SILABS C8051F855-B-GU Low-cost 8-bit mcu family with up to 8 kb of flash Datasheet

C8051F85x/86x
Low-Cost 8-bit MCU Family with up to 8 kB of Flash
Memory
- Up to 8 kB flash
- Flash is in-system programmable in 512-Byte sectors
- Up to 512 Bytes RAM (256 + 256)
On-Chip Debug
- On-chip debug circuitry facilitates full speed, non-intrusive in-
12-Bit Analog-to-Digital Converter
- Up to 16 input channels
- Up to 200 ksps 12-bit mode or 800 ksps 10-bit mode
- Internal VREF or external VREF supported
Communication Peripherals
- UART
- I2C / SMBus™
- SPI™
Internal Low-Power Oscillator
- Calibrated to 24.5 MHz
- Low supply current
- ±2% accuracy over supply and temperature
Timer/Counters and PWM
- 4 General-Purpose 16-bit Timer/Counters
- 16-bit Programmable Counter Array (PCA) with three channels
of PWM, capture/compare, or frequency output capability, and
hardware kill/safe state capability
Internal Low-Frequency Oscillator
- 80 kHz nominal operation
- Low supply current
- Independent clock source for watchdog timer
Supply Voltage
- 2.2 to 3.6 V
Package Options
- 16-pin SOIC
- 20-pin QFN, 3 x 3 mm
- 24-pin QSOP
- Available in die form
- Qualified to AEC-Q100 Standards
2 Analog Comparators
- Programmable hysteresis and response time
- Configurable as interrupt or reset source
- Low current
Additional Support Peripherals
- Independent watchdog timer clocked from LFO
- 16-bit CRC engine
Temperature Ranges:
- –40 to +125 °C (-Ix) and –40 to +85 °C (-Gx)
Core LDO
CIP-51
(25 MHz)
Watchdog
I2C / SMBus
Supply Monitor
16-bit CRC
Clocking / Oscillators
24.5 MHz Low Power Oscillator
80 kHz Low Frequency Oscillator
External Clock (CMOS Input)
SPI
4 x 16-bit Timers
3-Channel PCA
Clock Selection
C2 Serial Debug / Programming
Preliminary Rev 0.6 7/13
UART
Analog Peripherals
SAR ADC
(12-bit 200 ksps,10-bit 800 ksps)
Voltage Reference
2 x Low Current Comparators
Copyright © 2013 by Silicon Laboratories
18 Multi-Function 5V-Tolerant I/O Pins
256-512 B RAM
Digital Peripherals
Priority Crossbar
Encoder
Core / Memory / Support
2-8 kB Flash
General-Purpose I/O
- Up to 18 pins
- 5 V-Tolerant
- Crossbar-enabled
Flexible Pin Muxing
-
system debug (no emulator required)
Provides breakpoints, single stepping, inspect/modify memory
and registers
High-Speed CIP-51 µC Core
- Efficient, pipelined instruction architecture
- Up to 25 MIPS throughput with 25 MHz clock
- Uses standard 8051 instruction set
- Expanded interrupt handler
C8051F85x/86x
This information applies to a product under development. Its characteristics and specifications are subject to change without notice.
C8051F85x/86x
Ta ble of Contents
1. Electrical Specifications......................................................................................................7
1.1. Electrical Characteristics ................................................................................................7
1.2. Typical Power Curves .................................................................................................. 17
1.2.1. Operating Supply Current .................................................................................... 17
1.2.2. ADC Supply Current ............................................................................................ 18
1.3. Thermal Conditions ...................................................................................................... 19
1.4. Absolute Maximum Ratings..........................................................................................19
2. System Overview ...............................................................................................................20
2.1. Power ........................................................................................................................... 22
2.1.1. LDO .................................................................................................................. 22
2.1.2. Voltage Supply Monitor (VMON0) ....................................................................... 22
2.1.3. Device Power Modes........................................................................................... 22
2.2. I/O................................................................................................................................. 23
2.2.1. General Features.................................................................................................23
2.2.2. Crossbar .............................................................................................................. 23
2.3. Clocking........................................................................................................................ 24
2.4. Counters/Timers and PWM ..........................................................................................24
2.4.1. Programmable Counter Array (PCA0) ................................................................. 24
2.4.2. Timers (Timer 0, Timer 1, Timer 2 and Timer 3).................................................. 24
2.4.3. Watchdog Timer (WDT0)..................................................................................... 24
2.5. Communications and other Digital Peripherals ............................................................ 25
2.5.1. Universal Asynchronous Receiver/Transmitter (UART0) .................................... 25
2.5.2. Serial Peripheral Interface (SPI0) ........................................................................ 25
2.5.3. System Management Bus / I2C (SMBus0) .......................................................... 25
2.5.4. 16/32-bit CRC (CRC0)......................................................................................... 25
2.6. Analog Peripherals ....................................................................................................... 26
2.6.1. 12-Bit Analog-to-Digital Converter (ADC0) .......................................................... 26
2.6.2. Low Current Comparators (CMP0, CMP1) .......................................................... 26
2.7. Reset Sources..............................................................................................................27
2.8. On-Chip Debugging...................................................................................................... 27
3. Pin Definitions.................................................................................................................... 28
3.1. C8051F850/1/2/3/4/5 QSOP24 Pin Definitions ............................................................ 28
3.2. C8051F850/1/2/3/4/5 QFN20 Pin Definitions ............................................................... 31
3.3. C8051F860/1/2/3/4/5 SOIC16 Pin Definitions..............................................................34
4. Ordering Information .........................................................................................................37
5. QSOP-24 Package Specifications .................................................................................... 39
6. QFN-20 Package Specifications ....................................................................................... 41
7. SOIC-16 Package Specifications ...................................................................................... 44
8. Memory Organization ........................................................................................................46
8.1. Program Memory.......................................................................................................... 47
8.1.1. MOVX Instruction and Program Memory............................................................. 47
8.2. Data Memory................................................................................................................ 47
8.2.1. Internal RAM........................................................................................................47
8.2.2. External RAM....................................................................................................... 48
2
Preliminary Rev 0.6
C8051F85x/86x
8.2.3. Special Function Registers .................................................................................. 48
9. Special Function Register Memory Map.......................................................................... 49
10. Flash Memory..................................................................................................................... 54
10.1.Security Options........................................................................................................... 54
10.2.Programming The Flash Memory ................................................................................ 56
10.2.1.Flash Lock and Key Functions ............................................................................56
10.2.2.Flash Erase Procedure........................................................................................ 56
10.2.3.Flash Write Procedure......................................................................................... 56
10.3.Non-volatile Data Storage............................................................................................ 57
10.4.Flash Write and Erase Guidelines ............................................................................... 57
10.4.1.Voltage Supply Maintenance and the Supply Monitor.........................................57
10.4.2.PSWE Maintenance ............................................................................................ 57
10.4.3.System Clock....................................................................................................... 58
10.5.Flash Control Registers ............................................................................................... 59
11. Device Identification .......................................................................................................... 62
11.1.Device Identification Registers..................................................................................... 62
12. Interrupts ............................................................................................................................ 65
12.1.MCU Interrupt Sources and Vectors ............................................................................65
12.1.1.Interrupt Priorities ................................................................................................ 65
12.1.2.Interrupt Latency.................................................................................................. 65
12.2.Interrupt Control Registers........................................................................................... 67
13. Power Management and Internal Regulator .................................................................... 74
13.1.Power Modes ...............................................................................................................74
13.1.1.Idle Mode............................................................................................................. 74
13.1.2.Stop Mode ........................................................................................................... 75
13.2.LDO Regulator .............................................................................................................75
13.3.Power Control Registers .............................................................................................. 75
13.4.LDO Control Registers.................................................................................................76
14. Analog-to-Digital Converter (ADC0)................................................................................. 78
14.1.ADC0 Analog Multiplexer............................................................................................. 79
14.2.ADC Operation.............................................................................................................80
14.2.1.Starting a Conversion ..........................................................................................80
14.2.2.Tracking Modes ................................................................................................... 80
14.2.3.Burst Mode .......................................................................................................... 81
14.2.4.Settling Time Requirements ................................................................................ 82
14.2.5.Gain Setting......................................................................................................... 83
14.3.8-Bit Mode.................................................................................................................... 83
14.4.12-Bit Mode.................................................................................................................. 83
14.5.Power Considerations.................................................................................................. 84
14.6.Output Code Formatting .............................................................................................. 86
14.7.Programmable Window Detector ................................................................................. 87
14.7.1.Window Detector In Single-Ended Mode............................................................. 87
14.8.Voltage and Ground Reference Options...................................................................... 89
14.8.1.External Voltage Reference................................................................................. 89
14.8.2.Internal Voltage Reference.................................................................................. 89
14.8.3.Analog Ground Reference...................................................................................89
Preliminary Rev 0.6
3
C8051F85x/86x
14.9.Temperature Sensor .................................................................................................... 90
14.9.1.Calibration ........................................................................................................... 90
14.10.ADC Control Registers............................................................................................... 91
15. CIP-51 Microcontroller Core ........................................................................................... 106
15.1.Performance .............................................................................................................. 106
15.2.Programming and Debugging Support ...................................................................... 107
15.3.Instruction Set ............................................................................................................ 107
15.3.1.Instruction and CPU Timing............................................................................... 107
15.4.CPU Core Registers .................................................................................................. 112
16. Clock Sources and Selection (HFOSC0, LFOSC0, and EXTCLK)................................ 118
16.1.Programmable High-Frequency Oscillator................................................................. 118
16.2.Programmable Low-Frequency Oscillator.................................................................. 118
16.2.1.Calibrating the Internal L-F Oscillator ................................................................ 118
16.3.External Clock............................................................................................................118
16.4.Clock Selection .......................................................................................................... 119
16.5.High Frequency Oscillator Control Registers............................................................. 120
16.6.Low Frequency Oscillator Control Registers.............................................................. 121
16.7.Clock Selection Control Registers ............................................................................. 122
17. Comparators (CMP0 and CMP1)..................................................................................... 123
17.1.System Connectivity .................................................................................................. 123
17.2.Functional Description ...............................................................................................126
17.3.Comparator Control Registers ................................................................................... 127
18. Cyclic Redundancy Check Unit (CRC0)......................................................................... 133
18.1.CRC Algorithm ........................................................................................................... 133
18.2.Preparing for a CRC Calculation................................................................................ 135
18.3.Performing a CRC Calculation................................................................................... 135
18.4.Accessing the CRC0 Result....................................................................................... 135
18.5.CRC0 Bit Reverse Feature ........................................................................................135
18.6.CRC Control Registers .............................................................................................. 136
19. External Interrupts (INT0 and INT1)................................................................................ 142
19.1.External Interrupt Control Registers........................................................................... 143
20. Programmable Counter Array (PCA0)............................................................................ 146
20.1.PCA Counter/Timer.................................................................................................... 147
20.2.PCA0 Interrupt Sources ............................................................................................. 147
20.3.Capture/Compare Modules........................................................................................148
20.3.1.Output Polarity................................................................................................... 148
20.3.2.Edge-triggered Capture Mode ........................................................................... 149
20.3.3.Software Timer (Compare) Mode ...................................................................... 150
20.3.4.High-Speed Output Mode.................................................................................. 151
20.3.5.Frequency Output Mode.................................................................................... 152
20.4.PWM Waveform Generation ...................................................................................... 153
20.4.1.Edge Aligned PWM ........................................................................................... 153
20.4.2.Center Aligned PWM ......................................................................................... 155
20.4.3. 8 to11-bit Pulse Width Modulator Modes.......................................................... 157
