBus
The SMBus can oper ate in both Master and Slave modes. The interf ace 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
SMBus interrupts are generated for each data byte or slave address that is transferred. When a transmitter
(i.e., sending address/da ta, receiving an ACK), this interrupt is generated after the ACK cycle so that soft-
ware 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. See Section 23.5 for more details on transmission 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 SMB0CN (SMBus Control
register) to find the cause of the SMBus interrupt. The SMB0CN register is described in Section 23.4.2;
Table 23.4 provides a quick SMB0CN decoding reference.
23.4.1. SMBus Configuration Re gi st er
The SMBus Configuration register (SMB0CF) 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 tra ns fe r) .
C8051T600/1/2/3/4/5/6
124 Rev. 1.2
The SMBCS1–0 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 de fined in Equation 23.1. Note that the
selected clock source may be shared by other peripherals so long as the timer is left running at all times.
For example, Timer 1 overflows may generate the SMBus and UART baud rates simultaneously. Timer
configuration is covered in Section “25. Timers” on page 145.
Equation 23.1. Minimum SCL High and Low Times
The selected clock source should be configured to establish the minimum SCL High and Low times as per
Equation 23.1. 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 Equation 23.2.
Equation 23.2. Typical SMBus Bit Rate
Figure 23.4 shows the typical SCL generation described by Equation 23.2. Notice that THIGH is typically
twice as large as TLOW. The actual SCL output may vary due to other devices on the bus (SCL may be
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 23.1.
Figure 23.4. Typical SMBus SCL Generation
Setting the EXTHOLD bit ext ends the minimum setup and hold times for the SDA line. The minimum SDA
setup time defines the absolute minimum time th at SDA is stable before SCL transit ions from low-to-h igh.
The minimum SDA hold time defin es the absolute minimum time that the curre nt SDA value remains stabl e
Table 23.1. SMBus Clock Source Selection
SMBCS1 SMBCS0 SMBus Clock Source
0 0 Timer 0 Overflow
0 1 Timer 1 Overflow
1 0 Timer 2 High Byte Overflow
1 1 Timer 2 Low Byte Overflow
THighMin TLowMin 1
fClockSourceOverflow
----------------------------------------------
==
BitRate fClockSourceOverflow
3
----------------------------------------------
=
SCL
Timer Source
Overflows
SCL High TimeoutTLow THigh
Rev. 1.2 125
C8051T600/1/2/3/4/5/6
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 250 ns and 300 ns, respectively. Table 23.2 shows the min-
imum setup and hold times for the two EXTHOLD settings. Setup and hold time extensions are typically
necessary when SYSCLK is above 10 MHz.
With the SMBTOE bit set, Timer 3 should be configured to overflow after 25 ms in order to detect SCL low
timeouts (see Section “23.3.4. SC L Low Timeout” on page 122). The SMBus interface will force Timer 3 to
reload while SCL is hig h, and allow Timer 3 to count when SCL is low. The T imer 3 interrupt service routine
should be used to reset SMBus communication by disabling and re-enabling the SMBus.
SMBus Free T imeout detection can be enabled by setting the SMBFTE bit. When this bit is set, the bus will
be considered free if SDA and SCL remain high for more than 10 SMBus clock source periods (see
Figure 23.4).
Table 23.2. Minimum SDA Setup and Hold Times
EXTHOLD Minimum SDA Setup Time Minimum SDA Hold Time
0Tlow – 4 system clocks
or
1 system clock + s/w delay*3 system clocks
1 11 system clocks 12 system clocks
Note: Setup T ime 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.
C8051T600/1/2/3/4/5/6
126 Rev. 1.2
SFR Address = 0xC1
SFR Definition 23.1. SMB0CF: SMBus Clock/Configuration
Bit76543210
Name ENSMB INH BUSY EXTHOLD SMBTOE SMBFTE SMBCS[1:0]
Type R/W R/W R R/W R/W R/W R/W
Reset 00000000
Bit Name Function
7ENSMB
SMBus Enable.
This bit enables the SMBus interface when set to 1. When enabled, the interface
constantly monitors the SDA and SCL pins.
6INH
SMBus Slave Inhibit.
When this bit is set to logic 1, the SMBus does not gene rate an interrupt when slave
events occur. This effectively removes the SMBus slave from the bus. Master Mode
interrupts are not affecte d.
5BUSY
SMBus Busy Indicator.
This bit is set to logic 1 by hardware when a transfer is in progress. It is cleared to
logic 0 when a ST OP or free-timeout is sensed.
4 EXTHOLD SMBus Setup and Hold Time Extension Enable.
This bit controls the SDA setup and hold times according to Table 23.2.
0: SDA Extended Setup and Hold Times disabled.
1: SDA Extended Setup and Hold Times enabled.
3SMBTOE
SMBus SCL Timeout Detection Enable.
This bit enables SCL low timeout detection. If set to logic 1, the SMBus forces
T i mer 3 to reload wh ile SCL is high an d allows Timer 3 to count when SCL goes low.
If T ime r 3 is configured to Split Mode, only the High Byte of the timer is held in re load
while SCL is high. Timer 3 should be programmed to generate interrupts at 25 ms,
and the Timer 3 interrupt service routine should reset SMBus communication.
2SMBFTE
SMBus Free T imeout Detection Enable.
When this bit is set to logic 1, the bus will be considered free if SCL and SDA remain
high for more than 10 SMBus clock source periods.
1:0 SMBCS[1:0] SMBus Clock Source Selection.
These two bit s select th e SMBus clock sour ce, which is used to generate the SMBus
bit rate. The selected device should be configured according to Equation 23.1.
00: Timer 0 Overflow
01: Timer 1 Overflow
10: Timer 2 High Byte Overflow
11: Timer 2 Low Byte Overflow
Rev. 1.2 127
C8051T600/1/2/3/4/5/6
23.4.2. SMB0CN Control Regi st er
SMB0CN is used to control the interface and to provide status information (see SFR Definition 23.2). The
higher four bits of SMB0CN (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 gene ra te 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 be comes fr ee (STA is not c leared b y hardwa re 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.
As a receiver, writing the ACK bit defines the outgoing ACK value; as a transmitter, reading the ACK bit
indicates the value received on the last ACK c ycle. 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.
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 beginn ing and end of each transfe r, after each byte frame, or
when an arbitration is lost; see Table 23.3 for more details.
Import ant Note About t he 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.
Ta ble 23.3 lists all sources for hardware changes to the SMB0CN bits. Refer to Table 23.4 for SMBus sta-
tus decoding using the SMB0CN register.
C8051T600/1/2/3/4/5/6
128 Rev. 1.2
SFR Address = 0xC0; Bit-Addressable
SFR Definition 23.2. SMB0CN: SMBus Control
Bit76543210
Name MASTER TXMODE STA STO ACKRQ ARBLOST ACK SI
Type RRR/WR/WRRR/WR/W
Reset 00000000
Bit Name Description Read Write
7 MASTER SMBus Master/Slave
Indicator. This read-only bit
indicates when the SMBus is
operating as a master.
0: SMBus operating in
slave mode.
1: SMBus operating in
master mode.
N/A
6TXMODE
SMBus Transmit Mode
Indicator. This read-only bit
indicates when the SMBus is
operating as a tran smitter.
0: SMBus in Receiver
Mode.
1: SMBus in Transmitter
Mode.
N/A
5STA
SMBus Start Flag. 0: No Start or repeated
Start detected.
1: Start or repeated Start
detected.
0: No Start generated.
1: When Configured as a
Master, initiates a START
or repeated START.
4STO
SMBus Stop Flag. 0: No Stop condition
detected.
1: Stop condition detected
(if in Slave Mode) or pend-
ing (if in Master Mode).
0: No STOP condition is
transmitted.
1: When configured as a
Master, causes a STOP
condition to be transmit-
ted after the next ACK
cycle.
Cleared by Hardware.
3ACKRQ
SMBus Acknowledge
Request. 0: No Ack requested
1: ACK requested N/A
2ARBLOST
SMBus Arbitration Lost
Indicator. 0: No arbitration error.
1: Arbitration Lost N/A
1ACK
SMBus Acknowledge. 0: NACK received.
1: ACK received. 0: Send NACK
1: Send ACK
0SI
SMBus Interrupt Flag.
This bit is set by hardware
under the conditions listed in
Table 15.3. SI must be cleared
by software. While SI is set,
SCL is held low and the
SMBus is stalled.
0: No interrupt pending
1: Interrupt Pending 0: Clear interrupt, and initi-
ate next state machine
event.
1: Force interrupt.
Rev. 1.2 129
C8051T600/1/2/3/4/5/6
Table 23.3. Sources for Hardware Changes to SMB0CN
Bit Set by Hardware When: Cleared by Hardware When:
MASTER A START is generated. A STOP is ge nerated.
Arbitration is lost.
TXMODE
START is generated.
SMB0DAT is written before the start of an
SMBus frame.
A START is detected.
Arbitration is lost.
SMB0DAT is not written before the
start of an SMBus frame.
STA A START followed by an address byte is
received. Must be cleared by software.
STO
A STOP is detected while addressed as a
slave.
Arbitration is lost due to a detected STOP.
A pending STOP is generated.
ACKRQ A byte has been received and an ACK
response value is needed (only when
hardware ACK is not enabled).
After each ACK cycle.
ARBLOST
A repeated START is detected as a
MASTER when STA is low (unwanted
repeated START).
SCL is sensed low while attempting to
generate a STOP or repeated START
condition.
SDA is sensed low while transmitting a 1
(excluding ACK bits).
Each time SI is cleared.
ACK The incoming ACK value is low
(ACKNOWLEDGE). The incoming ACK value is high
(NOT ACKNOWLEDGE).