20.4.4. 16-Bit Pulse Width Modulator Mode ................................................................. 158
20.5.Comparator Clear Function........................................................................................159
4
Preliminary Rev 0.6
C8051F85x/86x
20.6.PCA Control Registers...............................................................................................160
21. Port I/O (Port 0, Port 1, Port 2, Crossbar, and Port Match) .......................................... 178
21.1.General Port I/O Initialization ..................................................................................... 179
21.2.Assigning Port I/O Pins to Analog and Digital Functions ........................................... 180
21.2.1.Assigning Port I/O Pins to Analog Functions.....................................................180
21.2.2.Assigning Port I/O Pins to Digital Functions ...................................................... 180
21.2.3.Assigning Port I/O Pins to Fixed Digital Functions ............................................ 181
21.3.Priority Crossbar Decoder.......................................................................................... 182
21.4.Port I/O Modes of Operation ...................................................................................... 184
21.4.1.Configuring Port Pins For Analog Modes .......................................................... 184
21.4.2.Configuring Port Pins For Digital Modes ........................................................... 184
21.4.3.Port Drive Strength ............................................................................................ 184
21.5.Port Match.................................................................................................................. 185
21.6.Direct Read/Write Access to Port I/O Pins................................................................. 185
21.7.Port I/O and Pin Configuration Control Registers ...................................................... 186
22. Reset Sources and Supply Monitor ............................................................................... 204
22.1.Power-On Reset ........................................................................................................ 205
22.2.Power-Fail Reset / Supply Monitor ............................................................................ 206
22.3.Enabling the VDD Monitor ......................................................................................... 206
22.4.External Reset ........................................................................................................... 207
22.5.Missing Clock Detector Reset.................................................................................... 207
22.6.Comparator0 Reset.................................................................................................... 207
22.7.Watchdog Timer Reset .............................................................................................. 207
22.8.Flash Error Reset....................................................................................................... 207
22.9.Software Reset .......................................................................................................... 207
22.10.Reset Sources Control Registers............................................................................. 208
23. Serial Peripheral Interface (SPI0) ................................................................................... 214
23.1.Signal Descriptions .................................................................................................... 215
23.1.1.Master Out, Slave In (MOSI) ............................................................................. 215
23.1.2.Master In, Slave Out (MISO) ............................................................................. 215
23.1.3.Serial Clock (SCK)............................................................................................. 215
23.1.4.Slave Select (NSS)............................................................................................ 215
23.2.SPI0 Master Mode Operation .................................................................................... 216
23.3.SPI0 Slave Mode Operation ...................................................................................... 218
23.4.SPI0 Interrupt Sources...............................................................................................218
23.5.Serial Clock Phase and Polarity.................................................................................218
23.6.SPI Special Function Registers .................................................................................220
23.7.SPI Control Registers ................................................................................................ 224
24. System Management Bus / I2C (SMBus0) ..................................................................... 229
24.1.Supporting Documents .............................................................................................. 230
24.2.SMBus Configuration ................................................................................................. 230
24.3.SMBus Operation....................................................................................................... 230
24.3.1.Transmitter vs. Receiver.................................................................................... 231
24.3.2.Arbitration .......................................................................................................... 231
24.3.3.Clock Low Extension ......................................................................................... 231
24.3.4.SCL Low Timeout .............................................................................................. 231
Preliminary Rev 0.6
5
C8051F85x/86x
24.3.5.SCL High (SMBus Free) Timeout...................................................................... 232
24.4.Using the SMBus ....................................................................................................... 232
24.4.1.SMBus Configuration Register ..........................................................................232
24.4.2.SMBus Pin Swap...............................................................................................234
24.4.3.SMBus Timing Control....................................................................................... 234
24.4.4.SMB0CN Control Register.................................................................................234
24.4.5.Hardware Slave Address Recognition............................................................... 236
24.4.6.Data Register..................................................................................................... 236
24.5.SMBus Transfer Modes ............................................................................................. 237
24.5.1.Write Sequence (Master)................................................................................... 237
24.5.2.Read Sequence (Master) .................................................................................. 238
24.5.3.Write Sequence (Slave)..................................................................................... 239
24.5.4.Read Sequence (Slave) .................................................................................... 240
24.6.SMBus Status Decoding ............................................................................................ 240
24.7.I2C / SMBus Control Registers .................................................................................. 245
25. Timers (Timer0, Timer1, Timer2 and Timer3) ................................................................ 252
25.1.Timer 0 and Timer 1................................................................................................... 253
25.1.1.Mode 0: 13-bit Counter/Timer............................................................................ 254
25.1.2.Mode 1: 16-bit Counter/Timer............................................................................ 254
25.1.3.Mode 2: 8-bit Counter/Timer with Auto-Reload ................................................. 255
25.1.4.Mode 3: Two 8-bit Counter/Timers (Timer 0 Only) ............................................ 256
25.2.Timer 2 and Timer 3................................................................................................... 257
25.2.1.16-bit Timer with Auto-Reload ........................................................................... 257
25.2.2.8-bit Timers with Auto-Reload ........................................................................... 258
25.2.3.Capture Mode.................................................................................................... 259
25.3.Timer Control Registers ............................................................................................. 260
26. Universal Asynchronous Receiver/Transmitter (UART0) ............................................ 278
26.1.Enhanced Baud Rate Generation .............................................................................. 278
26.2.Operational Modes..................................................................................................... 280
26.2.1.8-Bit UART ........................................................................................................ 280
26.2.2.9-Bit UART ........................................................................................................ 281
26.3.Multiprocessor Communications................................................................................ 282
26.4.UART Control Registers ............................................................................................ 284
27. Watchdog Timer (WDT0) ................................................................................................. 288
27.1.Enabling / Resetting the WDT.................................................................................... 289
27.2.Disabling the WDT ..................................................................................................... 289
27.3.Disabling the WDT Lockout ....................................................................................... 289
27.4.Setting the WDT Interval............................................................................................ 289
27.5.Watchdog Timer Control Registers............................................................................ 290
28. C2 Interface ...................................................................................................................... 292
28.1.C2 Pin Sharing........................................................................................................... 292
28.2.C2 Interface Registers ...............................................................................................293
Document Change List ......................................................................................................... 298
Contact Information .............................................................................................................. 299
6
Preliminary Rev 0.6
1. Electrical Specifications
1.1. Electrical Characteristics
All electrical parameters in all tables are specified under the conditions listed in Table 1.1, unless stated otherwise.
Table 1.1. Recommended Operating Conditions
Parameter
Operating Supply Voltage on VDD
System Clock Frequency
Operating Ambient Temperature
Operating Junction Temperature
Symbol
Min
Typ
Max
Unit
VDD
2.2
—
3.6
V
fSYSCLK
0
—
25
MHz
Commercial Grade Devices
(-GM, -GS, -GU)
–40
—
85
°C
Industrial Grade Devices
(-IM, -IS, -IU)
–40
—
125
°C
Commercial Grade Devices
(-GM, -GS, -GU)
–40
—
TBD
°C
Industrial Grade Devices
(-IM, -IS, -IU)
–40
—
TBD
°C
TA
TJ
Test Condition
Note: All voltages with respect to GND
Table 1.2. Power Consumption
Parameter
Symbol
Test Condition
Min
Typ
Max
Unit
IDD
FSYSCLK = 24.5 MHz2
—
4.45
TBD
mA
FSYSCLK = 1.53 MHz2
—
915
TBD
A
FSYSCLK = 80 kHz3
Digital Core Supply Current
Normal Mode—Full speed with
code executing from flash
Idle Mode—Core halted with
peripherals running
Stop Mode—Core halted and all
clocks stopped, Supply monitor off.
IDD
IDD
—
250
TBD
A
2
—
2.05
TBD
mA
FSYSCLK = 1.53 MHz2
—
550
TBD
A
FSYSCLK = 80 kHz3
—
125
TBD
A
Internal LDO ON
—
105
—
A
Internal LDO OFF
—
0.2
—
A
FSYSCLK = 24.5 MHz
Notes:
1. Currents are additive. For example, where IDD is specified and the mode is not mutually exclusive, enabling the
functions increases supply current by the specified amount.
2. Includes supply current from internal regulator, supply monitor, and High Frequency Oscillator
3. Includes supply current from internal regulator, supply monitor, and Low Frequency Oscillator
4. ADC0 always-on power excludes internal reference supply current
5. The internal reference is enabled as-needed when operating the ADC in burst mode to save power.
Preliminary Rev 0.6
7
Electrical Specifications
C8051F85x/86x
Electrical Specifications
C8051F85x/86x
Table 1.2. Power Consumption (Continued)
Parameter
Symbol
Test Condition
Min
Typ
Max
Unit
High-Frequency Oscillator
IHFOSC
Operating at 24.5 MHz,
TA = 25 °C
—
155
—
µA
Low-Frequency Oscillator
ILFOSC
Operating at 80 kHz,
TA = 25 °C
—
3.5
—
µA
IADC
800 ksps, 10-bit conversions or
200 ksps, 12-bit conversions
Normal bias settings
VDD = 3.0 V
—
845
TBD
µA
250 ksps, 10-bit conversions or
62.5 ksps 12-bit conversions
Low power bias settings
VDD = 3.0 V
—
425
TBD
µA
200 ksps, VDD = 3.0 V
—
370
—
µA
100 ksps, VDD = 3.0 V
—
185
—
µA
10 ksps, VDD = 3.0 V
—
19
—
µA
200 ksps, VDD = 3.0 V
—
490
—
µA
100 ksps, VDD = 3.0 V
—
245
—
µA
10 ksps, VDD = 3.0 V
—
23
—
µA
100 ksps, VDD = 3.0 V
—
530
—
µA
50 ksps, VDD = 3.0 V
—
265
—
µA
10 ksps, VDD = 3.0 V
—
53
—
µA
100 ksps, VDD = 3.0 V,
Normal bias
—
950
—
µA
50 ksps, VDD = 3.0 V,
Low power bias
—
420
—
µA
10 ksps, VDD = 3.0 V,
Low power bias
—
85
—
µA
Normal Power Mode
—
680
TBD
µA
Low Power Mode
—
160
TBD
µA
—
75
TBD
µA
Analog Peripheral Supply Currents
ADC0 Always-on4
ADC0 Burst Mode, 10-bit single
conversions, external reference
ADC0 Burst Mode, 10-bit single
conversions, internal reference,
Low power bias settings
ADC0 Burst Mode, 12-bit single
conversions, external reference
ADC0 Burst Mode, 12-bit single
conversions, internal reference
Internal ADC0 Reference, Alwayson5
Temperature Sensor
IADC
IADC
IADC
IADC
IIREF
ITSENSE
Notes:
1. Currents are additive. For example, where IDD is specified and the mode is not mutually exclusive, enabling the
functions increases supply current by the specified amount.
2. Includes supply current from internal regulator, supply monitor, and High Frequency Oscillator
3. Includes supply current from internal regulator, supply monitor, and Low Frequency Oscillator
4. ADC0 always-on power excludes internal reference supply current
5. The internal reference is enabled as-needed when operating the ADC in burst mode to save power.
8
Preliminary Rev 0.6
Table 1.2. Power Consumption (Continued)
Parameter
Symbol
Test Condition
Min
Typ
Max
Unit
ICMP
CPnMD = 11
—
0.5
—
µA
CPnMD = 10
—
3
—
µA
CPnMD = 01
—
10
—
µA
CPnMD = 00
—
25
—
µA
IVMON
—
15
TBD
µA
Write Operation
IFLASH-W
—
—
TBD
mA
Erase Operation
IFLASH-E
—
—
TBD
mA
Comparator 0 (CMP0),
Comparator 1 (CMP1)
Voltage Supply Monitor (VMON0)
Flash Current on VDD
Notes:
1. Currents are additive. For example, where IDD is specified and the mode is not mutually exclusive, enabling the
functions increases supply current by the specified amount.
2. Includes supply current from internal regulator, supply monitor, and High Frequency Oscillator
3. Includes supply current from internal regulator, supply monitor, and Low Frequency Oscillator
4. ADC0 always-on power excludes internal reference supply current
5. The internal reference is enabled as-needed when operating the ADC in burst mode to save power.
Preliminary Rev 0.6
9
Electrical Specifications
C8051F85x/86x
Electrical Specifications
C8051F85x/86x
Table 1.3. Reset and Supply Monitor
Parameter
VDD Supply Monitor Threshold
Power-On Reset (POR) Threshold
Symbol
Test Condition
Min
Typ
Max
Unit
1.85
1.95
2.1
V
Rising Voltage on VDD
—
1.4
—
V
Falling Voltage on VDD
0.8
—
1.3
V
VVDDM
VPOR
VDD Ramp Time
tRMP
Time to VDD > 2.2 V
10
—
3000
µs
Reset Delay from POR
tPOR
Relative to VDD >
VPOR
3
—
TBD
ms
Reset Delay from non-POR source
tRST
Time between release
of reset source and
code execution
—
30
—
µs
RST Low Time to Generate Reset
tRSTL
15
—
—
µs
Missing Clock Detector Response
Time (final rising edge to reset)
tMCD
—
0.625
1.2
ms
Missing Clock Detector Trigger 
Frequency
FMCD
—
7.5
13
kHz
VDD Supply Monitor Turn-On Time
tMON
—
2
—
µs
FSYSCLK > 1 MHz
Table 1.4. Flash Memory
Parameter
Write Time1
Erase Time1
VDD Voltage During
Programming2
Endurance (Write/Erase Cycles)
Symbol
Test Condition
Min
Typ
Max
Units
tWRITE
One Byte
TBD
20
TBD
µs
tERASE
One Page
TBD
5
TBD
ms
VPROG
2.2
—
3.6
V
NWE
20k
100k
—
Cycles
Notes:
1. Does not include sequencing time before and after the write/erase operation, which may be multiple SYSCLK cycles.
2. Flash can be safely programmed at any voltage above the supply monitor threshold (VVDDM).
3. Data Retention Information is published in the Quarterly Quality and Reliability Report.
10
Preliminary Rev 0.6
Table 1.5. Internal Oscillators
Parameter
Symbol
Test Condition
Min
Typ
Max
Unit
fHFOSC
Full Temperature and
Supply Range
24
24.5
25
MHz
Power Supply Sensitivity
PSSHFOSC
TA = 25 °C
—
0.5
—
%/V
Temperature Sensitivity
TSHFOSC
VDD = 3.0 V
—
40
—
ppm/°C
fLFOSC
Full Temperature and
Supply Range
75
80
85
kHz
Power Supply Sensitivity
PSSLFOSC
TA = 25 °C
—
0.05
—
%/V
Temperature Sensitivity
TSLFOSC
VDD = 3.0 V
—
65
—
ppm/°C
Test Condition
Min
Typ
Max
Unit
High Frequency Oscillator (24.5 MHz)
Oscillator Frequency
Low Frequency Oscillator (80 kHz)
Oscillator Frequency
Table 1.6. External Clock Input
Parameter
Symbol
External Input CMOS Clock
Frequency (at EXTCLK pin)
fCMOS
0
—
25
MHz
External Input CMOS Clock High Time
tCMOSH
18
—
—
ns
External Input CMOS Clock Low Time
tCMOSL
18
—
—
ns
Preliminary Rev 0.6
11
Electrical Specifications
C8051F85x/86x
Electrical Specifications
C8051F85x/86x
Table 1.7. ADC
Parameter
Resolution
Symbol
Test Condition
Nbits
12 Bit Mode
12
Bits
10 Bit Mode
10
Bits
Throughput Rate
(High Speed Mode)
fS
Throughput Rate
(Low Power Mode)
fS
Tracking Time
tTRK
Power-On Time
tPWR
SAR Clock Frequency
fSAR
Min
Typ
Max
Unit
12 Bit Mode
—
—
200
ksps
10 Bit Mode
—
—
800
ksps
12 Bit Mode
—
—
62.5
ksps
10 Bit Mode
—
—
250
ksps
High Speed Mode
230
—
—
ns
Low Power Mode
450
—
—
ns
1.2
—
—
µs
High Speed Mode,
Reference is 2.4 V internal
—
—
6.25
MHz
High Speed Mode,
Reference is not 2.4 V internal
—
—
12.5
MHz
Low Power Mode
—
—
4
MHz
Conversion Time
tCNV
10-Bit Conversion,
SAR Clock = 12.25 MHz,
System Clock = 24.5 MHz.
1.1
µs
Sample/Hold Capacitor
CSAR
Gain = 1
—
5
—
pF
Gain = 0.5
—
2.5
—
pF
Input Pin Capacitance
CIN
—
20
—
pF
Input Mux Impedance
RMUX
—
550
—

Voltage Reference Range
VREF
1
—
VDD
V
Gain = 1
0
—
VREF
V
Gain = 0.5
0
—
2xVREF
V
—
70
—
dB
12 Bit Mode
—
±1
±1.9
LSB
10 Bit Mode
—
±0.2
±0.5
LSB
12 Bit Mode
–1
±0.7
1.8
LSB
10 Bit Mode
—
±0.2
±0.5
LSB
Input Voltage Range*
Power Supply Rejection
Ratio
VIN
PSRRADC
DC Performance
Integral Nonlinearity
Differential Nonlinearity 
(Guaranteed Monotonic)
INL
DNL
*Note: Absolute input pin voltage is limited by the VDD supply.
12
Preliminary Rev 0.6
Table 1.7. ADC (Continued)
Parameter
Offset Error
Offset Temperature Coefficient
Slope Error
Symbol
Test Condition
Min
Typ
Max
Unit
EOFF
12 Bit Mode, VREF = 1.65 V
–2
0
2
LSB
10 Bit Mode, VREF = 1.65 V
–1
0
1
LSB
—
0.004
—
LSB/°C
–0.07
–0.02
0.02
%
TCOFF
EM
12 Bit Mode
Dynamic Performance 10 kHz Sine Wave Input 1dB below full scale, Max throughput, using AGND pin
Signal-to-Noise
Signal-to-Noise Plus Distortion
Total Harmonic Distortion
(Up to 5th Harmonic)
Spurious-Free Dynamic
Range
SNR
SNDR
THD
SFDR
12 Bit Mode
TBD
66
—
dB
10 Bit Mode
TBD
60
—
dB
12 Bit Mode
TBD
66
—
dB
10 Bit Mode
TBD
60
—
dB
12 Bit Mode
—
71
—
dB
10 Bit Mode
—
70
—
dB
12 Bit Mode
—
–79
—
dB
10 Bit Mode
—
–74
—
dB
*Note: Absolute input pin voltage is limited by the VDD supply.
Preliminary Rev 0.6
13
Electrical Specifications
C8051F85x/86x
Electrical Specifications
C8051F85x/86x
Table 1.8. Voltage Reference
Parameter
Symbol
Test Condition
Min
Typ
Max
Unit
VREFFS
1.65 V Setting
1.62
1.65
1.68
V
2.4 V Setting
2.35
2.4
2.45
V
TCREFFS
—
50
—
ppm/°C
tREFFS
—
—
1.5
µs
PSRRREFFS
—
400
—
ppm/V
—
5
—
µA
Internal Fast Settling Reference
Output Voltage
(Full Temperature and Supply
Range)
Temperature Coefficient
Turn-on Time
Power Supply Rejection
External Reference
Input Current
Sample Rate = 800 ksps;
VREF = 3.0 V
IEXTREF
Table 1.9. Temperature Sensor
Parameter
Symbol
Test Condition
Min
Typ
Max
Unit
Offset
VOFF
TA = 0 °C
—
757
—
mV
Offset Error*
EOFF
TA = 0 °C
—
TBD
—
mV
Slope
M
—
2.85
—
mV/°C
Slope Error*
EM
—
TBD
—
µV/°C
Linearity
—
0.5
—
°C
Turn-on Time
—
1.8
—
µs
*Note: Represents one standard deviation from the mean.
14
Preliminary Rev 0.6
Table 1.10. Comparators
Parameter
Symbol
Test Condition
Min
Typ
Max
Unit
Response Time, CPnMD = 00
(Highest Speed)
tRESP0
+100 mV Differential
—
100
—
ns
–100 mV Differential
—
150
—
ns
Response Time, CPnMD = 11
(Lowest Power)
tRESP3
+100 mV Differential
—
1.5
—
µs
–100 mV Differential
—
3.5
—
µs
CPnHYP = 00
—
0.4
—
mV
CPnHYP = 01
—
8
—
mV
CPnHYP = 10
—
16
—
mV
CPnHYP = 11
—
32
—
mV
CPnHYN = 00
—
-0.4
—
mV
CPnHYN = 01
—
–8
—
mV
CPnHYN = 10
—
–16
—
mV
CPnHYN = 11
—
–32
—
mV
CPnHYP = 00
—
0.5
—
mV
CPnHYP = 01
—
6
—
mV
CPnHYP = 10
—
12
—
mV
CPnHYP = 11
—
24
—
mV
CPnHYN = 00
—
-0.5
—
mV
CPnHYN = 01
—
–6
—
mV
CPnHYN = 10
—
–12
—
mV
CPnHYN = 11
—
–24
—
mV
CPnHYP = 00
—
0.7
—
mV
CPnHYP = 01
—
4.5
—
mV
CPnHYP = 10
—
9
—
mV
CPnHYP = 11
—
18
—
mV
CPnHYN = 00
—
-0.6
—
mV
CPnHYN = 01
—
–4.5
—
mV
CPnHYN = 10
—
–9
—
mV
CPnHYN = 11
—
–18
—
mV
Positive Hysterisis
Mode 0 (CPnMD = 00)
Negative Hysterisis
Mode 0 (CPnMD = 00)
Positive Hysterisis
Mode 1 (CPnMD = 01)
Negative Hysterisis
Mode 1 (CPnMD = 01)
Positive Hysterisis
Mode 2 (CPnMD = 10)
Negative Hysterisis
Mode 2 (CPnMD = 10)
HYSCP+
HYSCP-
HYSCP+
HYSCP-
HYSCP+
HYSCP-
Preliminary Rev 0.6
15
Electrical Specifications
C8051F85x/86x
Electrical Specifications
C8051F85x/86x
Table 1.10. Comparators
Parameter
Positive Hysterisis
Mode 3 (CPnMD = 11)
Negative Hysterisis
Mode 3 (CPnMD = 11)
Symbol
Test Condition
Min
Typ
Max
Unit
HYSCP+
CPnHYP = 00
—
1.5
—
mV
CPnHYP = 01
—
4
—
mV
CPnHYP = 10
—
8
—
mV
CPnHYP = 11
—
16
—
mV
CPnHYN = 00
—
-1.5
—
mV
CPnHYN = 01
—
–4
—
mV
CPnHYN = 10
—
–8
—
mV
CPnHYN = 11
—
–16
—
mV
HYSCP-
Input Range (CP+ or CP–)
VIN
-0.25
—
VDD+0.2
5
V
Input Pin Capacitance
CCP
—
7.5
—
pF
Common-Mode Rejection Ratio
CMRRCP
—
70
—
dB
Power Supply Rejection Ratio
PSRRCP
—
72
—
dB
-10
0
10
mV
—
3.5
—
µV/°C
Input Offset Voltage
VOFF
Input Offset Tempco
TCOFF
TA = 25 °C
Table 1.11. Port I/O
Parameter
Symbol
Test Condition
Min
Typ
Max
Unit
Output High Voltage (High Drive)
VOH
IOH = –3 mA
VDD – 0.7
—
—
V
Output Low Voltage (High Drive)
VOL
IOL = 8.5 mA
—
—
0.6
V
Output High Voltage (Low Drive)
VOH
IOH = –1 mA
VDD – 0.7
—
—
V
Output Low Voltage (Low Drive)
VOL
IOL = 1.4 mA
—
—
0.6
V
Input High Voltage
VIH
VDD – 0.6
—
—
V
Input Low Voltage
VIL
—
—
0.6
V
Pin Capacitance
CIO
—
7
—
pF
Weak Pull-Up Current
(VIN = 0 V)
IPU
VDD = 3.6
–30
–20
–10
µA
Input Leakage 
(Pullups off or Analog)
ILK
GND < VIN < VDD
–1
—
1
µA
Input Leakage Current with VIN
above VDD
ILK
VDD < VIN < VDD+2.0 V
0
5
150
µA
16
Preliminary Rev 0.6
1.2. Typical Power Curves
1.2.1. Operating Supply Current
5
NormalMode
4.5
IdleMode
SupplyCurrent(mA)
4
3.5
3
2.5
2
1.5
1
0.5
0
0
5
10
15
20
25
OperatingFrequency(MHz)
Figure 1.1. Typical Operating Current Running From 24.5 MHz Internal Oscillator
260
NormalMode
240
IdleMode
SupplyCurrent(μA)
220
200
180
160
140
120
100
10
20
30
40
50
60
70
80
OperatingFrequency(kHz)
Figure 1.2. Typical Operating Current Running From 80 kHz Internal Oscillator
Preliminary Rev 0.6
17
Electrical Specifications
C8051F85x/86x
1.2.2. ADC Supply Current
10ͲbitBurstMode,SingleConversions
12ͲbitBurstMode,SingleConversions
1200
1200
InternalReference,NormalBias
1100
InternalReference,LPBias
1000
OtherReference
900
OtherReference
900
SupplyCurrent(μA)
SupplyCurrent(μA)
InternalReference,NormalBias
1100
InternalReference,LPBias
1000
800
700
600
500
400
800
700
600
500
400
300
300
200
200
100
100
0
0
0
50
100
150
200
250
300
0
20
SampleRate(ksps)
40
60
80
100
120
SampleRate(ksps)
Figure 1.3. Typical ADC and Internal Reference Power Consumption in Burst Mode
10ͲbitConversions,NormalBias
10ͲbitConversions,LowPowerBias
950
450
Vdd=3.6V
Vdd=3.0V
430
Vdd=2.2V
SupplyCurrent(μA)
SupplyCurrent(μA)
Vdd=3.6V
440
Vdd=3.0V
900
850
800
750
Vdd=2.2V
420
410
400
390
380
370
700
360
650
350
100
200
300
400
500
600
700
800
50
150
SampleRate(ksps)
250
SampleRate(ksps)
12ͲbitConversions,NormalBias
12ͲbitConversions,LowPowerBias
950
450
Vdd=3.6V
Vdd=3.6V
440
Vdd=3.0V
900
Vdd=3.0V
430
Vdd=2.2V
SupplyCurrent(μA)
SupplyCurrent(μA)
Electrical Specifications
C8051F85x/86x
850
800
750
Vdd=2.2V
420
410
400
390
380
370
700
360
650
350
25
50
75
100
125
150
175
200
10
SampleRate(ksps)
20
30
40
50
SampleRate(ksps)
Figure 1.4. Typical ADC Power Consumption in Normal (Always-On) Mode
18
Preliminary Rev 0.6
60
1.3. Thermal Conditions
Table 1.12. Thermal Conditions
Parameter
Symbol
Test Condition
Min
Typ
Max
Unit
JA
SOIC-16 Packages
—
TBD
—
°C/W
QFN-20 Packages
—
TBD
—
°C/W
QSOP-24 Packages
—
TBD
—
°C/W
Thermal Resistance*
*Note: Thermal resistance assumes a multi-layer PCB with any exposed pad soldered to a PCB pad.
1.4. Absolute Maximum Ratings
Stresses above those listed under Table 1.13 may cause permanent damage to the device. This is a stress rating
only and functional operation of the devices at those or any other conditions above those indicated in the operation
listings of this specification is not implied. Exposure to maximum rating conditions for extended periods may affect
device reliability.
Table 1.13. Absolute Maximum Ratings
Parameter
Symbol
Test Condition
Min
Typ
Max
Ambient Temperature Under Bias
TBIAS
–55
125
°C
Storage Temperature
TSTG
–65
150
°C
Voltage on VDD
VDD
GND–0.3
4.2
V
Voltage on I/O pins or RST
VIN
VDD > 3.3 V
GND–0.3
5.8
V
VDD < 3.3 V
GND–0.3
VDD+2.5
V
Total Current Sunk into Supply Pin
IVDD
—
400
mA
Total Current Sourced out of Ground
Pin
IGND
400
—
mA
Current Sourced or Sunk by Any I/O Pin
or RST
IPIO
-100
100
mA
Power Dissipation at TA = 125 °C
PD
SOIC-16 Packages
—
TBD
mW
QFN-20 Packages
—
TBD
mW
QSOP-24 Packages
—
TBD
mW
Preliminary Rev 0.6
19
Electrical Specifications
C8051F85x/86x
System Overview
C8051F85x/86x
2. System Overview
The C8051F85x/86x device family are fully integrated, mixed-signal system-on-a-chip MCUs. Highlighted features
are listed below. Refer to Table 4.1 for specific product feature selection and part ordering numbers.
Core:
Pipelined
CIP-51 Core
compatible with standard 8051 instruction set
70% of instructions execute in 1-2 clock cycles
25 MHz maximum operating frequency
Fully
Memory:
2-8
512
Power:
kB flash; in-system programmable in 512-byte sectors
bytes RAM (including 256 bytes standard 8051 RAM and 256 bytes on-chip XRAM)
Internal
low drop-out (LDO) regulator for CPU core voltage
reset circuit and brownout detectors
Power-on
I/O:
Up to 18 total multifunction I/O pins:
All
pins 5 V tolerant under bias
peripheral crossbar for peripheral routing
5 mA source, 12.5 mA sink allows direct drive of LEDs
Flexible
Clock
Sources:
Low-power
internal oscillator: 24.5 MHz ±2%
internal oscillator: 80 kHz
External CMOS clock option
Low-frequency
Timers/Counters
and PWM:
3-channel
Programmable Counter Array (PCA) supporting PWM, capture/compare and frequency output modes
16-bit general-purpose timers
Independent watchdog timer, clocked from low frequency oscillator
4x
Communications
and Other Digital Peripherals:
UART
SPI™
I
2C
/ SMBus™
CRC Unit, supporting automatic CRC of flash at 256-byte boundaries
16-bit
Analog:
12-Bit
2
Analog-to-Digital Converter (ADC)
x Low-Current Comparators
On-Chip Debugging
With on-chip power-on reset, voltage supply monitor, watchdog timer, and clock oscillator, the C8051F85x/86x
devices are truly standalone system-on-a-chip solutions. The flash memory is reprogrammable in-circuit, providing
non-volatile data storage and allowing field upgrades of the firmware.
The on-chip debugging interface (C2) allows non-intrusive (uses no on-chip resources), full speed, in-circuit
debugging using the production MCU installed in the final application. This debug logic supports inspection and
modification of memory and registers, setting breakpoints, single stepping, and run and halt commands. All analog
and digital peripherals are fully functional while debugging.
Each device is specified for 2.2 to 3.6 V operation, and are available in 20-pin QFN, 16-pin SOIC or 24-pin QSOP
packages. All package options are lead-free and RoHS compliant. The device is available in two temperature