SI
A START has been generated.
Lost arbitration.
A byte has been transmitted and an
ACK/NACK received.
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.
Must be cleared by software.
C8051T600/1/2/3/4/5/6
130 Rev. 1.2
23.4.3. Data Register
The SMBus Data register SMB0DAT holds a byte of serial data to be transmitted or one that has just been
received. Software may safely read or write to the dat a register when th e SI flag is set. Sof tware sho uld not
attempt to ac cess the SMB0DAT register when the SM Bus is enable d and the SI flag is cleared to logic 0,
as the interface may be in the process of shifting a byte of data into or out of the register.
Data in SMB0DAT is always s hifted out MSB first. After a by te has been received, the first bit of received
data is located at the MSB of SMB0DAT. While data is being shifted out, data on the bus is simultaneously
being shifted in. SMB0DAT always contains the last data byte prese nt on the bu s. In th e even t of lost arb i-
tration, the transition from master transmitter to slave receiver is made with the correct data or address in
SMB0DAT.
SFR Address = 0xC2
SFR Definition 23.3. SMB0DAT: SMBus Data
Bit76543210
Name SMB0DAT[7:0]
Type R/W
Reset 00000000
Bit Name Function
7:0 SMB0DAT[7:0] SMBus Data.
The SMB0DAT register contain s a byte of data to be transmitted on the SMBus
serial interface or a byte th at has just been received on the SMBu s serial interface.
The CPU can read fr om or write to this re gister whenever the SI serial interrupt flag
(SMB0CN.0) is set to logic 1. The serial data in the register remains stable as long
as the SI flag is set. When the SI 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. 1.2 131
C8051T600/1/2/3/4/5/6
23.5. 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 a ny time a START is generated, an d rem ains i n
Master Mode until it loses an arbitration or generates a STOP. An SMBus interrupt is generated at the end
of all SMBus byte frames. As a receiver, the interrupt for an ACK occurs before the ACK. As a transmitter,
interrupts occur after the ACK.
23.5.1. 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 ad dress byt e, and a tra nsmitte r during all data bytes. The SMBu s interfac e 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 logic 0 (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. Note that the interface
will switch to Master Receiver Mode if SMB0DAT is not written following a Master Transmitter interrupt.
Figure 23.5 shows a typical master write sequence. Two transmit data bytes are shown, though any num-
ber of bytes may be transmitted. Notice that all of the “dat a byte transferred” interr upt s occur af ter the ACK
cycle in this mode.
Figure 23.5. Typical Master Write Sequence
A AAS W PData Byte Data ByteSLA
S = START
P = STOP
A = ACK
W = WRITE
SLA = Slave Address
Received by SMBus
Interface
Tran smitted by
SMBus Interface
Interrupt Locati ons
C8051T600/1/2/3/4/5/6
132 Rev. 1.2
23.5.2. 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 a ddress 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 logic 1 (READ). Serial data is then
received from the slave o n SDA while th e SMBus outp ut s the seria l clock. The sla ve transmit s one o r more
bytes of serial data.
The ACKRQ bit 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.
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. Figure 23.6 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
transferre d’ in te r ru pts occu r before the ACK.
Figure 23.6. Typical Master Read Sequence
Data ByteData Byte A NAS R PSLA
S = START
P = STOP
A = ACK
N = NACK
R = READ
SLA = Slave Address
Received by SMBus
Interface
Tran smitted by
SMBus Interface
Interrupt Locati ons
Rev. 1.2 133
C8051T600/1/2/3/4/5/6
23.5.3. Write Sequence (Slave)
During a write sequence, an SMBus master writes data to a slav e device. The slave in this transfer w ill 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 dire c-
tion bit (WRITE in this case) is received. 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 the received slave address is ignored by software (by NACKing the address), slave interrupts will be
inhibited until the next START is detected. If the received slave address is acknowledged, zero or more
data bytes are re ceived.
The ACKRQ bit 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.
The interface exits Slave Receiver Mode after receiving a ST OP. Note that the interface will switch to Slave
Transmitter Mode if SMB0DAT is written while an active Slave Receiver. Figure 23.7 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 tran sferred’ interrupts occur before the ACK.
Figure 23.7. Typical Slave Wr ite Sequence
PWSLASData ByteData Byte A AA
S = START
P = STOP
A = ACK
W = WRITE
SLA = Slave Address
Received by SMBus
Interface
Tran smitted by
SMBus Interface
Interrupt Locations
C8051T600/1/2/3/4/5/6
134 Rev. 1.2
23.5.4. 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 inter face 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. 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 the received slave address is ignored by software (by NACKing the address), slave interrupts will be
inhibited until the next START is detected. If the received slave address is acknowledged, zero or more
data bytes are transmitted. If the received slave address is acknowledged, data should be written to
SMB0DAT to be transmitted. 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 w ritten 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 ST OP. Note that the interface will switch to slave receiver mode if SMB0DAT is not written
following a S lave Transmitter interrupt. Figure 23.8 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.
Figure 23.8. Typical Slave Read Sequence
23.6. SMBus Status Decodin g
The current SMBus status can be easily decoded using the SMB0CN register. Table 23.4 describes the
typical actions t aken by firmware on each condition. In the t able, STATUS VECTOR refers to the fo ur upper
bits of SMB0CN: MASTER, TXMODE, STA, and STO. The shown response options are only the typical
responses; application-specific procedures are allowed as long as they conform to the SMBus specifica-
tion. Highlighted responses are allowed by hardware but do not conform to the SMBus specification.
PRSLASData ByteData Byte A NA
S = START
P = STOP
N = NACK
R = READ
SLA = Slave Address
Received by SMBus
Interface
Tran smitted by
SMBus Interface
Interrupt Locations
Rev. 1.2 135
C8051T600/1/2/3/4/5/6
Table 23.4. SMBus Status Decoding
Mode
Values Read
Current SMbus State Typical Response Options
Values to
Write
Next Status
Vector Expe ct ed
Status
Vector
ACKRQ
ARBLOST
ACK
STA
STO
ACK
Master Transmitter
1110 0 0 X A master START was gener-
ated. Load slave address + R/W into
SMB0DAT. 00X1100
1100
000
A master dat a or ad dress byte
was transmitted; NACK
received.
Set STA to restart transfer. 1 0 X 1110
Abort transfer. 01X —
001
A master dat a or ad dress byte
was transmitted; ACK
received.
Load next data byte into
SMB0DAT. 00X1100
End transfer with STOP. 0 1 X —
End transfer with STOP and start
another transfer. 11X —
Send repeated START. 1 0 X 1110
Switch to Master Receiver Mode
(clear SI without writing new data
to SMB0DAT).
0 0 X 1000
Master Receiver
1000 1 0 X A master data byte was
received; ACK requ ested.
Acknowledge received byte;
Read SMB0DAT. 0 0 1 1000
Send NACK to indicate last by te,
and send STOP. 010 —
Send NACK to indicate last by te,
and send STOP followed by
START.
1101110
Send ACK followed by repeated
START. 1011110
Send NACK to indicate last by te,
and send repeated START. 1001110
Send ACK and switch to Master
Transmitter Mode (write to
SMB0DAT before clearing SI).
0 0 1 1100
Send NACK and switch to Mas-
ter Transmitter Mode (write to
SMB0DAT before clearing SI).
0 0 0 1100
C8051T600/1/2/3/4/5/6
136 Rev. 1.2
Slave Transmitter
0100
000
A slave byte was transmitted;
NACK received. No action required (expecting
STOP condition). 0 0 X 0001
001
A slave byte was transmitted;
ACK rece ived. Load SMB0DAT with next data
byte to transmit. 0 0 X 0100
01X
A slave byte was transmitted;
error detected. No action required (expecting
Master to end transfer). 0 0 X 0001
0101 0 X X An illegal STOP or bus error
was detected while a Slave
Transmission was in progress. Clear STO. 00X —
Slave Receiver
0010
10X
A slave address + R/W was
received; ACK requ ested.
If Write, Acknowledge received
address 0 0 1 0000
If Read, Load SMB0DAT with
data byte; ACK re ceived addr ess 0 0 1 0100
NACK received address. 0 0 0 —
11X
Lost arbitra tio n as m ast er ;
slave address + R/W received;
ACK requested.
If Write, Acknowledge received
address 0 0 1 0000
If Read, Load SMB0DAT with
data byte; ACK re ceived addr ess 0 0 1 0100
NACK received address. 0 0 0 —
Reschedule failed transfer;
NACK received address. 1001110
0001 00X
A STOP was detected while
addres se d as a Slave Trans-
mitter or Slave Rec eiver. Clear STO. 00X —
11X
Lost arbitration while attempt-
ing a STOP. No action required (transfer
complete/aborted). 000 —
0000 1 0 X A slave byte was received;
ACK requested.
Acknowledge received byte;
Read SMB0DAT. 0 0 1 0000
NACK received byte. 0 0 0 —
Bus Error Condition
0010 0 1 X Lost arbitration while attempt-
ing a repeated START. Abort failed transfer. 0 0 X —
Reschedule failed transfer. 1 0 X 1110
0001 0 1 X Los t ar bit ra tio n du e to a
detected STOP. Abort failed transfer. 0 0 X —
Reschedule failed transfer. 1 0 X 1110
0000 1 1 X Lost arbitration while transmit-
ting a dat a byte as master. Abort failed transfer. 0 0 0 —
Reschedule failed transfer. 1001110
Table 23.4. SMBus Status Decoding
Mode
Values Read
Current SMbus State Typical Response Options
Values to
Write
Next Status
Vector Expected
Status
Vector
ACKRQ
ARBLOST
ACK
STA
STO
ACK
C8051T600/1/2/3/4/5/6
137 Rev. 1.2
24. UART0
UART0 is an asynchronous, full duplex serial port offering modes 1 and 3 of the standard 8051 UART.
Enhanced baud ra te su pport allows a wide r ange of clock sour ces to gene rate standard baud rates (details
in Section “24.1. Enhanced Baud Rate Generation” on page 138). 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 t he buffe red Receive regist er;
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 hardwa re when the CPU vectors to the in terrupt ser vice routine. They must be cle ared manually
by software, allowing software to determine the cause of the UART0 interrup t (transmit comp lete or receive
complete).
Figure 24.1. UART0 Block Diagram
UART Baud
Rate Generator
RI
SCON
RI
TI
RB8
TB8
REN
MCE
SMODE
Tx Control
Tx Clock Send
SBUF
(TX Shift)
Start
Data
Write to
SBUF
Crossbar
TX
Shift
Zero Detector
Tx IRQ
SET
QD
CLR
Stop Bit
TB8
SFR Bus
Serial
Port
Interrupt
TI Port I/O
Rx Control
Start
Rx Clock
Load
SBUF
Shift 0x1FF RB8
Rx IRQ
Input Shift Register
(9 bits)
Load SBUF
Read
SBUF
SFR Bus Crossbar
RX
SBUF
(RX Latch)
Rev. 1.2 138
C8051T600/1/2/3/4/5/6
24.1. Enhanced Baud Rate Generation
The UART0 baud rate is generated by Timer 1 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 Figure 24.2), 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 Timer 1 is enabled, and uses the same reload value (TH1). However, an
RX Timer 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 TX Timer state.
Figure 24.2. UART0 Baud Rate Logic
Timer 1 should be configured for Mode 2, 8-bit auto-reload (see Section “25.1.3. Mode 2: 8-bit
Counter/Timer with Auto-Reload” on page 149). The Timer 1 reload value should be set so that overflows
will occur at two times the desired UART baud rate frequency. Note that Timer 1 may be clocked by one of
six sources: SYSCLK, SYSCLK /4, SYSCLK/12, S YSCLK/48, the external oscillator clock/8, or an external
input T1. For any given Timer 1 clock source, the UART0 baud rate is determined by Equation 24.1-A and
Equation 24.1-B.
Equation 24.1. UART0 Baud Rate
Where T1CLK is the frequency of the clock supplied to Timer 1 and T1H is the high byte of Timer 1 (reload
value). Timer 1 clock frequency is selected as described in Section “25. Timers” on page 145. A quick ref-
erence for typical baud rates and system clock frequencies is given in Table 24.1 through Table 24.2. The
internal oscillator may still generate the system clock when the external oscillator is driving Timer 1.
RX Timer
Start
Detected
Overflow
Overflow
TH1
TL1 TX Clock
2
RX Clock
2
Timer 1 UART
UartBaudRate 1
2
---T1_Overflow_Rate×=
T1_Overflow_Rate T1CLK
256 TH1–
--------------------------
=
A)
B)
C8051T600/1/2/3/4/5/6
139 Rev. 1.2
24.2. 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 Figure 24.3.
Figure 24.3. UART Interconnect Diagram
24.2.1. 8-Bit UART
8-Bit UART mode uses a tot al of 10 bits per dat a byte: one st art bit, e ight dat a bit s (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 th e end of the transm ission (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 logic 1. 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 logic 0, and if MCE0 is logic 1, the stop bit must be logic 1. In the event of a receive data over-
run, the first received 8 bits are latched into the SBUF0 receive register and the following overrun data bits
are lost.
If these condition s ar e me t, 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.
Figure 24.4. 8-Bit UART Timing Diagram
OR
RS-232 C8051xxxx
RS-232
LEVEL
XLTR
TX
RX
C8051xxxx
RX
TX
MCU RX
TX
D1D0 D2 D3 D4 D5 D6 D7
START
BIT
MARK STOP
BIT
BIT TI MES
BIT SAMPLING
SPACE
Rev. 1.2 140
C8051T600/1/2/3/4/5/6
24.2.2. 9-Bit UART
The 9-bit UART mode uses a total of eleven bit s per dat a byte: a sta rt bit, 8 data bits (LSB first), a program-
mable 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 register 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 logic 0, an d (2) if MCE0 is logic 1, the 9th bit m ust be logic 1 (when MC E0 is logic 0 , 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.
Figure 24.5. 9-Bit UART Timing Diagram
D1D0 D2 D3 D4 D5 D6 D7
START
BIT
MARK STOP
BIT
BIT TIMES
BIT SAMPLING
SPACE D8
C8051T600/1/2/3/4/5/6
141 Rev. 1.2
24.3. Multiprocessor Communications
The 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 logic 1; in a data byte, the ninth bit is always set to logic 0.
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 logic 1 (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 ca n 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).
Figure 24.6. UART Multi-Processor Mode Interconnect Diagram
Master
Device Slave
Device
TXRX RX TX
Slave
Device
RX TX
Slave
Device
RX TX
V+
Rev. 1.2 142
C8051T600/1/2/3/4/5/6
SFR Address = 0x98; Bit-Addressable
SFR Definition 24.1. SCON0: Serial Port 0 Control
Bit76543210
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 01000000
Bit Name Function
7S0MODE
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.
5MCE0
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 level 1.
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 logic 1.
4REN0
Receive Enable.
0: UART0 reception disabled.
1: UART0 reception ena bled.
3TB80
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).
2RB80
Ninth Receive Bit.
RB80 is assigned the value of the STOP bit in Mode 0; it is assigned the value of the
9th data bit in Mode 1.
1TI0
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 in terrupt is enable d, setting this bit causes the CPU to vector to the UAR T0
interrupt se rvic e ro ut ine . This bit must be cleared manually by software.
0RI0
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.
C8051T600/1/2/3/4/5/6
143 Rev. 1.2
SFR Address = 0x99
SFR Definition 24.2. SBUF0: Serial (UART0) Port Data Buffer
Bit76543210
Name SBUF0[7:0]
Type R/W
Reset 00000000
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 a nd a receive latch reg ister .
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.
Rev. 1.2 144
C8051T600/1/2/3/4/5/6
Table 24.1. Timer Settings for Standard Baud Rates
Using The Internal 24.5 MHz Oscillator
Frequency: 24.5 MHz
Target
Baud Rate
(bps)
Baud Rate
% Error Oscillator
Divide
Factor
Timer Clock
Source SCA1–SCA0
(pre-scale
select)1
T1M1Timer 1
Reload
Value (hex)
SYSCLK from
Internal Osc.
230400 –0.32% 106 SYSCLK XX21 0xCB
115200 –0.32% 212 SYSCLK XX 1 0x96
57600 0.15% 426 SYSCLK XX 1 0x2B
28800 –0.32% 848 SYSCLK/4 01 0 0x96
14400 0.15% 1704 SYSCLK/12 00 0 0xB9
9600 –0.32% 2544 SYSCLK/12 00 0 0x96
2400 –0.32% 10176 SYSCLK/48 10 0 0x96
1200 0.15% 20448 SYSCLK/48 10 0 0x2B
Notes:
1. SCA1–SCA0 and T1M bit definitions can be found in Section 25.1.
2. X = Don’t care.
Table 24.2. Timer Settings for Standard Baud Rates
Using an External 22.1184 MHz Oscillator
Frequency: 22.1184 MHz
Target
Baud Rate
(bps)
Baud Rate
% Error Oscillator
Divide
Factor
Timer Clock
Source SCA1–SCA0
(pre-scale
select)1
T1M1Timer 1
Reload
Value (hex)
SYSCLK from
External Osc.
230400 0.00% 96 SYSCLK XX210xD0
115200 0.00% 192 SYSCLK XX 1 0xA0
57600 0.00% 384 SYSCLK XX 1 0x40
28800 0.00% 768 SYSCLK / 12 00 0 0xE0
14400 0.00% 1536 SYSCLK / 12 00 0 0xC0
9600 0.00% 2304 SYSCLK / 12 00 0 0xA0
2400 0.00% 9216 SYSCLK / 48 10 0 0xA0
1200 0.00% 18432 SYSCLK / 48 10 0 0x40
SYSCLK from
Internal Osc.
230400 0.00% 96 EXTCLK / 8 11 0 0xFA
115200 0.00% 192 EXTCLK / 8 11 0 0xF4
57600 0.00% 384 EXTCLK / 8 11 0 0xE8
28800 0.00% 768 EXTCLK / 8 11 0 0xD0
14400 0.00% 1536 EXTCLK / 8 11 0 0xA0
9600 0.00% 2304 EXTCLK / 8 11 0 0x70
Notes:
1. SCA1–SCA0 and T1M bit definitions can be found in Section 25.1.
2. X = Don’t care.
C8051T600/1/2/3/4/5/6
145 Rev. 1.2
25. Timers
Each MCU includes three counter/timers: two are 16-bit counter/timers compatible with those found in the
standard 8051, and one is a 16-bit auto-reload timer for use with the ADC, SMBus, or for general purpose
use. These timers can be used to measure time intervals, count external events, and generate periodic
interrupt requests. Timer 0 and Timer 1 are nearly identical and have four primary modes of operation.
Timer 2 offers 16-bit and split 8-bit timer functionality with auto-reload.
Timers 0 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
Timer 0 and/or Timer 1 may be clocked (see SFR Definition 25.1 for pre-sca led clock selection).
Timer 0/1 may then be configured to use this pre-scaled clock signal or the s ystem clock. Timer 2 may be
clocked by the system clock, the system clock divided by 12, or the external oscillator clock source divided
by 8.