grades: -40 to +85 °C or –40 to +125 °C. See Table 4.1 for ordering information. A block diagram is included in
Figure 2.1.
20
Preliminary Rev 0.6
Power On
Reset
Reset
C2CK/RST
Debug /
Programming
Hardware
C2D
Port I/O Configuration
CIP-51 8051
Controller Core
Port 0
Drivers
P0.0/VREF
P0.1/AGND
P0.2
P0.3/EXTCLK
P0.4/TX
P0.5/RX
P0.6/CNVSTR
P0.7
Port 1
Drivers
P1.0
P1.1
P1.2
P1.3
P1.4
P1.5
P1.6
P1.7
Port 2
Driver
P2.0/C2D
P2.1
Digital Peripherals
8k Byte ISP Flash
Program Memory
UART
256 Byte SRAM
Timers 0,
1, 2, 3
Priority
Crossbar
Decoder
3-ch PCA
I2C /
SMBus
256 Byte XRAM
SPI
VDD
Power Net
GND
CRC
Independent
Watchdog Timer
SYSCLK
24.5 MHz
2%
Oscillator
Low-Freq.
Oscillator
EXTCLK
SFR
Bus
Crossbar Control
Analog Peripherals
Internal
Reference
VDD
12/10 bit
ADC
CMOS
Oscillator
Input
VREF
A
M
U
X
VDD
Temp
Sensor
+
-+
2 Comparators
System Clock
Configuration
Figure 2.1. C8051F85x/86x Family Block Diagram (QSOP-24 Shown)
Preliminary Rev 0.6
21
System Overview
C8051F85x/86x
System Overview
C8051F85x/86x
2.1. Power
2.1.1. LDO
The C8051F85x/86x devices include an internal regulator to regulate the supply voltage down the core operating
voltage of 1.8 V. This LDO consumes little power, but can be shut down in the power-saving Stop mode.
2.1.2. Voltage Supply Monitor (VMON0)
The C8051F85x/86x devices include a voltage supply monitor which allows devices to function in known, safe
operating condition without the need for external hardware.
The supply monitor module includes the following features:
Holds
the device in reset if the main VDD supply drops below the VDD Reset threshold.
2.1.3. Device Power Modes
The C8051F85x/86x devices feature three low power modes in addition to normal operating mode, allowing the
designer to save power when the core is not in use. All power modes are detailed in Table 2.1.
Table 2.1. C8051F85x/86x Power Modes
Mode
Description
Normal
Core and peripherals operating
at full speed
Idle
Core
halted
Peripherals operate at
full speed
clocks stopped
LDO and
(optionally)
comparators still
running
Pins retain state
Mode Entrance
Mode Exit
Set IDLE bit in PCON
Any enabled interrupt or
reset source
Clear STOPCF in REG0MD
and
Set STOP bit in PCON
Device reset
Set STOPCF in REG0MD
and
Set STOP bit in PCON
Device reset
All
Core
Stop
All
Shutdown
clocks stopped
LDO and all
analog circuits shut
down
Pins retain state
Core
In addition, the user may choose to lower the clock speed in Normal and Idle modes to save power when the CPU
requirements allow for lower speed.
22
Preliminary Rev 0.6
2.1.3.1. Normal Mode
Normal mode encompasses the typical full-speed operation. The power consumption of the device in this mode will
vary depending on the system clock speed and any analog peripherals that are enabled.
2.1.3.2. Idle Mode
Setting the IDLE bit in PCON 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 bit 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.
2.1.3.3. Stop Mode (Regulator On)
Setting the STOP bit in PCON when STOPCF in REG0CN is clear 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. Each analog peripheral may be shut down individually prior to entering stop mode.
Stop mode can only be terminated by an internal or external reset.
2.1.3.4. Shutdown Mode (Regulator Off)
Shutdown mode is an extension of the normal stop mode operation. Setting the STOP bit in PCON when STOPCF
in REG0CN is also set causes the controller core to enter shutdown mode as soon as the instruction that sets the
bit completes execution, and then the internal regulator is powered down. In shutdown mode, all core functions,
memories and peripherals are powered off. An external pin reset or power-on reset is required to exit shutdown
mode.
2.2. I/O
2.2.1. General Features
The C8051F85x/86x ports have the following features:
Push-pull
or open-drain output modes and analog or digital modes.
Match allows the device to recognize a change on a port pin value and wake from idle mode or
generate an interrupt.
Internal pull-up resistors can be globally enabled or disabled.
Two external interrupts provide unique interrupt vectors for monitoring time-critical events.
Above-rail tolerance allows 5 V interface when device is powered.
Port
2.2.2. Crossbar
The C8051F85x/86x devices have a digital peripheral crossbar with the following features:
Flexible
peripheral assignment to port pins.
can be individually skipped to move peripherals as needed for design or layout considerations.
The crossbar has a fixed priority for each I/O function and assigns these functions to the port pins. When a digital
resource is selected, the least-significant unassigned port pin is assigned to that resource. If a port pin is assigned,
the crossbar skips that pin when assigning the next selected resource. Additionally, the crossbar will skip port pins
whose associated bits in the PnSKIP registers are set. This provides some flexibility when designing a system: pins
involved with sensitive analog measurements can be moved away from digital I/O and peripherals can be moved
around the chip as needed to ease layout constraints.
Pins
Preliminary Rev 0.6
23
System Overview
C8051F85x/86x
System Overview
C8051F85x/86x
2.3. Clocking
The C8051F85x/86x devices have two internal oscillators and the option to use an external CMOS input at a pin as
the system clock. A programmable divider allows the user to internally run the system clock at a slower rate than
the selected oscillator if desired.
2.4. Counters/Timers and PWM
2.4.1. Programmable Counter Array (PCA0)
The C8051F85x/86x devices include a three-channel, 16-bit Programmable Counter Array with the following
features:
16-bit
time base.
Programmable clock divisor and clock source selection.
Three independently-configurable channels.
8, 9, 10, 11 and 16-bit PWM modes (center or edge-aligned operation).
Output polarity control.
Frequency output mode.
Capture on rising, falling or any edge.
Compare function for arbitrary waveform generation.
Software timer (internal compare) mode.
Can accept hardware “kill” signal from comparator 0.
2.4.2. Timers (Timer 0, Timer 1, Timer 2 and Timer 3)
Timers include the following features:
Timer
0 and Timer 1 are standard 8051 timers, supporting backwards-compatibility with firmware and
hardware.
Timer 2 and Timer 3 can each operate as 16-bit auto-reload or two independent 8-bit auto-reload timers,
and include pin or LFO clock capture capabilities.
2.4.3. Watchdog Timer (WDT0)
The watchdog timer includes a 16-bit timer with a programmable reset period. The registers are protected from
inadvertent access by an independent lock and key interface.
The Watchdog Timer has the following features:
Programmable
timeout interval.
Runs from the low frequency oscillator.
Lock-out feature to prevent any modification until a system reset.
24
Preliminary Rev 0.6
2.5. Communications and other Digital Peripherals
2.5.1. Universal Asynchronous Receiver/Transmitter (UART0)
The UART uses two signals (TX and RX) and a predetermined fixed baud rate to provide asynchronous
communications with other devices.
The UART module provides the following features:
Asynchronous
transmissions and receptions.
rates up to SYSCLK / 2 (transmit) or SYSCLK / 8 (receive).
8 or 9 bit data.
Automatic start and stop generation.
Baud
2.5.2. Serial Peripheral Interface (SPI0)
SPI is a 3- or 4-wire communication interface that includes a clock, input data, output data, and an optional select
signal.
The SPI module includes the following features:
Supports
3- or 4-wire master or slave modes.
Supports external clock frequencies up to SYSCLK / 2 in master mode and SYSCLK / 10 in slave mode.
Support for all clock phase and polarity modes.
8-bit programmable clock rate.
Support for multiple masters on the same data lines.
2.5.3. System Management Bus / I2C (SMBus0)
The SMBus interface is a two-wire, bi-directional serial bus compatible with both I2C and SMBus protocols. The
two clock and data signals operate in open-drain mode with external pull-ups to support automatic bus arbitration.
Reads and writes to the interface are byte oriented with the SMBus interface autonomously controlling the serial
transfer of the data. Data can be transferred at up to 1/8th of the system clock as a master or slave, which can be
faster than allowed by the SMBus / I2C specification, depending on the clock source 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 may operate as a master and/or slave, and may function on a bus with multiple masters. The
SMBus provides control of SDA (serial data), SCL (serial clock) generation and synchronization, arbitration logic,
and start/stop control and generation.
The SMBus module includes the following features:
Standard
(up to 100 kbps) and Fast (400 kbps) transfer speeds.
for master, slave, and multi-master modes.
Hardware synchronization and arbitration for multi-master mode.
Clock low extending (clock stretching) to interface with faster masters.
Hardware support for 7-bit slave and general call address recognition.
Firmware support for 10-bit slave address decoding.
Ability to inhibit all slave states.
Programmable data setup/hold times.
Support
2.5.4. 16/32-bit CRC (CRC0)
The CRC module is designed to provide hardware calculations for flash memory verification and communications
protocols. The CRC module supports the standard CCITT-16 16-bit polynomial (0x1021), and includes the
following features:
Support
for four CCITT-16 polynomial.
bit reversal.
Automatic CRC of flash contents on one or more 256-byte blocks.
Initial seed selection of 0x0000 or 0xFFFF.
Byte-level
Preliminary Rev 0.6
25
System Overview
C8051F85x/86x
System Overview
C8051F85x/86x
2.6. Analog Peripherals
2.6.1. 12-Bit Analog-to-Digital Converter (ADC0)
The ADC0 module on C8051F85x/86x devices is a Successive Approximation Register (SAR) Analog to Digital
Converter (ADC). The key features of the ADC module are:
Single-ended
12-bit and 10-bit modes.