Timer 0 and Timer 1 may also be operated as counters. When functioning as a counter, a counter/timer
register is incr emented on each hi gh-to-low tran sition at the sele cted input pin ( T0 or T1). Event s 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.
Timer 0 and Timer 1 Modes: Timer 2 Modes:
13-bit counter/timer 16 -b it tim er with au to -r elo a d
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)
Rev. 1.2 146
C8051T600/1/2/3/4/5/6
SFR Address = 0x8E
SFR Definition 25.1. CKCON: Clock Control
Bit76543210
Name T2MH T2ML T1M T0M SCA[1:0]
Type R R/W R/W R/W R/W R R/W
Reset 00000000
Bit Name Function
7 Unused Unused. Read = 0b, Write = Don’t Care
6T2MH
Timer 2 High Byte Clock Select.
Selects the clock supplied to the Timer 2 high byte (split 8-bit timer mode only).
0: Timer 2 high byte uses the clock defined by the T2XCLK bit in TMR2CN.
1: Timer 2 high byte uses the system clock.
5T2ML
Timer 2 Low Byte Clock Select.
Selects the clock supplied to Timer 2. If Timer 2 is configured in split 8-bit timer mode,
this bit selects the clock supplied to the lower 8-bit timer.
0: Timer 2 low byte uses the clock defined by the T2XCLK bit in TMR2CN.
1: Timer 2 low byte uses the system clock.
4T1M
Timer 1 Clock Select.
Selects the clo ck source supplied to Timer 1. Ignored when C/T1 is set to 1.
0: Timer 1 uses the clock defined by the prescale bits SCA[1:0].
1: Timer 1 uses the system clock.
3T0M
Timer 0 Clock Select.
Selects the clo ck source supplied to Timer 0. Ignored when C/T0 is set to 1.
0: Counter/Timer 0 uses the clock defined by the prescale bits SCA[1:0].
1: Counter/Timer 0 uses the system clock.
2 Unused Unused. Read = 0b, Write = Don’t Care
1:0 SCA[1:0] Timer 0/1 Prescale Bits.
These bits control the Timer 0/1 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)
C8051T600/1/2/3/4/5/6
147 Rev. 1.2
25.1. 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 Timer 0 and
Time r 1 as well as indica te status. Timer 0 interrupts can be enabled by se tting the ET0 bit in the IE regis-
ter (Section “17.2. Interrupt Re gister Descriptio ns” on page 82) ; Timer 1 interrup ts can be enabled by set -
ting the ET1 bit in the IE register (Section “17.2. Interrupt Register Descriptions” on page 82). 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 be low.
25.1.1. Mode 0: 13-bit Counter/Timer
Timer 0 and Timer 1 operate as 13-bit counter/timers in Mode 0. The following describes the configuration
and operation of Timer 0. However, both timers operate identically, and Timer 1 is configured in the same
manner as described for Timer 0.
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 shou ld 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 Timer 0 interrupts are
enabled.
The C/T0 bit in the TMOD register selects the counter/timer's clock source. When C/T0 is set to logic 1,
high-to-low transitions at the selected Timer 0 input pin (T0) increment the timer register (refer to Section
“22.3. Priority Crossbar Decoder” on page 111 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, Timer 0
is clocked by the system clock. When T0M is cleared, Timer 0 is clocked by the source selected by the
Clock Scale bits in CKCON (see SFR Definition 25.1).
Setting the TR0 bit (TCON.4) enables the timer when either GATE0 in the TMOD register is logic 0 or the
input signal INT0 is active as defined by bit IN0PL in register IT01CF (see SFR Definition 17.5). Setting
GATE0 to 1 allows the timer to be controlled by the external input signal INT0 (see Section “17.2. Interrupt
Register Descriptions” on page 82), facilitating pulse width measurements
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 reg ister for Timer 1 in the same manner as described ab ove for TL0 and TH0.
Timer 1 is configured and controlled using the relevant TCON and TMOD bits just as with Timer 0. The
input signal INT0 is used with Timer 1; the /INT1 polarity is defined by bit IN1PL in register IT01CF (see
SFR Definition 17.5).
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
Rev. 1.2 148
C8051T600/1/2/3/4/5/6
Figure 25.1. T0 Mode 0 Block Diagram
25.1.2. Mode 1: 16-bit Counter/Timer
Mode 1 operation is the same as Mode 0, except that the counter/timer registers use all 16 bits. The
counter/timers are enabled and configured in Mode 1 in the same manner as for Mode 0.
TCLK TL0
(5 bits) TH0
(8 bits)
TCON
TF0
TR0
TR1
TF1
IE1
IT1
IE0
IT0
Interrupt
TR0
0
1
0
1
SYSCLK
Pre-scaled Clock
TMOD
T
1
M
1
T
1
M
0
C
/
T
1
G
A
T
E
1
G
A
T
E
0
C
/
T
0
T
0
M
1
T
0
M
0
GATE0
INT0
T0
Crossbar
IT01CF
I
N
1
S
L
1
I
N
1
S
L
0
I
N
1
S
L
2
I
N
1
P
L
I
N
0
P
L
I
N
0
S
L
2
I
N
0
S
L
1
I
N
0
S
L
0
IN0PL XOR
T0M
C8051T600/1/2/3/4/5/6
149 Rev. 1.2
25.1.3. Mode 2: 8-bit Counter/Timer with Auto-Reload
Mode 2 configures T ime r 0 and T imer 1 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 Timer 0 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 Mode 2, Timer 1 operates identically to Timer 0.
Both counter/timers are enabled and configured in Mode 2 in the same manner as Mode 0. Setting the
TR0 bit (TC ON.4) e nables th e timer when either GATE0 in the TMOD register is logic 0 or when the input
signal INT0 is active as d efined by bit IN0PL in register IT01CF (see Se ction “17.3. INT0 and INT1 External
Interrupt Sources” on page 87 for details on th e external input signals INT0 and INT1).
Figure 25.2. T0 Mode 2 Block Diagram
TCLK
TMOD
T
1
M
1
T
1
M
0
C
/
T
1
G
A
T
E
1
G
A
T
E
0
C
/
T
0
T
0
M
1
T
0
M
0
TCON
TF0
TR0
TR1
TF1
IE1
IT1
IE0
IT0
Interrupt
TL0
(8 bits)
Reload
TH0
(8 bits)
0
1
0
1
SYSCLK
Pre-s caled Clock
IT01CF
I
N
1
S
L
1
I
N
1
S
L
0
I
N
1
S
L
2
I
N
1
P
L
I
N
0
P
L
I
N
0
S
L
2
I
N
0
S
L
1
I
N
0
S
L
0
TR0
GATE0
IN0PL XOR
INT0
T0
Crossbar
T0M
Rev. 1.2 150
C8051T600/1/2/3/4/5/6
25.1.4. Mode 3: Two 8-bit Counter/Timers (T imer 0 Only)
In Mode 3, Timer 0 is configured as two separate 8-bit counter/timers held in TL0 and TH0. The
counter/timer in TL0 is controlled using the Timer 0 control/status bits in TCON and TMOD: TR0, C/T0,
GATE0, and TF0. TL0 can use either the system clock or a n external input sig nal as it s timebase . The TH0
register is restricted to a timer function sourced by the system clock or prescaled clock. TH0 is enabled
using the Timer 1 run control bit TR1. TH0 sets the Timer 1 overflow flag TF1 on overflow and thus controls
the Timer 1 interrupt.
Timer 1 is inactive in Mode 3. When Timer 0 is operating in Mode 3, Timer 1 can be operated in Modes 0,
1, or 2, but cannot be clocked by external signals nor set the TF1 flag and generate an interrupt. However,
the Timer 1 overflow can be used to generate baud rates for the SMBus and/or UART, and/or initiate ADC
conversions. While Timer 0 is operating in Mode 3, Timer 1 run control is handled through its mode set-
tings. To run Timer 1 while Timer 0 is in Mode 3, set the Timer 1 Mode as 0, 1, or 2. To disable Timer 1,
configure it for Mode 3.
Figure 25.3. T0 Mode 3 Block Diagram
TL0
(8 bits)
TMOD
0
1
TCON
TF0
TR0
TR1
TF1
IE1
IT1
IE0
IT0
Interrupt
Interrupt
0
1
SYSCLK
Pre-scaled Clock TR1 TH0
(8 bits)
T
1
M
1
T
1
M
0
C
/
T
1
G
A
T
E
1
G
A
T
E
0
C
/
T
0
T
0
M
1
T
0
M
0
TR0
GATE0
IN0PL XOR
/INT0
T0
Crossbar
T0M
C8051T600/1/2/3/4/5/6
151 Rev. 1.2
SFR Address = 0x88; Bit-Addressable
SFR Definition 25.2. TCON: Timer Control
Bit76543210
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 00000000
Bit Name Function
7 TF1 Timer 1 Overflow Flag.
Set to 1 by ha rdware when Timer 1 overflows. This flag can be cleared by soft ware
but is automatically cleared when the CPU vectors to the Timer 1 interrupt service
routine.
6TR1
Timer 1 Run Control.
Timer 1 is enabled by setting this bit to 1.
5 TF0 Timer 0 Overflow Flag.
Set to 1 by ha rdware when Timer 0 overflows. This flag can be cleared by soft ware
but is automatically cleared when the CPU vectors to the Timer 0 interrupt service
routine.
4TR0
Timer 0 Run Control.
Timer 0 is enabled by setting this bit to 1.
3IE1
External Interru p t 1.
This flag is set by hardware when an edge/level of type defined by IT1 is detected. It
can be cleared by sof twa re but i s automa tically cleared when the CPU vectors to the
External Interrupt 1 service routine in edge-triggered mode.
2IT1
Interrupt 1 Type Select.
This bit selects whether the configured /INT1 interrupt will be edge or level sensitive.
/INT1 is configured active low or high by the IN1PL bit in the IT01CF register (see
SFR Definition 17.5).
0: /INT1 is level triggered.
1: /INT1 is edge triggered.
1IE0
External Interru p t 0.
This flag is set by hardware when an edge/level of type defined by IT1 is detected. It
can be cleared by sof twa re but i s automa tically cleared when the CPU vectors to the
External Interrupt 0 service routine in edge-triggered mode.
0IT0
Interrupt 0 Type Select.
This bit selects whether the configured INT0 interrupt will be edge or level sensitive.
INT0 is configured active low or high by the IN0PL bit in register IT01CF (see SFR
Definition 17.5).
0: INT0 is level triggered.
1: INT0 is edge triggered.
Rev. 1.2 152
C8051T600/1/2/3/4/5/6
SFR Address = 0x89
SFR Definition 25.3. TMOD: Timer Mode
Bit76543210
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 00000000
Bit Name Function
7GATE1
Timer 1 Gate Control.
0: Timer 1 enabled when TR1 = 1 irrespective of INT1 logic level.
1: Timer 1 enabled only when TR1 = 1 AND INT1 is active as de fined by bi t IN1PL in
register IT01CF (see SFR Definition 17.5).
6C/T1
Counter/Timer 1 Select.
0: Timer: Ti mer 1 incremented by clock defined by T1M bit in register CKCON.
1: Counter: Timer 1 incremented by high-to-low transitions on external pin (T1).
5:4 T1M[1:0] Timer 1 Mode Select.
These bits select the Timer 1 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-Re load
11: Mode 3, Timer 1 Inactive
3GATE0
Timer 0 Gate Control.
0: Timer 0 enabled when TR0 = 1 irrespective of INT0 logic level.
1: Timer 0 enabled only when TR0 = 1 AND INT0 is active as de fined by bi t IN0PL in
register IT01CF (see SFR Definition 17.5).
2C/T0
Counter/Timer 0 Select.
0: Timer: Ti mer 0 incremented by clock defined by T0M bit in register CKCON.
1: Counter: Timer 0 incremented by high-to-low transitions on external pin (T0).
1:0 T0M[1:0] Timer 0 Mode Select.
These bits select the Timer 0 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-Re load
11: Mode 3, Tw o 8- bit Coun te rs /Timers
C8051T600/1/2/3/4/5/6
153 Rev. 1.2
SFR Address = 0x8A
SFR Address = 0x8B
SFR Definition 25.4. TL0: Timer 0 Low Byte
Bit76543210
Name TL0[7:0]
Type R/W
Reset 00000000
Bit Name Function
7:0 TL0[7:0] Timer 0 Low Byte.
The TL0 register is the low byte of the 16-bit Timer 0.
SFR Definition 25.5. TL1: Timer 1 Low Byte
Bit76543210
Name TL1[7:0]
Type R/W
Reset 00000000
Bit Name Function
7:0 TL1[7:0] Timer 1 Low Byte.
The TL1 register is the low byte of the 16-bit Timer 1.
Rev. 1.2 154
C8051T600/1/2/3/4/5/6
SFR Address = 0x8C
SFR Address = 0x8D
SFR Definition 25.6. TH0: Timer 0 High Byte
Bit76543210
Name TH0[7:0]
Type R/W
Reset 00000000
Bit Name Function
7:0 TH0[7:0] Timer 0 High Byte.
The TH0 register is the high byte of the 16-bit Timer 0.
SFR Definition 25.7. TH1: Timer 1 High Byte
Bit76543210
Name TH1[7:0]
Type R/W
Reset 00000000
Bit Name Function
7:0 TH1[7:0] Timer 1 High Byte.
The TH1 register is the high byte of the 16-bit Timer 1.
C8051T600/1/2/3/4/5/6
155 Rev. 1.2
25.2. Timer 2
T imer 2 is a 16-bit timer formed by two 8-bit SFRs: TMR2L ( low byte) and T MR2H (high byte). Timer 2 may
operate in 16-bit auto-r eload mode or (split) 8-bit auto-reload mode. The T2SPLIT bit (TMR2CN.3) defines
the Timer 2 operation mode.
Timer 2 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 sy stem clock while Timer 2 (and/or the PCA) is clocked by an external preci-
sion oscillator. Note that the external oscillator source divided by eight is synchronized with the system
clock.
25.2.1. 16-bit Timer with Auto-Reload
When T2SPLIT (TMR2CN.3) is zero, Timer 2 operates as a 16-bit timer with auto-reload. Timer 2 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 2
reload registers (TMR2RLH and TMR2RLL) is loaded into the Timer 2 register as shown in Figure 25.4,
and the Timer 2 High Byte Overflow Flag (TMR2CN.7) is set. If Timer 2 interrupts ar e enable d, an interrupt
will be generated on each Timer 2 overflow. Additionally, if Timer 2 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 .
Figure 25.4. Timer 2 16-Bit Mode Block Diagram
External Clock / 8
SYSCLK / 12
SYSCLK
TMR2L TMR2H
TMR2RLL TMR2RLH Reload
TCLK
0
1
TR2
TMR2CN
T2SPLIT
TF2L
TF2H
T2XCLK
TR2
0
1
T2XCLK
Interrupt
TF2LEN
To ADC,
SMBus
To SMBus
TL2
Overflow
T2ML
Rev. 1.2 156
C8051T600/1/2/3/4/5/6
25.2.2. 8-bit Timers with Auto-Reload
When T2SPLIT is set, Timer 2 operates as two 8-bit timers (TMR2H and TMR2L). Both 8-bit timers oper-
ate in auto-reload mode as shown in Figure 25.5. 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 Timer 2 Clock Select bits (T2MH and T2ML in CKCON) select either SYSCLK or
the clock defined by the Timer 2 External Clock Select bit (T2XCLK in TMR2CN), as follows:
The TF2H bit is set when TMR2H overflows from 0xFF to 0x00; the TF2L bit is set when TMR2L overflows
from 0xFF to 0x0 0. When Timer 2 interrupts ar e enabled, a n interrupt is generate d each ti me TMR2H over-
flows. If Timer 2 interrupts are enabled and TF2LEN (TMR2CN.5) is set, an interrupt is generated 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 Timer 2 interrupt. The TF2H and TF2L interrupt flags are not
cleared by hardware and must be manually cleared by software.
Figure 25.5. Timer 2 8-Bit Mode Block Diagram
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
SYSCLK
TCLK
0
1TR2
External Cl ock / 8
SYSCLK / 12 0
1
T2XCLK
1
0
TMR2H
TMR2RLH Reload
Reload
TCLK TMR2L
TMR2RLL
Interrupt
TMR2CN
T2SPLIT
TF2LEN
TF2L
TF2H
T2XCLK
TR2
To ADC,
SMBus
To SMBus
T2ML
T2MH
C8051T600/1/2/3/4/5/6
157 Rev. 1.2
SFR Address = 0xC8; Bit-Addressable
SFR Definition 25.8. TMR2CN: Timer 2 Control
Bit76543210
Name TF2H TF2L TF2LEN T2SPLIT TR2 T2XCLK
Type R/W R/W R/W R/W R/W R/W R R/W
Reset 00000000
Bit Name Function
7 TF2H Timer 2 High Byte Overflow Flag.
Set by hardware whe n the Timer 2 high byte overflow s fro m 0x FF to 0x00. In 16 bit
mode, this will occur when Timer 2 overflows from 0xFFFF to 0x0000. When the
Time r 2 inter rupt is enab le d, settin g this bit ca us es th e CPU to vecto r to the Timer 2
interrupt service routine. This bit is not au to m at ically cleared by hardware .
6 TF2L Timer 2 Low Byte Overflow Flag.
Set by hardware when the Timer 2 low byte overflows from 0xFF to 0x00. TF2L will
be set when the low byte overflows regardless of the Timer 2 mode. This bit is not
automatically cleared by hardware.
5 TF2LEN Timer 2 Low Byte Interrupt Enable.
When set to 1, this bit enables Timer 2 low byte interrupts. If Timer 2 interrupts are
also enabled, an interrupt will be generated when the low byte of Timer 2 overflows.
4 Unused Unused. Read = 0b; Write = Don’t Care
3 T2SPLIT Timer 2 Split Mode Enable.
When this bit is set, Timer 2 operates as two 8-bit timers with auto-reload.
0: Timer 2 operates in 16-bit auto-reload mode.
1: Timer 2 operates as two 8-bit auto-reload timers.
2TR2
Timer 2 Run Control.
Timer 2 is enabled by setting this bit to 1. In 8-bit mode, this bit enables/disables
TMR2H only; TMR2L is always enabled in split mod e .
1 Unused Unused. Read = 0b; Write = Don’t Care
0T2XCLK
Timer 2 External Clock Select.
This bit selects the external clock source for Timer 2. If Timer 2 is in 8-bit mode, this
bit selects the external oscillator clock source for both timer bytes. However, the
Timer 2 Clock Select bits (T2MH and T2ML in register CKCON) may still be used to
select between the external clock and the system clock for eithe r timer.
0: Timer 2 clock is the system clock divided by 12.
1: Timer 2 clock is the external clock divided by 8 (synchronized with SYSCLK).
Rev. 1.2 158
C8051T600/1/2/3/4/5/6
SFR Address = 0xCA
SFR Address = 0xCB
SFR Address = 0xCC
SFR Definition 25.9. TMR2RLL: Timer 2 Reload Register Low Byte
Bit76543210
Name TMR2RLL[7:0]
Type R/W
Reset 00000000
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 25.10. TMR2RLH: Timer 2 Reload Register High Byte
Bit76543210
Name TMR2RLH[7:0]
Type R/W
Reset 00000000
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 25.11. TMR2L: Timer 2 Low Byte
Bit76543210
Name TMR2L[7:0]
Type R/W
Reset 00000000
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.