Supports an output update rate of 200 ksps samples per second in 12-bit mode or 800 ksps samples per
second in 10-bit mode.
Operation in low power modes at lower conversion speeds.
Selectable asynchronous hardware conversion trigger
Output data window comparator allows automatic range checking.
Support for Burst Mode, which produces one set of accumulated data per conversion-start trigger with
programmable power-on settling and tracking time.
Conversion complete and window compare interrupts supported.
Flexible output data formatting.
Includes an internal fast-settling reference with two levels (1.65 V and 2.4 V) and support for external
reference and signal ground.
2.6.2. Low Current Comparators (CMP0, CMP1)
The comparators take two analog input voltages and output the relationship between these voltages (less than or
greater than) as a digital signal. The Low Power Comparator module includes the following features:
Multiple
sources for the positive and negative poles, including VDD, VREF, and I/O pins.
Two outputs are available: a digital synchronous latched output and a digital asynchronous raw output.
Programmable hysteresis and response time.
Falling or rising edge interrupt options on the comparator output.
Provide “kill” signal to PCA module.
Comparator 0 can be used to reset the device.
26
Preliminary Rev 0.6
2.7. 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:
The
core halts program execution.
Module registers are initialized to their defined reset values unless the bits reset only with a power-on
reset.
External port pins are forced to a known state.
Interrupts and timers are disabled.
All registers are reset to the predefined values noted in the register descriptions unless the bits only reset with a
power-on reset. The contents of RAM are unaffected during a reset; any previously stored data is preserved as
long as power is not lost.
The Port I/O latches are reset to 1 in open-drain mode. Weak pullups are enabled during and after the reset. For
VDD Supply Monitor and power-on resets, the RST pin is driven low until the device exits the reset state.
On exit from the reset state, the program counter (PC) is reset, and the system clock defaults to the internal lowpower oscillator. The Watchdog Timer is enabled with the Low Frequency Oscillator (LFO0) as its clock source.
Program execution begins at location 0x0000.
2.8. On-Chip Debugging
The C8051F85x/86x devices include an on-chip Silicon Labs 2-Wire (C2) debug interface to allow flash programming and in-system debugging with the production part installed in the end application. The C2 interface uses a
clock signal (C2CK) and a bi-directional C2 data signal (C2D) to transfer information between the device and a
host system. See the C2 Interface Specification for details on the C2 protocol.
Preliminary Rev 0.6
27
System Overview
C8051F85x/86x
3. Pin Definitions
3.1. C8051F850/1/2/3/4/5 QSOP24 Pin Definitions
N/C
1
24
N/C
P0.2
2
23
P0.3
P0.1 / AGND
3
22
P0.4
P0.0 / VREF
4
21
P0.5
GND
5
20
P0.6
VDD
6
19
P0.7
RST / C2CK
7
18
P1.0
C2D / P2.0
8
17
P1.1
P1.7
9
16
P1.2
P1.6
10
15
P1.3
P1.5
11
14
P1.4
P2.1
12
13
N/C
24 pin QSOP
(Top View)
Figure 3.1. C8051F851/2/3/4/5/6-GU and C8051F851/2/3/4/5/6-IU Pinout
28
Type
GND
Ground
5
VDD
Power
6
RST /
C2CK
Active-low Reset /
C2 Debug Clock
7
P0.0
Standard I/O
4
Preliminary Rev 0.6
Yes
P0MAT.0
INT0.0
INT1.0
Analog Functions
Pin Name
Additional Digital Functions
Crossbar Capability
Table 3.1. Pin Definitions for C8051F851/2/3/4/5/6-GU and C8051F851/2/3/4/5/6-IU
Pin Numbers
Pin Definitions
C8051F85x/86x
ADC0.0
CP0P.0
CP0N.0
VREF
Analog Functions
Additional Digital Functions
Pin Numbers
Crossbar Capability
Table 3.1. Pin Definitions for C8051F851/2/3/4/5/6-GU and C8051F851/2/3/4/5/6-IU
Pin Name
Type
P0.1
Standard I/O
3
Yes
P0MAT.1
INT0.1
INT1.1
ADC0.1
CP0P.1
CP0N.1
AGND
P0.2
Standard I/O
2
Yes
P0MAT.2
INT0.2
INT1.2
ADC0.2
CP0P.2
CP0N.2
P0.3 /
EXTCLK
Standard I/O /
External CMOS Clock Input
23
Yes
P0MAT.3
EXTCLK
INT0.3
INT1.3
ADC0.3
CP0P.3
CP0N.3
P0.4
Standard I/O
22
Yes
P0MAT.4
INT0.4
INT1.4
ADC0.4
CP0P.4
CP0N.4
P0.5
Standard I/O
21
Yes
P0MAT.5
INT0.5
INT1.5
ADC0.5
CP0P.5
CP0N.5
P0.6
Standard I/O
20
Yes
P0MAT.6
CNVSTR
INT0.6
INT1.6
ADC0.6
CP0P.6
CP0N.6
P0.7
Standard I/O
19
Yes
P0MAT.7
INT0.7
INT1.7
ADC0.7
CP0P.7
CP0N.7
P1.0
Standard I/O
18
Yes
P1MAT.0
ADC0.8
CP1P.0
CP1N.0
P1.1
Standard I/O
17
Yes
P1MAT.1
ADC0.9
CP1P.1
CP1N.1
Preliminary Rev 0.6
29
Pin Definitions
C8051F85x/86x
30
Analog Functions
Additional Digital Functions
Crossbar Capability
Table 3.1. Pin Definitions for C8051F851/2/3/4/5/6-GU and C8051F851/2/3/4/5/6-IU
Pin Numbers
Pin Definitions
C8051F85x/86x
Pin Name
Type
P1.2
Standard I/O
16
Yes
P1MAT.2
ADC0.10
CP1P.2
CP1N.2
P1.3
Standard I/O
15
Yes
P1MAT.3
ADC0.11
CP1P.3
CP1N.3
P1.4
Standard I/O
14
Yes
P1MAT.4
ADC0.12
CP1P.4
CP1N.4
P1.5
Standard I/O
11
Yes
P1MAT.5
ADC0.13
CP1P.5
CP1N.5
P1.6
Standard I/O
10
Yes
P1MAT.6
ADC0.14
CP1P.6
CP1N.6
P1.7
Standard I/O
9
Yes
P2.0 /
C2D
Standard I/O /
C2 Debug Data
8
P2.1
Standard I/O
12
N/C
No Connection
1
13
24
Preliminary Rev 0.6
ADC0.15
CP1P.7
CP1N.7
RST / C2CK
5
P0.5
17
P0.4
18
P0.3
GND
6
P1.6
C2D / P2.0
(Top View)
15
P0.7
14
P1.0
13
P1.1
12
GND
11
10
4
P0.6
P1.2
P1.3
VDD
16
20 pin QFN
9
3
P1.4
GND
8
2
P1.5
P0.0 / VREF
20
1
7
P0.1 / AGND
19
P0.2
3.2. C8051F850/1/2/3/4/5 QFN20 Pin Definitions
Figure 3.2. C8051F851/2/3/4/5/6-GM and C8051F851/2/3/4/5/6-IM Pinout
Type
GND
Ground
Center
3
12
VDD
Power
4
RST /
C2CK
Active-low Reset /
C2 Debug Clock
5
Preliminary Rev 0.6
Analog Functions
Pin Name
Additional Digital Functions
Pin Numbers
Crossbar Capability
Table 3.2. Pin Definitions for C8051F851/2/3/4/5/6-GM and C8051F851/2/3/4/5/6-IM
31
Pin Definitions
C8051F85x/86x
32
Analog Functions
Additional Digital Functions
Crossbar Capability
Table 3.2. Pin Definitions for C8051F851/2/3/4/5/6-GM and C8051F851/2/3/4/5/6-IM
Pin Numbers
Pin Definitions
C8051F85x/86x
Pin Name
Type
P0.0
Standard I/O
2
Yes
P0MAT.0
INT0.0
INT1.0
ADC0.0
CP0P.0
CP0N.0
VREF
P0.1
Standard I/O
1
Yes
P0MAT.1
INT0.1
INT1.1
ADC0.1
CP0P.1
CP0N.1
AGND
P0.2
Standard I/O
20
Yes
P0MAT.2
INT0.2
INT1.2
ADC0.2
CP0P.2
CP0N.2
P0.3
Standard I/O
19
Yes
P0MAT.3
EXTCLK
INT0.3
INT1.3
ADC0.3
CP0P.3
CP0N.3
P0.4
Standard I/O
18
Yes
P0MAT.4
INT0.4
INT1.4
ADC0.4
CP0P.4
CP0N.4
P0.5
Standard I/O
17
Yes
P0MAT.5
INT0.5
INT1.5
ADC0.5
CP0P.5
CP0N.5
P0.6
Standard I/O
16
Yes
P0MAT.6
CNVSTR
INT0.6
INT1.6
ADC0.6
CP0P.6
CP0N.6
P0.7
Standard I/O
15
Yes
P0MAT.7
INT0.7
INT1.7
ADC0.7
CP0P.7
CP0N.7
Preliminary Rev 0.6
Analog Functions
Additional Digital Functions
Pin Numbers
Crossbar Capability
Table 3.2. Pin Definitions for C8051F851/2/3/4/5/6-GM and C8051F851/2/3/4/5/6-IM
Pin Name
Type
P1.0
Standard I/O
14
Yes
P1MAT.0
ADC0.8
CP1P.0
CP1N.0
P1.1
Standard I/O
13
Yes
P1MAT.1
ADC0.9
CP1P.1
CP1N.1
P1.2
Standard I/O
11
Yes
P1MAT.2
ADC0.10
CP1P.2
CP1N.2
P1.3
Standard I/O
10
Yes
P1MAT.3
ADC0.11
CP1P.3
CP1N.3
P1.4
Standard I/O
9
Yes
P1MAT.4
ADC0.12
CP1P.4
CP1N.4
P1.5
Standard I/O
8
Yes
P1MAT.5
ADC0.13
CP1P.5
CP1N.5
P1.6
Standard I/O
7
Yes
P1MAT.6
ADC0.14
CP1P.6
CP1N.6
P2.0 /
C2D
Standard I/O /
C2 Debug Data
6
Preliminary Rev 0.6
33
Pin Definitions
C8051F85x/86x
3.3. C8051F860/1/2/3/4/5 SOIC16 Pin Definitions
P0.2
1
16
P0.3
P0.1 / AGND
2
15
P0.4
P0.0 / VREF
3
14
P0.5
GND
4
13
P0.6
VDD
5
12
P0.7
RST / C2CK
6
11
P1.0
C2D / P2.0
7
10
P1.1
P1.3
8
9
P1.2
16 pin SOIC
(Top View)
Figure 3.3. C8051F861/2/3/4/5/6-GS and C8051F861/2/3/4/5/6-IS Pinout
34
Analog Functions
Additional Digital Functions
Crossbar Capability
Table 3.3. Pin Definitions for C8051F861/2/3/4/5/6-GS and C8051F861/2/3/4/5/6-IS
Pin Numbers
Pin Definitions
C8051F85x/86x
Pin Name
Type
GND
Ground
4
VDD
Power
5
RST /
C2CK
Active-low Reset /
C2 Debug Clock
6
P0.0
Standard I/O
3
Yes
P0MAT.0
INT0.0
INT1.0
ADC0.0
CP0P.0
CP0N.0
P0.1
Standard I/O
2
Yes
P0MAT.1
INT0.1
INT1.1
ADC0.1
CP0P.1
CP0N.1
Preliminary Rev 0.6
Analog Functions
Additional Digital Functions
Pin Numbers
Crossbar Capability
Table 3.3. Pin Definitions for C8051F861/2/3/4/5/6-GS and C8051F861/2/3/4/5/6-IS
Pin Name
Type
P0.2
Standard I/O
1
Yes
P0MAT.2
INT0.2
INT1.2
ADC0.2
CP0P.2
CP0N.2
P0.3 /
EXTCLK
Standard I/O /
External CMOS Clock Input
16
Yes
P0MAT.3
EXTCLK
INT0.3
INT1.3
ADC0.3
CP0P.3
CP0N.3
P0.4
Standard I/O
15
Yes
P0MAT.4
INT0.4
INT1.4
ADC0.4
CP0P.4
CP0N.4
P0.5
Standard I/O
14
Yes
P0MAT.5
INT0.5
INT1.5
ADC0.5
CP0P.5
CP0N.5
P0.6
Standard I/O
13
Yes
P0MAT.6
CNVSTR
INT0.6
INT1.6
ADC0.6
CP1P.0
CP1N.0
P0.7
Standard I/O
12
Yes
P0MAT.7
INT0.7
INT1.7
ADC0.7
CP1P.1
CP1N.1
P1.0
Standard I/O
11
Yes
P1MAT.0
ADC0.8
CP1P.2
CP1N.2
P1.1
Standard I/O
10
Yes
P1MAT.1
ADC0.9
CP1P.3
CP1N.3
P1.2
Standard I/O
9
Yes
P1MAT.2
ADC0.10
CP1P.4
CP1N.4
Preliminary Rev 0.6
35
Pin Definitions
C8051F85x/86x
36
Type
P1.3
Standard I/O
8
P2.0 /
C2D
Standard I/O /
C2 Debug Data
7
Preliminary Rev 0.6
Yes
P1MAT.3
Analog Functions
Pin Name
Additional Digital Functions
Crossbar Capability
Table 3.3. Pin Definitions for C8051F861/2/3/4/5/6-GS and C8051F861/2/3/4/5/6-IS
Pin Numbers
Pin Definitions
C8051F85x/86x
ADC0.11
CP1P.5
CP1N.5
4. Ordering Information
C8051 F 850 – B – G M
Package Type M (QFN), U (QSOP), S (SSOP)
Temperature Grade G (-40 to +85), I (-40 to +125)
Revision
Family and Features – 85x and 86x
Memory Type – F (Flash)
Silicon Labs 8051 Family
Figure 4.1. C8051F85x/86x Part Numbering
All C8051F85x/86x family members have the following features:
CIP-51
Core running up to 25 MHz
Internal Oscillators (24.5 MHz and 80 kHz)
I2C/SMBus
SPI
UART
3-Channel Programmable Counter Array (PWM, Clock Generation, Capture/Compare)
4 16-bit Timers
2 Analog Comparators
16-bit CRC Unit
In addition to these features, each part number in the C8051F85x/86x family has a set of features that vary across
the product line. The product selection guide in Table 4.1 shows the features available on each family member.
Two
Preliminary Rev 0.6
37
Ordering Information
C8051F85x/86x
Digital Port I/Os (Total)
Number of ADC0 Channels
I/O with Comparator 0/1 Inputs
Pb-free (RoHS Compliant)
AEC-Q100 Qualified
8
512
16
15
15