C8051T600/1/2/3/4/5/6
159 Rev. 1.2
SFR Address = 0xCD
SFR Definition 25.12. TMR2H Timer 2 High Byte
Bit76543210
Name TMR2H[7:0]
Type R/W
Reset 00000000
Bit Name Function
7:0 TMR2H[7:0] Timer 2 Low Byte.
In 16-bit mode, the TM R 2H re gis te r con tains the hig h by te of the 16- bit Timer 2. In 8-
bit mode, TMR2H contains the 8-bit high byte timer value.
C8051T600/1/2/3/4/5/6
160 Rev. 1.2
26. 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 time base that can select between six sources: system clock, system clock divided by four,
system clock divided by twelve, the external oscillator clock source divided by eight, Timer 0 overflows, or
an external clock signal on the ECI input pin. Each Capture/Compare module may be configured to oper-
ate independently in one of six modes: Edge-Triggered Capture, Software Timer, High-Speed Output, Fre-
quency Output, 8-Bit PWM, or 16-Bit PWM (each mode is described in Section “26.3. Capture/Compare
Modules” on page 163). The external oscillator clock option is ideal for real-time clock (RTC) functionality,
allowing the PCA to be clocked by a precision external oscillat or while the internal oscillator drives the sys-
tem clock. The PCA is configured and controlled through the system controller's Special Function Regis-
ters. The PCA block diagra m is shown in Figure 26.1
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 26.4 for details.
Figure 26.1. PCA Block Diagram
Capture/Compare
Module 1
Capture/Compare
Module 0 Capture/Compare
Module 2 / WDT
CEX1
ECI
Crossbar
CEX2
CEX0
Port I/O
16-Bit Counter/Timer
PCA
CLOCK
MUX
SYSCLK/12
SYSCLK/4
Timer 0 Overflow
ECI
SYSCLK
External Clock/8
Rev. 1.2 161
C8051T600/1/2/3/4/5/6
26.1. 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 regi ster 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 Table 26.1.
When the counter/timer overflows from 0xFFFF to 0x0000, the Counter Overflow Flag (CF) in PCA0MD is
set to logic 1 and an interrupt request is generated if CF interrupts are enabled. Setting the ECF bit in
PCA0MD to logic 1 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.
Figure 26.2. PCA Counter/Timer Block Diagram
Tab le 26.1. PCA Timebase Input Options
CPS2 CPS1 CPS0 Timebase
0 0 0 System clock div i ded by 12
0 0 1 System clock div i ded by 4
0 1 0 Timer 0 overflow
011
High-to-low transitions on ECI (max rate = system clock divided
by 4)
1 0 0 System clock
1 0 1 External oscillator source divided by 8*
1 1 x Reserved
Note: External oscillator source divided by 8 is synchronized with the system clock.
PCA0CN
C
FC
RC
C
F
0
C
C
F
2
C
C
F
1
PCA0MD
C
I
D
L
W
D
T
E
E
C
F
C
P
S
1
C
P
S
0
W
D
L
C
K
C
P
S
2
IDLE
0
1PCA0H PCA0L
Snapshot
Register
To SFR Bus
Overflow To PCA Interrupt System
CF
PCA0L
read
To PCA Modules
SYSCLK/12
SYSCLK/4
Timer 0 Overflow
ECI
000
001
010
011
100
101
SYSCLK
External Clock/8
C8051T600/1/2/3/4/5/6
162 Rev. 1.2
26.2. PCA0 Interrupt Sources
Figure 26.3 shows a diagr am of the PCA inter ru pt tree. The re ar e fou r indep end ent e v ent flags tha t can b e
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, 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 and ECCFn for each CCFn). PCA0
interrupts must be globally enabled before any individual interrupt sources are recognized by the proces-
sor. PCA0 interrupts are globally enabled by setting the EA bit and the EPCA0 bit to logic 1.
Figure 26.3. PCA Interrupt Block Diagram
PCA0CN
C
FC
RC
C
F
0
C
C
F
2
C
C
F
1
PCA0MD
C
I
D
L
W
D
T
E
E
C
F
C
P
S
1
C
P
S
0
W
D
L
C
K
C
P
S
2
0
1
PCA Module 0
(CCF0)
PCA Module 1
(CCF1)
ECCF1
0
1
ECCF0
0
1
PCA Module 2
(CCF2)
ECCF2
PCA Counter/Timer 16-
bit Overflow 0
1
Interrupt
Priority
Decoder
EPCA0
0
1
EA
0
1
PCA0CPMn
(for n = 0 to 2)
P
W
M
1
6
n
E
C
O
M
n
E
C
C
F
n
T
O
G
n
P
W
M
n
C
A
P
P
n
C
A
P
N
n
M
A
T
n
Rev. 1.2 163
C8051T600/1/2/3/4/5/6
26.3. 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-bit pulse width modulator, or 16-bit pulse
width modulator. Each module has Special Function Registers (SFRs) associated with it in the CIP-51 sys-
tem controller. These registers are used to exchange dat a with a module and config ure the mo dule's mod e
of operation. Table 26.2 summarizes the bit settings in the PCA0CPMn register used to select the PCA
capture/compare module’s operating mode. Setting the ECCFn bit in a PCA0CPMn register enables the
module's CCFn inte rrupt.
Table 26.2. PCA0CPM Bit Settings for PCA Capture/Compare Modules
Operational Mode PCA0CPMn
Bit Number76543210
Capture triggered by positive edge on CEXn XX10000A
Capture triggered by negative edge on CEXn XX01000A
Capture triggered by any transition on CEXn XX11000A
Software Timer XB00100A
High Speed Output XB00110A
Frequency Output XB00011A
8-Bit Pulse Width Modulator 0 B 0 0 C 0 1 A
16-Bit Pulse Width Modulator 1 B 0 0 C 0 1 A
Notes:
1. X = Don’t Care (no functional di fference for individual module if 1 or 0).
2. A = Enable interrupts for this module (PCA interrupt triggered on CCFn set to 1).
3. B = When set to 0, the di gital comparator is off. For high speed and frequency output modes, the asso ciated
pin will not toggle. In any of the PWM modes, this generates a 0% duty cycle (output = 0).
4. C = When set, a match event will cause the CCFn flag for the associated channel to be set.
C8051T600/1/2/3/4/5/6
164 Rev. 1.2
26.3.1. 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
transition 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 logic 1. 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
service routine, and must be cleared by software. If both CAPPn and CAPNn bits are set to logic 1, then
the state of the Port pin associated with CEXn can be read dire ctly to determine whether a rising-edge or
falling-edge caused the capture.
Figure 26.4. PCA Capture Mode Diagram
Note: The CEXn input signal must remain high or low for at least two system clock cycles to be recognized by the
hardware.
PCA0L
PCA0CPLn
PCA
Timebase
CEXn
CrossbarPort I/O
PCA0H
Capture
PCA0CPHn
0
1
0
1
(to CCFn)
PCA0CPMn
P
W
M
1
6
n
E
C
O
M
n
E
C
C
F
n
T
O
G
n
P
W
M
n
C
A
P
P
n
C
A
P
N
n
M
A
T
n
PCA0CN
C
FC
RC
C
F
0
C
C
F
2
C
C
F
1
PCA Interrupt
x 000xx
Rev. 1.2 165
C8051T600/1/2/3/4/5/6
26.3.2. Software Timer (Compare) Mode
In Software Timer mode, the PCA counter/timer value is compared to the module's 16-bit Capture/Com-
pare register (PCA0CPHn and PCA0CPLn). When a match occurs, t he Capture/Co mpare Flag (CCFn ) in
PCA0CN is set to logic 1. An interrupt request is generated if the CCFn interrupt for that module is
enabled. The CCFn bit is not automatica lly cleared by har dware wh en the CPU ve ctors to the interr upt ser-
vice routine, and must be cleared b y sof t ware. Settin g the ECOMn and MATn bits in the PCA0CPMn reg is-
ter enables Software Timer mode.
Important Note about Capture/Compare Registers: When writing a 16-bit value to the PCA0 Cap-
ture/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.
Figure 26.5. PCA Software Timer Mode Diagram
Match
16-bit Comparator
PCA0H
PCA0CPHn
Enable
PCA0L
PCA
Timebase
PCA0CPLn
00 00
0
1
x
ENB
ENB
0
1
Write to
PCA0CPLn
Write to
PCA0CPHn
Reset
PCA0CPMn
P
W
M
1
6
n
E
C
O
M
n
E
C
C
F
n
T
O
G
n
P
W
M
n
C
A
P
P
n
C
A
P
N
n
M
A
T
n
x
PCA0CN
C
FC
RC
C
F
0
C
C
F
2
C
C
F
1
PCA Interrupt
C8051T600/1/2/3/4/5/6
166 Rev. 1.2
26.3.3. 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 logic 1. An
interrupt request is generated if the CCFn interrupt for that module is enabled. The CCFn bit is not auto-
matically clear ed by hard ware wh en the C PU vectors to the inte rrupt serv ice rout ine, and m ust be cle ared
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 even t.
Important Note about Capture/Compare Registers: When writing a 16-bit value to the PCA0 Cap-
ture/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.
Figure 26.6. PCA High-Speed Output Mode Diagram
Match
16-bit Comparator
PCA0H
PCA0CPHn
Enable
PCA0L
PCA
Timebase
PCA0CPLn
0
1
00 0x
ENB
ENB
0
1
Write to
PCA0CPLn
Write to
PCA0CPHn
Reset
PCA0CPMn
P
W
M
1
6
n
E
C
O
M
n
E
C
C
F
n
T
O
G
n
P
W
M
n
C
A
P
P
n
C
A
P
N
n
M
A
T
n
x
CEXn Crossbar Port I/O
Toggle 0
1
TOGn
PCA0CN
C
FC
RC
C
F
0
C
C
F
2
C
C
F
1
PCA Interrupt
Rev. 1.2 167
C8051T600/1/2/3/4/5/6
26.3.4. 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
output is toggled. The frequency of the square wave is then defined by Equation 26.1.
Equation 26.1. Square Wave Frequency Output
Where FPCA is the frequency of the clock selected by the CPS2–0 bits in the PCA mode register,
PCA0MD. The lower byte of the capture/compare module is compared to the PCA counter low byte; on a
match, CEXn is toggled and the offset held in the high byte is added to the matche d value in PCA0CPLn.
Frequency Output Mode is enabled by setting the ECOMn, TOGn, and PWMn bits in the PCA0CPMn reg-
ister. Note that the MATn bit should normally be set to 0 in this mode. If the MATn bit is set to 1, the CC Fn
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.
Figure 26.7. PCA Frequency Output Mode
FCEXn FPCA
2PCA0CPHn×
-----------------------------------------
=
Note: A value of 0x00 in the PCA0CPHn register is equal to 256 for this equation.
8-bit
Comparator
PCA0L
Enable
PCA Timebase
match
PCA0CPHn8-bit AdderPCA0CPLn
Adder
Enable
CEXn Crossbar Port I/O
Toggle 0
1
TOGn
000 x
PCA0CPMn
P
W
M
1
6
n
E
C
O
M
n
E
C
C
F
n
T
O
G
n
P
W
M
n
C
A
P
P
n
C
A
P
N
n
M
A
T
n
x
ENB
ENB
0
1
Write to
PCA0CPLn
Write to
PCA0CPHn
Reset
C8051T600/1/2/3/4/5/6
168 Rev. 1.2
26.3.5. 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 th e CEXn pin will be set. When the count value in PCA0L overflows, the
CEXn output will be reset (see Figure 26.8). 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/Com-
pare high byte (PCA0CPHn) without software intervention. Setting the ECOMn and PWMn bits in the
PCA0CPMn register 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 (ris ing edge) occurs. The duty cycle for 8-
Bit PWM Mode is given in Equation 26.2.
Important Note about Capture/Compare Registers: When writing a 16-bit value to the PCA0 Cap-
ture/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.
Equation 26.2. 8-Bit PWM Duty Cycle
Using Equation 26.2, 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.
Figure 26.8. PCA 8-Bit PWM Mode Diagram
Duty Cycle 256 PCA0CPHn–()
256
---------------------------------------------------
=
8-bit
Comparator
PCA0L
PCA0CPLn
PCA0CPHn
CEXn Crossbar Port I/O
Enable
Overflow
PCA Timebase
00x0 x
Q
Q
SET
CLR
S
R
match
PCA0CPMn
P
W
M
1
6
n
E
C
O
M
n
E
C
C
F
n
T
O
G
n
P
W
M
n
C
A
P
P
n
C
A
P
N
n
M
A
T
n
0
ENB
ENB
0
1
Write to
PCA0CPLn
Write to
PCA0CPHn
Reset
COVF
Rev. 1.2 169
C8051T600/1/2/3/4/5/6
26.3.6. 16-Bit Pulse Width Modulator Mode
A PCA module may also be operated in 16-Bit PWM mode. 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 output on CEXn is asserted high; when the 16-bit counter overflows,
CEXn is asserted low. To output a varying duty cycle, new value writes should be sync hronized 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 varying 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 Equation 26.3.
Important Note about Capture/Compare Registers: When writing a 16-bit value to the PCA0 Cap-
ture/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.
Equation 26.3. 16-Bit PWM Duty Cycle
Using Equation 26.3, 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.
Figure 26.9. PCA 16-Bit PWM Mode
Duty Cycle 65536 PCA0CPn–()
65536
-----------------------------------------------------
=
PCA0CPLnPCA0CPHn
Enable
PCA Timebase
00x0 x
PCA0CPMn
P
W
M
1
6
n
E
C
O
M
n
E
C
C
F
n
T
O
G
n
P
W
M
n
C
A
P
P
n
C
A
P
N
n
M
A
T
n
1
16-bit Comparator CEXn Crossbar Port I/O
Overflow
Q
Q
SET
CLR
S
R
match
PCA0H PCA0L
ENB
ENB
0
1
Write to
PCA0CPLn
Write to
PCA0CPHn
Reset
C8051T600/1/2/3/4/5/6
170 Rev. 1.2
26.4. 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/disabl ed as ne ede d by so ftware.
With the WDTE bit set in the PCA0MD register, Module 2 operates as a Watchdog T imer (WDT). The Mod-
ule 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 option-
ally re-configured an d re-enabled if it is used in the system).
26.4.1. 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) ar e 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 Figure 26.10).
Figure 26.10. PCA Module 2 with Watchdog Timer Enabled
PCA0H
Enable
PCA0L Overflow
Reset
PCA0CPL2 8-bit Adder
PCA0CPH2
Adder
Enable
PCA0MD
C
I
D
L
W
D
T
E
E
C
F
C
P
S
1
C
P
S
0
W
D
L
C
K
C
P
S
2
Match
Write to
PCA0CPH2
8-bit
Comparator
Rev. 1.2 171
C8051T600/1/2/3/4/5/6
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, dependin g on the value of the PCA0L when the update is performed. The to tal of f-
set is then given (in PCA clocks) by Equation 26.4, where PCA0L is the value of the PCA0L register at the
time of the update.
Equation 26.4. 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.
26.4.2. Watchdog Timer Usage
To configure the WDT, perform the following tasks:
1. Disable the W DT by writing a 0 to the WDT E 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 se lect 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 WDLC K 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 Equation 26.4, this results in a WDT
timeout interval of 256 PCA clock cycles, or 3072 system clock cycles. Ta ble 26.3 lists some example tim-
eout intervals for typical system clocks.
Offset 256 PCA0CPL2×()256 PCA0L–()+=
C8051T600/1/2/3/4/5/6
172 Rev. 1.2
Table 26.3. 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
3,062,5002255 257
3,062,5002128 129.5
3,062,500232 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. 1.2 173
C8051T600/1/2/3/4/5/6
26.5. Register Descriptions for PCA0
Following are detailed descriptions of the special function registers related to the operation of the PCA.
SFR Address = 0xD8; Bit-Addressable
SFR Definition 26.1. PCA0CN: PCA Control
Bit76543210
Name CF CR CCF2 CCF1 CCF0
Type R/W R/W R R R R/W R/W R/W
Reset 00000000
Bit Name Function
7CF
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 th e PCA inte rrupt service r outin e. This b it is not au toma tically cleared
by hardware and must be cleared by software.
6CR
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 interrupt service rou-
tine. This bit is not autom atically cleared by hardware an d must be cleared by sof tware.
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 interrupt service rou-
tine. This bit is not autom atically cleared by hardware an d must be cleared by sof tware.
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 interrupt service rou-
tine. This bit is not autom atically cleared by hardware an d must be cleared by sof tware.
C8051T600/1/2/3/4/5/6
174 Rev. 1.2
SFR Address = 0xD9
SFR Definition 26.2. PCA0MD: PCA Mode
Bit76543210
Name CIDL WDTE WDLCK CPS[2:0] ECF
Type R/W R/W R/W R R/W R/W
Reset 01000000
Bit Name Function
7CIDL
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.
6WDTE
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 T imer E nable. When WDLCK is se t, the W atch dog
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)
11x: Reserved
0ECF
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 Wat c hdog Timer must first be di sabled.
Rev. 1.2 175
C8051T600/1/2/3/4/5/6
SFR Addresses: PCA0CPM0 = 0xDA, PCA0CPM1 = 0xDB, PCA0CPM2 = 0xDC
SFR Definition 26.3. PCA0CPMn: PCA Capture/Compare Mode
Bit76543210
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 00000000
Bit Name Function
7PWM16n
16-bit Pulse Width Modulation Enable.
This bit enables 16-bit mode when Pulse Width Modulation mode is enabled.
0: 8-bit PWM selected.
1: 16-bit PWM selected.
6ECOMn
Comparator Function Enable.
This bit enables the compar ator 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.
3MATn
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.
2TOGn
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 module oper-
ates in Frequency Output Mode.
1PWMn
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. The 8-bit PWM is used if
PWM16n is cleared; 16-bit mo de is used if PWM16n is set to logic 1. If the TOGn bit is
also set, the module operate s in Frequency Output Mode.
0ECCFn
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 T imer. To change the contents of the PCA0CPM2 register or the function of module 2, the
Watchdog Timer must be disabled.
C8051T600/1/2/3/4/5/6
176 Rev. 1.2
SFR Address = 0xF9
SFR Address = 0xFA
SFR Definition 26.4. PCA0L: PCA Counter/Timer Low Byte
Bit76543210
Name PCA0[7:0]
Type R/W R/W R/W R/W R/W R/W R/W R/W
Reset 00000000
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 26.5. PCA0H: PCA Counter/Timer High Byte
Bit76543210
Name PCA0[15:8]
Type R/W R/W R/W R/W R/W R/W R/W R/W
Reset 00000000
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 contents of PCA0L are read (see Section 26.1).