-40 to 85 °C
QFN-20
C8051F850-B-GU
8
512
18
16
16


-40 to 85 °C
QSOP-24
C8051F851-B-GM
4
512
16
15
15


-40 to 85 °C
QFN-20
C8051F851-B-GU
4
512
18
16
16


-40 to 85 °C
QSOP-24
C8051F852-B-GM
2
256
16
15
15


-40 to 85 °C
QFN-20
C8051F852-B-GU
2
256
18
16
16


-40 to 85 °C
QSOP-24
C8051F853-B-GM
8
512
16
—
15


-40 to 85 °C
QFN-20
C8051F853-B-GU
8
512
18
—
16


-40 to 85 °C
QSOP-24
C8051F854-B-GM
4
512
16
—
15


-40 to 85 °C
QFN-20
C8051F854-B-GU
4
512
18
—
16


-40 to 85 °C
QSOP-24
C8051F855-B-GM
2
256
16
—
15


-40 to 85 °C
QFN-20
C8051F855-B-GU
2
256
18
—
16


-40 to 85 °C
QSOP-24
C8051F860-B-GS
8
512
13
12
12


-40 to 85 °C
SOIC-16
C8051F861-B-GS
4
512
13
12
12


-40 to 85 °C
SOIC-16
C8051F862-B-GS
2
256
13
12
12


-40 to 85 °C
SOIC-16
C8051F863-B-GS
8
512
13
—
12


-40 to 85 °C
SOIC-16
C8051F864-B-GS
4
512
13
—
12


-40 to 85 °C
SOIC-16
C8051F865-B-GS
2
256
13
—
12


-40 to 85 °C
SOIC-16
Package
RAM (Bytes)
C8051F850-B-GM
Temperature Range
Flash Memory (kB)
Table 4.1. Product Selection Guide
Ordering Part Number
Ordering Information
C8051F85x/86x
-IM, -IU and -IS extended temperature range devices (-40 to 125 °C) available in Q4 2013.
38
Preliminary Rev 0.6
5. QSOP-24 Package Specifications
Figure 5.1. QSOP-24 Package Drawing
Table 5.1. QSOP-24 Package Dimensions
Dimension
Min
Nom
Max
Dimension
Min
Nom
Max
A
—
—
1.75
e
A1
0.10
—
0.25
L
0.40
—
1.27
b
0.20
—
0.30

0º
—
8º
c
0.10
—
0.25
aaa
0.20
0.635 BSC
D
8.65 BSC
bbb
0.18
E
6.00 BSC
ccc
0.10
E1
3.90 BSC
ddd
0.10
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-137, variation AE.
4. Recommended card reflow profile is per the JEDEC/IPC J-STD-020 specification for Small Body
Components.
Preliminary Rev 0.6
39
QSOP-24 Package Specifications
C8051F85x/86x
QSOP-24 Package Specifications
C8051F85x/86x
Figure 5.2. QSOP-24 PCB Land Pattern
Table 5.2. QSOP-24 PCB Land Pattern Dimensions
Dimension
Min
C
E
X
Y
5.20
Max
5.30
0.635 BSC
0.30
1.50
0.40
1.60
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.
40
Preliminary Rev 0.6
6. QFN-20 Package Specifications
Figure 6.1. QFN-20 Package Drawing
Table 6.1. QFN-20 Package Dimensions
Symbol
Millimeters
Symbol
Millimeters
Min
Nom
Max
A
0.70
0.75
0.80
f
A1
0.00
0.02
0.05
L
0.3
0.40
0.5
b
0.20
0.25
0.30
L1
0.00
—
0.10
c
0.27
0.32
0.37
aaa
—
—
0.05
bbb
—
—
0.05
ccc
—
—
0.08
D
D2
3.00 BSC
1.6
1.70
1.8
Min
Nom
Max
2.53 BSC
e
0.50 BSC
ddd
—
—
0.10
E
3.00 BSC
eee
—
—
0.10
E2
1.6
1.70
1.8
Notes:
1. All dimensions are shown in millimeters unless otherwise noted.
2. Dimensioning and tolerancing per ANSI Y14.5M-1994.
Preliminary Rev 0.6
41
QFN-20 Package Specifications
C8051F85x/86x
QFN-20 Package Specifications
C8051F85x/86x
Figure 6.2. QFN-20 Landing Diagram
42
Preliminary Rev 0.6
Table 6.2. QFN-20 Landing Diagram Dimensions
Symbol
Millimeters
Min
D
D2
Symbol
Max
2.71 REF
1.60
1.80
Min
Max
GE
2.10
—
W
—
0.34
—
e
0.50 BSC
X
E
2.71 REF
Y
E2
f
GD
1.60
1.80
2.53 BSC
2.10
Millimeters
0.28
0.61 REF
ZE
—
3.31
ZD
—
3.31
—
Notes: General
1. All dimensions shown are in millimeters (mm) unless otherwise noted.
2. Dimensioning and Tolerancing is per the ANSI Y14.5M-1994 specification.
3. This Land Pattern Design is based on 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 0.05 mm.
Notes: Solder Mask Design
1. 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.
Notes: Stencil Design
1. A stainless steel, laser-cut and electro-polished stencil with trapezoidal walls should
be used to assure good solder paste release.
2. The stencil thickness should be 0.125 mm (5 mils).
3. The ratio of stencil aperture to land pad size should be 1:1 for the perimeter pads.
4. A 1.45 x 1.45 mm square aperture should be used for the center pad. This provides
approximately 70% solder paste coverage on the pad, which is optimum to assure
correct component stand-off. 
Notes: Card Assembly
1. A No-Clean, Type-3 solder paste is recommended.
2. The recommended card reflow profile is per the JEDEC/IPC J-STD-020 specification
for Small Body Components.
Preliminary Rev 0.6
43
QFN-20 Package Specifications
C8051F85x/86x
SOIC-16 Package Specifications
C8051F85x/86x
7. SOIC-16 Package Specifications
Figure 7.1. SOIC-16 Package Drawing
Table 7.1. SOIC-16 Package Dimensions
Dimension
Min
A
Nom
Max
Dimension
Min
Nom
Max
—
1.75
L
0.40
A1
0.10
0.25
L2
A2
1.25
—
h
0.25
0.50
b
0.31
0.51