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. 1.2 177
C8051T600/1/2/3/4/5/6
SFR Addresses: PCA0CPL0 = 0xFB, PCA0CPL1 = 0xE9, PCA0CPL2 = 0xEB
SFR Addresses: PCA0CPH0 = 0xFC, PCA0CPH1 = 0xEA, PCA0CPH2 = 0xEC
SFR Definition 26.6. PCA0CPLn: PCA Capture Module Low Byte
Bit76543210
Name PCA0CPn[7:0]
Type R/W R/W R/W R/W R/W R/W R/W R/W
Reset 00000000
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.
Note: A write to this regi ster will clear the module’s ECOMn bi t to a 0.
SFR Definition 26.7. PCA0CPHn: PCA Capture Module High Byte
Bit76543210
Name PCA0CPn[15:8]
Type R/W R/W R/W R/W R/W R/W R/W R/W
Reset 00000000
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 capture module n.
Note: A write to this register will set the module’s ECOMn bit to a 1.
C8051T600/1/2/3/4/5/6
178 Rev. 1.2
27. C2 Interface
C8051T600/1/2/3/4/5/6 devices include an on-chip Silicon Labs 2-Wire (C2) debug interface to allow
EPROM programming and in-system debugging with the production part installed in the end application.
The C2 interface operates using only two pins: a bi-directional data signal (C2D), and a clock input
(C2CK). See the C2 Interface Specification for details on the C2 protocol.
27.1. C2 Interface Registers
The following describes the C2 registers necessary to perform EPROM programming functions through the
C2 interface. All C2 reg isters are accessed through the C2 interface as de scribed in the C2 Interfa ce Spec-
ification.
C2 Register Definition 27.1. C2ADD: C2 Address
Bit76543210
Name C2ADD[7:0]
Type R/W
Reset 00000000
Bit Name Function
7:0 C2ADD[7:0] Write: C2 Address.
Selects the target Data register for C2 Data Read and Data Write commands accord-
ing to the following list.
Address Name Description
0x00 DEVICEID Selects the Device ID Register (read only)
0x01 REVID Selects the Revision ID Register (read only)
0x02 DEVCTL Selects the C2 Device Control Register
0xDF EPCTL Selects the C2 EPROM Programming Control Register
0xBF EPDAT Selects the C2 EPROM Data Register
0xB7 EPSTAT Selects the C2 EPROM Status Register
0xAF EPADDRH Selects the C2 EPROM Address High Byte Register
0xAE EPADDRL Selects the C2 EPROM Address Low Byte Register
0xA9 CRC0 Selects the CRC0 Register
0xAA CRC1 Selects the CRC1 Register
0xAB CRC2 Selects the CRC2 Register
0xAC CRC3 Selects the CRC3 Register
Read: C2 Status
Returns status information on the current programming operation.
When the MS B (bit 7) is set to ‘1’, a read or writ e op er at ion is in progr es s . Al l ot he r
bits can be ignored by the programming tools.
Rev. 1.2 179
C8051T600/1/2/3/4/5/6
C2 Address: 0x00
C2 Address: 0x01
C2 Register Definition 27.2. DEVICEID: C2 Device ID
Bit76543210
Name DEVICEID[7:0]
Type R/W
Reset 00010111
Bit Name Function
7:0 DEVICEID[7:0] Device ID.
This read-only register returns the 8-bit device ID:
0x10 = C8051T600/1/2/3/4/5
0x1B = C8051T606
C2 Register Definition 27.3. REVID: C2 Revision ID
Bit76543210
Name REVID[7:0]
Type R/W
Reset Varies Varies Varies Varies Varies Varies Varies Varies
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.
C8051T600/1/2/3/4/5/6
180 Rev. 1.2
C2 Address: 0x02
C2 Address: 0xDF
C2 Register Definition 27.4. DEVCTL: C2 Device Control
Bit76543210
Name DEVCTL[7:0]
Type R/W
Reset 00000000
Bit Name Function
7:0 DEVCTL[7:0] Device Control Register.
This register is used to halt the device for EPROM operations via the C2 interface.
Refer to the EPROM chapter for more information.
C2 Register Definition 27.5. EPCTL: EPROM Programming Control Register
Bit76543210
Name EPCTL[7:0]
Type R/W
Reset 00000000
Bit Name Function
7:0 EPCTL[7:0] EPROM Programming Control Register.
This register is used to enable EPROM programming via the C2 interface. Refer to
the EPROM chapter for more information.
Rev. 1.2 181
C8051T600/1/2/3/4/5/6
C2 Address: 0xBF
C2 Address: 0xB7
C2 Register Definition 27.6. EPDAT: C2 EPROM Data
Bit76543210
Name EPDAT[7:0]
Type R/W
Reset 00000000
Bit Name Function
7:0 EPDAT[7:0] C2 EPROM Data Register.
This register is used to pass EPROM data during C2 EPROM operations.
C2 Register Definition 27.7. EPSTAT: C2 EPROM Status
Bit76543210
Name WRLOCK RDLOCK ERROR
Type RRRRRRRR
Reset 00000000
Bit Name Function
7WRLOCK
Write Lock Indicator.
Set to 1 if EPADDR currently points to a write-locked address.
6 RDLOCK Read Lock Indicator.
Set to 1 if EPADDR currently points to a read-locked address.
5:1 Unused Unused. Read = Varies; Write = Don’t Care.
0ERROR
Error Indicator.
Set to 1 if last EPROM read or write operation failed due to a security restriction.
C8051T600/1/2/3/4/5/6
182 Rev. 1.2
C2 Address: 0xAF
C2 Address: 0xAE
C2 Register Definition 27.8. EPADDRH: C2 EPROM Address High Byte
Bit76543210
Name EPADDR[15:8]
Type R/W
Reset 00000000
Bit Name Function
7:0 EPADDR[15:8] C2 EPROM Address High Byte.
This register is used to set the EPROM address location duri ng C2 EPROM oper-
ations.
C2 Register Definition 27.9. EPADDRL: C2 EPROM Address Low Byte
Bit76543210
Name EPADDR[7:0]
Type R/W
Reset 00000000
Bit Name Function
7:0 EPADDR[15:8] C2 EPROM Address Low Byte.
This register is used to set the EPROM address location duri ng C2 EPROM oper-
ations.
Rev. 1.2 183
C8051T600/1/2/3/4/5/6
C2 Address: 0xA9
C2 Address: 0xAA
C2 Register Definition 27.10. CRC0: CRC Byte 0
Bit76543210
Name CRC[7:0]
Type R/W
Reset 00000000
Bit Name Function
7:0 CRC[7:0] CRC Byte 0.
A write to this register initiates a 16-bit CRC of one 256-byte block of EPROM mem-
ory. The byte written to CRC0 is the upper byte of the 16-bit address where the CRC
will begin. The lower byte of the beginning address is always 0x00. When complete,
the 16-bit result will be available in CRC1 (MSB) and CRC0 (LSB). See Section
“20.3. Program Memory CRC” on page 99.
C2 Register Definition 27.11. CRC1: CRC Byte 1
Bit76543210
Name CRC[15:8]
Type R/W
Reset 00000000
Bit Name Function
7:0 CRC[15:8] CRC Byte 1.
A write to this register initiates a 32-bit CRC on the entir e pr og ra m mem o ry space.
The CRC begins at address 0x0000. When complete, the 32-bit result is stored in
CRC3 (MSB), CRC2, CRC1, and CRC0 (LSB). See Section “20.3. Program Memory
CRC” on page 99.
C8051T600/1/2/3/4/5/6
184 Rev. 1.2
C2 Address: 0xAB
C2 Address: 0xAC
C2 Register Definition 27.12. CRC2: CRC Byte 2
Bit76543210
Name CRC[23:16]
Type R/W
Reset 00000000
Bit Name Function
7:0 CRC[23:16] CRC Byte 2.
See Section “20.3. Program Memory CRC” on page 99.
C2 Register Definition 27.13. CRC3: CRC Byte 3
Bit76543210
Name CRC[31:24]
Type R/W
Reset 00000000
Bit Name Function
7:0 CRC[31:24] CRC Byte 3.
See Section “20.3. Program Memory CRC” on page 99.
Rev. 1.2 185
C8051T600/1/2/3/4/5/6
27.2. C2 Pin Sharing
The C2 protocol allows the C2 pins to be shared with user functions so that in-system debugging and
EPROM programming functions may be performed. This is possible because C2 communication is typi-
cally performed when the device is in the halt state, where all on-chip peripherals and user software are
stalled. In this halte d st ate, the C2 interface can safely ‘borrow’ the C2CK (normally RST) and C2D pins. In
most applications, external resistors are required to isolate C2 interface traffic from the user application
when performing debug functions. Th ese extern al resistors are no t necessa ry for production boards. A typ-
ical isolation configuration is shown in Figure 27.1.
Figure 27.1. Typical C2 Pin Sharing
The configuration in Figure 27.1 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.
C2D
C2CK
Reset (a)
Input (b)
Output (c)
C2 Interface Master
C8051T600/1/2/3/4/5/6
186 Rev. 1.2
DOCUMENT CHANGE LIST
Revision 0.5 to Revision 1.0
Updated electrical specification tables based on test, characterization, and qualification data.
Updated with new formatting standards.
Corrected minor typographical errors throughout document.
Updated wording from “OTP EPROM” to “EPROM” throughout document.
Added information on C2 EPSTAT Register.
Updated EPROM programming sequence.
Added Note about 100% Tin (Sn) lead finish to ordering information table.
Updated packaging information to include JEDEC-standard drawings for package and land diagram.
Revision 1.0 to Revision 1.1
Added C8051T606 device information.
Revision 1.1 to Revision 1.2
Updated Table 8.4 on page 34.
Rev. 1.2 187
C8051T600/1/2/3/4/5/6
NOTES:
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