0º
8º
c
0.17
0.25
aaa
0.10
1.27
0.25 BSC
D
9.90 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) unless otherwise noted.
2. Dimensioning and Tolerancing per ANSI Y14.5M-1994.
3. This drawing conforms to the JEDEC Solid State Outline MS-012, Variation AC.
4. Recommended card reflow profile is per the JEDEC/IPC J-STD-020 specification for Small Body
Components.
44
Preliminary Rev 0.6
Figure 7.2. SOIC-16 PCB Land Pattern
Table 7.2. SOIC-16 PCB Land Pattern Dimensions
Dimension
Feature
(mm)
C1
E
X1
Y1
Pad Column Spacing
Pad Row Pitch
Pad Width
Pad Length
5.40
1.27
0.60
1.55
Notes:
General
1. All dimensions shown are in millimeters (mm) unless otherwise noted.
2. This Land Pattern Design is based on IPC-7351 pattern SOIC127P600X165-16N for Density
Level B (Median Land Protrusion).
3. All feature sizes shown are at Maximum Material Condition (MMC) and a card fabrication
tolerance of 0.05 mm is assumed.
Preliminary Rev 0.6
45
SOIC-16 Package Specifications
C8051F85x/86x
Memory Organization
C8051F85x/86x
8. Memory Organization
The memory organization of the CIP-51 System Controller is similar to that of a standard 8051. There are two
separate memory spaces: program memory and data memory. Program and data memory share the same address
space but are accessed via different instruction types. The memory organization of the C8051F85x/86x device
family is shown in Figure 8.1.
PROGRAM/DATA MEMORY
(FLASH)
DATA MEMORY (RAM)
INTERNAL DATA ADDRESS SPACE
0xFF
0x1FFF
0x80
0x7F
Upper 128 RAM
(Indirect Addressing
Only)
Special Function
Registers
(Direct Addressing Only)
(Direct and Indirect Addressing)
0x30
0x2F
0x20
0x1F
8 kB FLASH
(In-System
Programmable in 512
Byte Sectors)
0x00
32 Bit-Addressable Bytes
Lower 128 RAM
(Direct and Indirect
Addressing)
32 General Purpose Registers
EXTERNAL DATA ADDRESS SPACE
0xFFFF
Same 256 bytes as 0x0000 to 0x00FF,
wrapped on 256-byte boundaries
0x0100
0x00FF
0x0000
0x0000
XRAM - 256 Bytes
(accessable using MOVX instruction)
Figure 8.1. C8051F85x/86x Memory Map (8 kB flash version shown)
46
Preliminary Rev 0.6
8.1. Program Memory
The CIP-51 core has a 64 kB program memory space. The C8051F85x/86x family implements 8 kB, 4 kB or 2 kB
of this program memory space as in-system, re-programmable flash memory. The last address in the flash block
(0x1FFF on 8 kB devices, 0x0FFF on 4 kB devices and 0x07FF on 2 kB devices) serves as a security lock byte for
the device, and provides read, write and erase protection. Addresses above the lock byte within the 64 kB address
space are reserved.
C8051F850/3
C8051F860/3
Lock Byte
FLASH memory organized in
512-byte pages
Lock Byte Page
0x1FFF
0x1FFE
0x1E00
C8051F851/4
C8051F861/4
Lock Byte
Lock Byte Page
0x0FFF
0x0FFE
0x0E00
C8051F852/5
C8051F862/5
Lock Byte
Flash Memory Space
Lock Byte Page
Flash Memory Space
0x0000
0x0000
Flash Memory Space
0x07FF
0x07FE
0x0600
0x0000
Figure 8.2. Flash Program Memory Map
8.1.1. MOVX Instruction and Program Memory
The MOVX instruction in an 8051 device is typically used to access external data memory. On the C8051F85x/86x
devices, the MOVX instruction is normally used to read and write on-chip XRAM, but can be re-configured to write
and erase on-chip flash memory space. MOVC instructions are always used to read flash memory, while MOVX
write instructions are used to erase and write flash. This flash access feature provides a mechanism for the
C8051F85x/86x to update program code and use the program memory space for non-volatile data storage. Refer
to Section “10. Flash Memory” on page 54 for further details.
8.2. Data Memory
The C8051F85x/86x device family includes up to 512 bytes of RAM data memory. 256 bytes of this memory is
mapped into the internal RAM space of the 8051. On devices with 512 bytes total RAM, 256 additional bytes of
memory are available as on-chip “external” memory. The data memory map is shown in Figure 8.1 for reference.
8.2.1. Internal RAM
There are 256 bytes of internal RAM mapped into the data memory space from 0x00 through 0xFF. The lower
128 bytes of data memory are used for general purpose registers and scratch pad memory. Either direct or indirect
addressing may be used to access the lower 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, locations 0x20 through 0x2F, may either be addressed as bytes or as 128 bit locations accessible
with the direct addressing mode.
The upper 128 bytes of data memory are accessible only by indirect addressing. This region occupies the same
address space as the Special Function Registers (SFR) but is physically separate from the SFR space. The
addressing mode used by an instruction when accessing locations above 0x7F determines whether the CPU
accesses the upper 128 bytes of data memory space or the SFRs. Instructions that use direct addressing will
access the SFR space. Instructions using indirect addressing above 0x7F access the upper 128 bytes of data
memory. Figure 8.1 illustrates the data memory organization of the C8051F85x/86x.
Preliminary Rev 0.6
47
Memory Organization
C8051F85x/86x
Memory Organization
C8051F85x/86x
8.2.1.1. General Purpose Registers
The lower 32 bytes of data memory, locations 0x00 through 0x1F, may be addressed as four banks of generalpurpose registers. Each bank consists of eight byte-wide registers designated R0 through R7. Only one of these
banks may be enabled at a time. Two bits in the program status word (PSW) register, RS0 and RS1, select the
active register bank. This allows fast context switching when entering subroutines and interrupt service routines.
Indirect addressing modes use registers R0 and R1 as index registers.
8.2.1.2. Bit Addressable Locations
In addition to direct access to data memory organized as bytes, the sixteen data memory locations at 0x20 through
0x2F are also accessible as 128 individually addressable bits. Each bit has a bit address from 0x00 to 0x7F. Bit 0 of
the byte at 0x20 has bit address 0x00 while bit7 of the byte at 0x20 has bit address 0x07. Bit 7 of the byte at 0x2F
has bit address 0x7F. A bit access is distinguished from a full byte access by the type of instruction used (bit source
or destination operands as opposed to a byte source or destination).
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.
8.2.1.3. Stack
A programmer's stack can be located anywhere in the 256-byte data memory. The stack area is designated using
the Stack Pointer (SP) SFR. The SP will point to the last location used. The next value pushed on the stack is
placed at SP+1 and then SP is incremented. A reset initializes the stack pointer to location 0x07. Therefore, the
first value pushed on the stack is placed at location 0x08, which is also the first register (R0) of register bank 1.
Thus, if more than one register bank is to be used, the SP should be initialized to a location in the data memory not
being used for data storage. The stack depth can extend up to 256 bytes.
8.2.2. External RAM
On devices with 512 bytes total RAM, there are 256 bytes of on-chip RAM mapped into the external data memory
space. All of these address locations may be accessed using the external move instruction (MOVX) and the data
pointer (DPTR), or using MOVX indirect addressing mode. Note: the 16-bit MOVX instruction is also used for writes
to the flash memory. See Section “10. Flash Memory” on page 54 for details. The MOVX instruction accesses
XRAM by default.
For a 16-bit MOVX operation (@DPTR), the upper 8 bits of the 16-bit external data memory address word are
"don't cares". As a result, addresses 0x0000 through 0x00FF are mapped modulo style over the entire 64 k
external data memory address range. For example, the XRAM byte at address 0x0000 is shadowed at addresses
0x0100, 0x0200, 0x0300, 0x0400, etc.
8.2.3. 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 CIP-51's resources and peripherals. The CIP-51 duplicates the
SFRs found in a typical 8051 implementation as well as implementing additional SFRs used to configure and
access the sub-systems unique to the MCU. This allows the addition of new functionality while retaining
compatibility with the MCS-51™ instruction set.
The SFR registers are accessed anytime the direct addressing mode is used to access memory locations from
0x80 to 0xFF. SFRs with addresses ending in 0x0 or 0x8 (e.g. P0, TCON, SCON0, IE, etc.) are bit-addressable as
well as byte-addressable. All other SFRs are byte-addressable only. Unoccupied addresses in the SFR space are
reserved for future use. Accessing these areas will have an indeterminate effect and should be avoided.
48
Preliminary Rev 0.6
9. Special Function Register Memory Map
This section details the special function register memory map for the C8051F85x/86x devices.
Table 9.1. Special Function Register (SFR) Memory Map
F8
SPI0CN
PCA0L
PCA0H
F0
B
P0MDIN
P1MDIN
E8 ADC0CN0
PCA0CPL0 PCA0CPH0
EIP1
-
PCA0CPL1 PCA0CPH1 PCA0CPL2 PCA0CPH2
XBR1
XBR2
IT01CF
P0MAT
P0MASK
VDM0CN
-
PRTDRV
PCA0PWM
P1MAT
P1MASK
RSTSRC
-
EIE1
-
E0
ACC
XBR0
D8
PCA0CN
PCA0MD
PCA0CPM0 PCA0CPM1 PCA0CPM2
CRC0IN
CRC0DAT
ADC0PWR
D0
PSW
REF0CN
CRC0AUTO CRC0CNT
P0SKIP
P1SKIP
SMB0ADM
SMB0ADR
C8
TMR2CN
REG0CN
TMR2RLL
TMR2RLH
TMR2L
TMR2H
CRC0CN
CRC0FLIP
C0
SMB0CN
SMB0CF
SMB0DAT
ADC0GTL
ADC0GTH
ADC0LTL
ADC0LTH
OSCICL
B8
IP
ADC0TK
-
ADC0MX
ADC0CF
ADC0L
ADC0H
CPT1CN
B0
-
OSCLCN
ADC0CN1
ADC0AC
-
DEVICEID
REVID
FLKEY
A8
IE
CLKSEL
CPT1MX
CPT1MD
SMB0TC
DERIVID
-
-
A0
P2
SPI0CFG
SPI0CKR
SPI0DAT
P0MDOUT
P1MDOUT
P2MDOUT
-
98
SCON0
SBUF0
-
CPT0CN
PCA0CLR
CPT0MD
PCA0CENT
CPT0MX
90
P1
TMR3CN
TMR3RLL
TMR3RLH
TMR3L
TMR3H
PCA0POL
WDTCN
88
TCON
TMOD
TL0
TL1
TH0
TH1
CKCON
PSCTL
80
P0
SP
DPL
DPH
-
-
-
PCON
0(8)
1(9)
2(A)
3(B)
4(C)
5(D)
6(E)
7(F)
(bit addressable)
Table 9.2. Special Function Registers
Register
Address
Register Description
Page
ACC
0xE0
Accumulator
115
ADC0AC
0xB3
ADC0 Accumulator Configuration
94
ADC0CF
0xBC
ADC0 Configuration
93
ADC0CN0
0xE8
ADC0 Control 0
91
ADC0CN1
0xB2
ADC0 Control 1
92
ADC0GTH
0xC4
ADC0 Greater-Than High Byte
99
ADC0GTL
0xC3
ADC0 Greater-Than Low Byte
100
ADC0H
0xBE
ADC0 Data Word High Byte
97
ADC0L
0xBD
ADC0 Data Word Low Byte
98
Preliminary Rev 0.6
49
Special Function Register Memory Map
C8051F85x/86x
Special Function Register Memory Map
C8051F85x/86x
Table 9.2. Special Function Registers (Continued)
Register
Address
ADC0LTH
0xC6
ADC0 Less-Than High Byte
101
ADC0LTL
0xC5
ADC0 Less-Than Low Byte
102
ADC0MX
0xBB
ADC0 Multiplexer Selection
103
ADC0PWR
0xDF
ADC0 Power Control
95
ADC0TK
0xB9
ADC0 Burst Mode Track Time
96
B
0xF0
B Register
116
CKCON
0x8E
Clock Control
260
CLKSEL
0xA9
Clock Selection
122
CPT0CN
0x9B
Comparator 0 Control
127
CPT0MD
0x9D
Comparator 0 Mode
128
CPT0MX
0x9F
Comparator 0 Multiplexer Selection
129
CPT1CN
0xBF
Comparator 1 Control
130
CPT1MD
0xAB
Comparator 1 Mode
131
CPT1MX
0xAA
Comparator 1 Multiplexer Selection
132
CRC0AUTO
0xD2
CRC0 Automatic Control
139
CRC0CN
0xCE
CRC0 Control
136
CRC0CNT
0xD3
CRC0 Automatic Flash Sector Count
140
CRC0DAT
0xDE
CRC0 Data Output
138
CRC0FLIP
0xCF
CRC0 Bit Flip
141
CRC0IN
0xDD
CRC0 Data Input
137
DERIVID
0xAD
Derivative Identification
63
DEVICEID
0xB5
Device Identification
62
DPH
0x83
Data Pointer Low
113
DPL
0x82
Data Pointer High
112
EIE1
0xE6
Extended Interrupt Enable 1
70
EIP1
0xF3
Extended Interrupt Priority 1
71
FLKEY
0xB7
Flash Lock and Key
60
IE
0xA8
Interrupt Enable
67
IP
0xB8
Interrupt Priority
69
50
Register Description
Preliminary Rev 0.6
Page
Table 9.2. Special Function Registers (Continued)
Register
Address
Register Description
Page
IT01CF
0xE4
INT0 / INT1 Configuration
143
OSCICL
0xC7
High Frequency Oscillator Calibration
120
OSCLCN
0xB1
Low Frequency Oscillator Control
121
P0
0x80
Port 0 Pin Latch
192
P0MASK
0xFE
Port 0 Mask
190
P0MAT
0xFD
Port 0 Match
191
P0MDIN
0xF1
Port 0 Input Mode
193
P0MDOUT
0xA4
Port 0 Output Mode
194
P0SKIP
0xD4
Port 0 Skip
195
P1
0x90
Port 1 Pin Latch
198
P1MASK
0xEE
Port 1 Mask
196
P1MAT
0xED
Port 1 Match
197
P1MDIN
0xF2
Port 1 Input Mode
199
P1MDOUT
0xA5
Port 1 Output Mode
200
P1SKIP
0xD5
Port 1 Skip
201
P2
0xA0
Port 2 Pin Latch
202
P2MDOUT
0xA6
Port 2 Output Mode
203
PCA0CENT
0x9E
PCA Center Alignment Enable
170
PCA0CLR
0x9C
PCA Comparator Clear Control
163
PCA0CN
0xD8
PCA Control
160
PCA0CPH0
0xFC
PCA Capture Module High Byte 0
168
PCA0CPH1
0xEA
PCA Capture Module High Byte 1
174
PCA0CPH2
0xEC
PCA Capture Module High Byte 2
176
PCA0CPL0
0xFB
PCA Capture Module Low Byte 0
167
PCA0CPL1
0xE9
PCA Capture Module Low Byte 1
173
PCA0CPL2
0xEB
PCA Capture Module Low Byte 2
175
PCA0CPM0
0xDA
PCA Capture/Compare Mode 0
164
PCA0CPM1
0xDB
PCA Capture/Compare Mode 1
171
PCA0CPM2
0xDC
PCA Capture/Compare Mode 1
172
Preliminary Rev 0.6
51
Special Function Register Memory Map
C8051F85x/86x
Special Function Register Memory Map
C8051F85x/86x
Table 9.2. Special Function Registers (Continued)
Register
Address
Register Description
Page
PCA0H
0xFA
PCA Counter/Timer Low Byte
166
PCA0L
0xF9
PCA Counter/Timer High Byte
165
PCA0MD
0xD9
PCA Mode
161
PCA0POL
0x96
PCA Output Polarity
169
PCA0PWM
0xF7
PCA PWM Configuration
162
PCON
0x87
Power Control
75
PRTDRV
0xF6
Port Drive Strength
189
PSCTL
0x8F
Program Store Control
59
PSW
0xD0
Program Status Word
117
REF0CN
0xD1
Voltage Reference Control
104
REG0CN
0xC9
Voltage Regulator Control
76
REVID
0xB6
Revision Identification
64
RSTSRC
0xEF
Reset Source
211
SBUF0
0x99
UART0 Serial Port Data Buffer
286
SCON0
0x98
UART0 Serial Port Control
284
SMB0ADM
0xD6
SMBus0 Slave Address Mask
250
SMB0ADR
0xD7
SMBus0 Slave Address
249
SMB0CF
0xC1
SMBus0 Configuration
245
SMB0CN
0xC0
SMBus0 Control
247
SMB0DAT
0xC2
SMBus0 Data
251
SMB0TC
0xAC
SMBus0 Timing and Pin Control
246
SP
0x81
Stack Pointer
114
SPI0CFG
0xA1
SPI0 Configuration
224
SPI0CKR
0xA2
SPI0 Clock Control
226
SPI0CN
0xF8
SPI0 Control
225
SPI0DAT
0xA3
SPI0 Data
227
TCON
0x88
Timer 0/1 Control
262
TH0
0x8C
Timer 0 High Byte
266
TH1
0x8D
Timer 1 High Byte
267
52
Preliminary Rev 0.6
Table 9.2. Special Function Registers (Continued)
Register
Address
Register Description
Page
TL0
0x8A
Timer 0 Low Byte
264
TL1
0x8B
Timer 1 Low Byte
265
TMOD
0x89
Timer 0/1 Mode
263
TMR2CN
0xC8
Timer 2 Control
268
TMR2H
0xCD
Timer 2 High Byte
272
TMR2L
0xCC
Timer 2 Low Byte
271
TMR2RLH
0xCB
Timer 2 Reload High Byte
270
TMR2RLL
0xCA
Timer 2 Reload Low Byte
269
TMR3CN
0x91
Timer 3 Control
273
TMR3H
0x95
Timer 3 High Byte
277
TMR3L
0x94
Timer 3 Low Byte
276
TMR3RLH
0x93
Timer 3 Reload High Byte
275
TMR3RLL
0x92
Timer 3 Reload Low Byte
274
VDM0CN
0xFF
Supply Monitor Control
212
WDTCN
0x97
Watchdog Timer Control
290
XBR0
0xE1
Port I/O Crossbar 0
186
XBR1
0xE2
Port I/O Crossbar 1
187
XBR2
0xE3
Port I/O Crossbar 2
188
Preliminary Rev 0.6
53
Special Function Register Memory Map
C8051F85x/86x
Flash Memory
C8051F85x/86x
10. Flash Memory
On-chip, re-programmable flash memory is included for program code and non-volatile data storage. The flash
memory is organized in 512-byte pages. It can be erased and written through the C2 interface or from firmware by
overloading the MOVX instruction. Any individual byte in flash memory must only be written once between page
erase operations.
10.1. Security Options
The CIP-51 provides security options to protect the flash memory from inadvertent modification by software as well
as to prevent the viewing of proprietary program code and constants. The Program Store Write Enable (bit PSWE
in register PSCTL) and the Program Store Erase Enable (bit PSEE in register PSCTL) bits protect the flash
memory from accidental modification by software. PSWE must be explicitly set to ‘1’ before software can modify
the flash memory; both PSWE and PSEE must be set to ‘1’ before software can erase flash memory. Additional
security features prevent proprietary program code and data constants from being read or altered across the C2
interface.
A Security Lock Byte located in flash user space offers protection of the flash program memory from access (reads,
writes, or erases) by unprotected code or the C2 interface. See Section “8. Memory Organization” on page 46 for
the location of the security byte. The flash security mechanism allows the user to lock n 512-byte flash pages,
starting at page 0 (addresses 0x0000 to 0x01FF), where n is the 1’s complement number represented by the
Security Lock Byte. Note that the page containing the flash Security Lock Byte is unlocked when no other
flash pages are locked (all bits of the Lock Byte are ‘1’) and locked when any other flash pages are locked
(any bit of the Lock Byte is ‘0’). An example is shown in Figure 10.1.
Security Lock Byte:
11111101b
1s Complement:
00000010b
Flash pages locked:
3 (First two flash pages + Lock Byte Page)
Figure 10.1. Security Byte Decoding
The level of flash security depends on the flash access method. The three flash access methods that can be
restricted are reads, writes, and erases from the C2 debug interface, user firmware executing on unlocked pages,
and user firmware executing on locked pages. Table 10.1 summarizes the flash security features of the
C8051F85x/86x devices.
Table 10.1. Flash Security Summary
Action
C2 Debug
Interface
User Firmware executing from:
an unlocked page
a locked page
Permitted
Permitted
Permitted
Not Permitted
Flash Error Reset
Permitted
Read or Write page containing Lock Byte
(if no pages are locked)
Permitted
Permitted
N/A
Read or Write page containing Lock Byte
(if any page is locked)
Not Permitted
Flash Error Reset
Permitted
Permitted
Permitted
N/A
Read, Write or Erase unlocked pages
(except page with Lock Byte)
Read, Write or Erase locked pages
(except page with Lock Byte)
Read contents of Lock Byte
(if no pages are locked)
54
Preliminary Rev 0.6
Table 10.1. Flash Security Summary
Read contents of Lock Byte
(if any page is locked)
Not Permitted
Flash Error Reset
Permitted
Permitted
Permitted
N/A
C2 Device Erase
Only
Flash Error Reset
Flash Error Reset
Lock additional pages
(change 1s to 0s in the Lock Byte)
Not Permitted
Flash Error Reset
Flash Error Reset
Unlock individual pages
(change 0s to 1s in the Lock Byte)
Not Permitted
Flash Error Reset
Flash Error Reset
Read, Write or Erase Reserved Area
Not Permitted
Flash Error Reset
Flash Error Reset
Erase page containing Lock Byte
(if no pages are locked)
Erase page containing Lock Byte—Unlock all
pages (if any page is locked)

C2 Device Erase—Erases all flash pages including the page containing the Lock Byte.
Flash Error Reset —Not permitted; Causes Flash Error Device Reset (FERROR bit in RSTSRC is '1' after reset).
- All prohibited operations that are performed via the C2 interface are ignored (do not cause device reset).
- Locking any flash page also locks the page containing the Lock Byte.
- Once written to, the Lock Byte cannot be modified except by performing a C2 Device Erase.
- If user code writes to the Lock Byte, the Lock does not take effect until the next device reset.
Preliminary Rev 0.6
55
Flash Memory
C8051F85x/86x
Flash Memory
C8051F85x/86x
10.2. Programming The Flash Memory
Writes to flash memory clear bits from logic 1 to logic 0, and can be performed on single byte locations. Flash
erasures set bits back to logic 1, and occur only on full pages. The write and erase operations are automatically
timed by hardware for proper execution; data polling to determine the end of the write/erase operation is not
required. Code execution is stalled during a flash write/erase operation.
The simplest means of programming the flash memory is through the C2 interface using programming tools
provided by Silicon Labs or a third party vendor. This is the only means for programming a non-initialized device.
To ensure the integrity of flash contents, it is strongly recommended that the on-chip supply monitor be enabled in
any system that includes code that writes and/or erases flash memory from software.
10.2.1. Flash Lock and Key Functions
Flash writes and erases by user software are protected with a lock and key function. The Flash Lock and Key
Register (FLKEY) must be written with the correct key codes, in sequence, before flash operations may be
performed. The key codes are: 0xA5, 0xF1. The timing does not matter, but the codes must be written in order. If
the key codes are written out of order, or the wrong codes are written, flash writes and erases will be disabled until
the next system reset. Flash writes and erases will also be disabled if a flash write or erase is attempted before the
key codes have been written properly. The flash lock resets after each write or erase; the key codes must be
written again before a following flash operation can be performed.
10.2.2. Flash Erase Procedure
The flash memory can be programmed by software using the MOVX write instruction with the address and data
byte to be programmed provided as normal operands. Before writing to flash memory using MOVX, flash write
operations must be enabled by: (1) setting the PSWE Program Store Write Enable bit in the PSCTL register to
logic 1 (this directs the MOVX writes to target flash memory); and (2) Writing the flash key codes in sequence to the
Flash Lock register (FLKEY). The PSWE bit remains set until cleared by software.
A write to flash memory can clear bits to logic 0 but cannot set them; only an erase operation can set bits to logic 1
in flash. A byte location to be programmed should be erased before a new value is written. Erase operation
applies to an entire page (setting all bytes in the page to 0xFF). To erase an entire page, perform the following
steps:
1. Disable interrupts (recommended).
2. Set the PSEE bit (register PSCTL).
3. Set the PSWE bit (register PSCTL).
4. Write the first key code to FLKEY: 0xA5.
5. Write the second key code to FLKEY: 0xF1.
6. Using the MOVX instruction, write a data byte to any location within the page to be erased.
7. Clear the PSWE and PSEE bits.
10.2.3. Flash Write Procedure
Flash bytes are programmed by software with the following sequence:
1. Disable interrupts (recommended).
2. Erase the flash page containing the target location, as described in Section 10.2.2.
3. Set the PSWE bit (register PSCTL).
4. Clear the PSEE bit (register PSCTL).
5. Write the first key code to FLKEY: 0xA5.
6. Write the second key code to FLKEY: 0xF1.
7. Using the MOVX instruction, write a single data byte to the desired location within the desired page.
8. Clear the PSWE bit.
Steps 5–7 must be repeated for each byte to be written. After flash writes are complete, PSWE should be cleared
so that MOVX instructions do not target program memory.
56
Preliminary Rev 0.6
10.3. Non-volatile Data Storage
The flash memory can be used for non-volatile data storage as well as program code. This allows data such as
calibration coefficients to be calculated and stored at run time. Data is written using the MOVX write instruction and
read using the MOVC instruction. Note: MOVX read instructions always target XRAM.
10.4. Flash Write and Erase Guidelines
Any system which contains routines which write or erase flash memory from software involves some risk that the
write or erase routines will execute unintentionally if the CPU is operating outside its specified operating range of
supply voltage, system clock frequency or temperature. This accidental execution of flash modifying code can
result in alteration of flash memory contents causing a system failure that is only recoverable by re-flashing the
code in the device.
To help prevent the accidental modification of flash by firmware, hardware restricts flash writes and erasures when
the supply monitor is not active and selected as a reset source. As the monitor is enabled and selected as a reset
source by default, it is recommended that systems writing or erasing flash simply maintain the default state.
The following guidelines are recommended for any system which contains routines which write or erase flash from
code.
10.4.1. Voltage Supply Maintenance and the Supply Monitor
1. If the system power supply is subject to voltage or current "spikes," add sufficient transient protection
devices to the power supply to ensure that the supply voltages listed in the Absolute Maximum Ratings
table are not exceeded.
2. Make certain that the minimum supply rise time specification is met. If the system cannot meet this rise
time specification, then add an external supply brownout circuit to the RST pin of the device that holds the
device in reset until the voltage supply reaches the lower limit, and re-asserts RST if the supply drops
below the low supply limit.
3. Do not disable the supply monitor. If the supply monitor must be disabled in the system, firmware should be
added to the startup routine to enable the on-chip supply monitor and enable the supply monitor as a reset
source as early in code as possible. This should be the first set of instructions executed after the reset
vector. For C-based systems, this may involve modifying the startup code added by the C compiler. See
your compiler documentation for more details. Make certain that there are no delays in software between
enabling the supply monitor and enabling the supply monitor as a reset source. Code examples showing
this can be found in “AN201: Writing to Flash From Firmware", available from the Silicon Laboratories web
site. Note that the supply monitor must be enabled and enabled as a reset source when writing or
erasing flash memory. A flash error reset will occur if either condition is not met.
4. As an added precaution if the supply monitor is ever disabled, explicitly enable the supply monitor and
enable the supply monitor as a reset source inside the functions that write and erase flash memory. The
supply monitor enable instructions should be placed just after the instruction to set PSWE to a 1, but before
the flash write or erase operation instruction.
5. Make certain that all writes to the RSTSRC (Reset Sources) register use direct assignment operators and
explicitly DO NOT use the bit-wise operators (such as AND or OR). For example, "RSTSRC = 0x02" is
correct. "RSTSRC |= 0x02" is incorrect.
6. Make certain that all writes to the RSTSRC register explicitly set the PORSF bit to a '1'. Areas to check are
initialization code which enables other reset sources, such as the Missing Clock Detector or Comparator,
for example, and instructions which force a Software Reset. A global search on "RSTSRC" can quickly
verify this.
10.4.2. PSWE Maintenance
7. Reduce the number of places in code where the PSWE bit (in register PSCTL) is set to a 1. There should
be exactly one routine in code that sets PSWE to a '1' to write flash bytes and one routine in code that sets
PSWE and PSEE both to a '1' to erase flash pages.
8. Minimize the number of variable accesses while PSWE is set to a 1. Handle pointer address updates and
loop variable maintenance outside the "PSWE = 1;... PSWE = 0;" area. Code examples showing this can
Preliminary Rev 0.6
57
Flash Memory
C8051F85x/86x
Flash Memory
C8051F85x/86x
be found in “AN201: Writing to Flash From Firmware", available from the Silicon Laboratories web site.
9. Disable interrupts prior to setting PSWE to a '1' and leave them disabled until after PSWE has been reset
to 0. Any interrupts posted during the flash write or erase operation will be serviced in priority order after
the flash operation has been completed and interrupts have been re-enabled by software.
10. Make certain that the flash write and erase pointer variables are not located in XRAM. See your compiler
documentation for instructions regarding how to explicitly locate variables in different memory areas.
11. Add address bounds checking to the routines that write or erase flash memory to ensure that a routine
called with an illegal address does not result in modification of the flash.
10.4.3. System Clock
12. If operating from an external crystal-based source, be advised that crystal performance is susceptible to
electrical interference and is sensitive to layout and to changes in temperature. If the system is operating in
an electrically noisy environment, use the internal oscillator or use an external CMOS clock.
13. If operating from the external oscillator, switch to the internal oscillator during flash write or erase
operations. The external oscillator can continue to run, and the CPU can switch back to the external
oscillator after the flash operation has completed.
Additional flash recommendations and example code can be found in “AN201: Writing to Flash From Firmware",
available from the Silicon Laboratories website.
58
Preliminary Rev 0.6
10.5. Flash Control Registers
Register 10.1. PSCTL: Program Store Control
Bit
7
6
5
4
3
2
1
0
Name
Reserved
PSEE
PSWE
Type
R
RW
RW
0
0
Reset
0
0
0
0
0
0
SFR Address: 0x8F
Table 10.2. PSCTL Register Bit Descriptions
Bit
Name
7:2
Reserved
1
PSEE
Function
Must write reset value.
Program Store Erase Enable.
Setting this bit (in combination with PSWE) allows an entire page of flash program memory to be erased. If this bit is logic 1 and flash writes are enabled (PSWE is logic 1), a
write to flash memory using the MOVX instruction will erase the entire page that contains
the location addressed by the MOVX instruction. The value of the data byte written does
not matter.
0: Flash program memory erasure disabled.
1: Flash program memory erasure enabled.
0
PSWE
Program Store Write Enable.
Setting this bit allows writing a byte of data to the flash program memory using the MOVX
write instruction. The flash location should be erased before writing data.
0: Writes to flash program memory disabled.
1: Writes to flash program memory enabled; the MOVX write instruction targets flash
memory.
Preliminary Rev 0.6
59
Flash Memory
C8051F85x/86x
Flash Memory
C8051F85x/86x
Register 10.2. FLKEY: Flash Lock and Key
Bit
7
6
5
4
Name
FLKEY
Type
RW
Reset
0
0
0
0
3
2
1
0
0
0
0
0
SFR Address: 0xB7
Table 10.3. FLKEY Register Bit Descriptions
Bit
Name
7:0
FLKEY
Function
Flash Lock and Key Register.
Write:
This register provides a lock and key function for flash erasures and writes. Flash writes
and erases are enabled by writing 0xA5 followed by 0xF1 to the FLKEY register. Flash
writes and erases are automatically disabled after the next write or erase is complete. If
any writes to FLKEY are performed incorrectly, or if a flash write or erase operation is
attempted while these operations are disabled, the flash will be permanently locked from
writes or erasures until the next device reset. If an application never writes to flash, it can
intentionally lock the flash by writing a non-0xA5 value to FLKEY from software.
Read:
When read, bits 1-0 indicate the current flash lock state.
00: Flash is write/erase locked.
01: The first key code has been written (0xA5).
10: Flash is unlocked (writes/erases allowed).
11: Flash writes/erases are disabled until the next reset.
60
Preliminary Rev 0.6
Device Identification
C8051F85x/86x
11. Device Identification
The C8051F85x/86x has SFRs that identify the device family, derivative, and revision. These SFRs can be read by
firmware at runtime to determine the capabilities of the MCU that is executing code. This allows the same firmware
image to run on MCUs with different memory sizes and peripherals, and dynamically change functionality to suit
the capabilities of that MCU.
11.1. Device Identification Registers
Register 11.1. DEVICEID: Device Identification
Bit
7
6
5
4
Name
DEVICEID
Type
R
Reset
0
0
1
1
3
2
1
0
0
0
0
0
SFR Address: 0xB5
Table 11.1. DEVICEID Register Bit Descriptions
Bit
Name
7:0
DEVICEID
Function
Device ID.
This read-only register returns the 8-bit device ID: 0x30 (C8051F85x/86x).
62
Preliminary Rev 0.6
Register 11.2. DERIVID: Derivative Identification
Bit
7
6
5
4
Name
DERIVID
Type
R
Reset
X
X
X
X
3
2
1
0
X
X
X
X
SFR Address: 0xAD
Table 11.2. DERIVID Register Bit Descriptions
Bit
Name
7:0
DERIVID
Function
Derivative ID.
This read-only register returns the 8-bit derivative ID, which can be used by firmware to
identify which device in the product family the code is executing on.
0xD0: C8051F850-GU
0xD1: C8051F851-GU
0xD2: C8051F852-GU
0xD3: C8051F853-GU
0xD4: C8051F854-GU
0xD5: C8051F855-GU
0xE0: C8051F860-GS
0xE1: C8051F861-GS
0xE2: C8051F862-GS
0xE3: C8051F863-GS
0xE4: C8051F864-GS
0xE5: C8051F865-GS
0xF0: C8051F850-GM
0xF1: C8051F851-GM
0xF2: C8051F852-GM
0xF3: C8051F853-GM
0xF4: C8051F854-GM
0xF5: C8051F855-GM
Preliminary Rev 0.6
63
Device Identification
C8051F85x/86x
Device Identification
C8051F85x/86x
Register 11.3. REVID: Revision Identifcation
Bit
7
6
5
4
Name
REVID
Type
R
Reset
X
X
X
X
3
2
1
0
X
X
X
X
SFR Address: 0xB6
Table 11.3. REVID Register Bit Descriptions
Bit
Name
7:0
REVID
Function
Revision ID.
This read-only register returns the 8-bit revision ID.
00000000: Revision A
00000001: Revision B
00000010: Revision C
00000011-11111111: Reserved.
64
Preliminary Rev 0.6
12. Interrupts
The C8051F85x/86x includes an extended interrupt system supporting multiple interrupt sources with two priority
levels. The allocation of interrupt sources between on-chip peripherals and external input pins varies according to
the specific version of the device. Each interrupt source has one or more associated interrupt-pending flag(s)
located in an SFR. When a peripheral or external source meets a valid interrupt condition, the associated interruptpending flag is set to logic 1.
If interrupts are enabled for the source, an interrupt request is generated when the interrupt-pending flag is set. As
soon as execution of the current instruction is complete, the CPU generates an LCALL to a predetermined address
to begin execution of an interrupt service routine (ISR). Each ISR must end with an RETI instruction, which returns
program execution to the next instruction that would have been executed if the interrupt request had not occurred.
If interrupts are not enabled, the interrupt-pending flag is ignored by the hardware and program execution
continues as normal. The interrupt-pending flag is set to logic 1 regardless 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 and EIE1). However, interrupts must first be globally enabled by setting the EA bit in the IE register to
logic 1 before the individual interrupt enables are recognized. Setting the EA bit to logic 0 disables all interrupt
sources regardless of the individual interrupt-enable settings.
Some interrupt-pending flags are automatically cleared by the hardware when the CPU vectors to the ISR.
However, most are not cleared by the hardware and must be cleared by software before returning from the ISR. If
an interrupt-pending flag remains set after the CPU completes the return-from-interrupt (RETI) instruction, a new
interrupt request will be generated immediately and the CPU will re-enter the ISR after the completion of the next
instruction.
12.1. MCU Interrupt Sources and Vectors
The C8051F85x/86x MCUs support interrupt sources for each peripheral on the device. Software can simulate an
interrupt by setting any 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 12.1. 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).
12.1.1. Interrupt Priorities
Each interrupt source can be individually programmed to one of two priority levels: low or high. A low priority
interrupt service routine can be preempted 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 default. If two interrupts are recognized simultaneously, 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 12.1.
12.1.2. Interrupt Latency
Interrupt response time depends on the state of the CPU when the interrupt occurs. Pending interrupts are
sampled and priority decoded each system clock cycle. Therefore, the fastest possible response time is 5 system
clock cycles: 1 clock cycle 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 service
the pending interrupt. Therefore, the maximum response time for an interrupt (when no other interrupt is currently
being serviced or the new interrupt is of greater priority) occurs when the CPU is performing an RETI instruction
followed by a DIV as the next instruction. In this case, the response time is 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.
If more than one interrupt is pending when the CPU exits an ISR, the CPU will service the next highest priority
interrupt that is pending.
Preliminary Rev 0.6
65
Interrupts
C8051F85x/86x
Interrupt Source
Interrupt
Vector
Priority Pending Flags
Order
Cleared by HW?
Table 12.1. Interrupt Summary
Bit addressable?
Interrupts
C8051F85x/86x
Enable Flag
Reset
0x0000
Top
None
N/A
N/A
Always Enabled
External Interrupt 0 (INT0)
0x0003
0
IE0 (TCON.1)
Y
Y
EX0 (IE.0)
Timer 0 Overflow
0x000B
1
TF0 (TCON.5)
Y
Y
ET0 (IE.1)
External Interrupt 1 (INT1)
0x0013
2
IE1 (TCON.3)
Y
Y
EX1 (IE.2)
Timer 1 Overflow
0x001B
3
TF1 (TCON.7)
Y
Y
ET1 (IE.3)
UART0
0x0023
4
RI (SCON0.0)
TI (SCON0.1)
Y
N
ES0 (IE.4)
Timer 2 Overflow
0x002B
5
TF2H (TMR2CN.7)
TF2L (TMR2CN.6)
Y
N
ET2 (IE.5)
SPI0
0x0033
6
SPIF (SPI0CN.7)
WCOL (SPI0CN.6)
MODF (SPI0CN.5)
RXOVRN (SPI0CN.4)
Y
N
ESPI0 (IE.6)
SMB0
0x003B
7
SI (SMB0CN.0)
Y
N
ESMB0 (EIE1.0)
Port Match
0x0043
8
None
N/A
N/A
EMAT (EIE1.1)
ADC0 Window Compare
0x004B
9
ADWINT (ADC0CN.3)
Y
N
EWADC0 (EIE1.2)
ADC0 Conversion Complete
0x0053
10
ADINT (ADC0CN.5)
Y
N
EADC0 (EIE1.3)
Programmable Counter
Array
0x005B
11
CF (PCA0CN.7)
CCFn (PCA0CN.n)
COVF (PCA0PWM.6)
Y
N
EPCA0 (EIE1.4)
Comparator0
0x0063
12
CPFIF (CPT0CN.4)
CPRIF (CPT0CN.5)
N
N
ECP0 (EIE1.5)
Comparator1
0x006B
13
CPFIF (CPT1CN.4)
CPRIF (CPT1CN.5)
N
N
ECP1 (EIE1.6)
Timer 3 Overflow
0x0073
14
TF3H (TMR3CN.7)
TF3L (TMR3CN.6)
N
N
ET3 (EIE1.7)
66
Preliminary Rev 0.6
12.2. Interrupt Control Registers
Register 12.1. IE: Interrupt Enable
Bit
7
6
5
4
3
2
1
0
Name
EA
ESPI0
ET2
ES0
ET1
EX1
ET0
EX0
Type
RW
RW
RW
RW
RW
RW
RW
RW
Reset
0
0
0
0
0
0
0
0
SFR Address: 0xA8 (bit-addressable)
Table 12.2. IE Register Bit Descriptions
Bit
Name
7
EA
Function
Enable All Interrupts.
Globally enables/disables all interrupts and overrides individual interrupt mask settings.
0: Disable all interrupt sources.
1: Enable each interrupt according to its individual mask setting.
6
ESPI0
Enable SPI0 Interrupt.
This bit sets the masking of the SPI0 interrupts.
0: Disable all SPI0 interrupts.
1: Enable interrupt requests generated by SPI0.
5
ET2
Enable Timer 2 Interrupt.
This bit sets 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.
3
ET1
Enable Timer 1 Interrupt.
This bit sets 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.
1
ET0
Enable Timer 0 Interrupt.
This bit sets the masking of the Timer 0 interrupt.
0: Disable all Timer 0 interrupt.
1: Enable interrupt requests generated by the TF0 flag.
Preliminary Rev 0.6
67
Interrupts
C8051F85x/86x
Interrupts
C8051F85x/86x
Table 12.2. IE Register Bit Descriptions
Bit
Name
0
EX0
Function
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.
68
Preliminary Rev 0.6
Register 12.2. IP: Interrupt Priority
Bit
7
6
5
4
3
2
1
0
Name
Reserved
PSPI0
PT2
PS0
PT1
PX1
PT0
PX0
Type
R
RW
RW
RW
RW
RW
RW
RW
Reset
1
0
0
0
0
0
0
0
SFR Address: 0xB8 (bit-addressable)
Table 12.3. IP Register Bit Descriptions
Bit
Name
7
Reserved
6
PSPI0
Function
Must write reset value.
Serial Peripheral Interface (SPI0) Interrupt Priority Control.
This bit sets the priority of the SPI0 interrupt.
0: SPI0 interrupt set to low priority level.
1: SPI0 interrupt set to high priority level.
5
PT2
Timer 2 Interrupt Priority Control.
This bit sets the priority of the 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 set to high priority level.
3
PT1
Timer 1 Interrupt Priority Control.
This bit sets the priority of the 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.
1
PT0
Timer 0 Interrupt Priority Control.
This bit sets the priority of the 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.
Preliminary Rev 0.6
69
Interrupts
C8051F85x/86x
Interrupts
C8051F85x/86x
Register 12.3. EIE1: Extended Interrupt Enable 1
Bit
7
6
5
4
3
2
1
0
Name
ET3
ECP1
ECP0
EPCA0
EADC0
EWADC0
EMAT
ESMB0
Type
RW
RW
RW
RW
RW
RW
RW
RW
Reset
0
0
0
0
0
0
0
0
SFR Address: 0xE6
Table 12.4. EIE1 Register Bit Descriptions
Bit
Name
7
ET3
Function
Enable Timer 3 Interrupt.
This bit sets the masking of the Timer 3 interrupt.
0: Disable Timer 3 interrupts.
1: Enable interrupt requests generated by the TF3L or TF3H flags.
6
ECP1
Enable Comparator1 (CP1) Interrupt.
This bit sets the masking of the CP1 interrupt.
0: Disable CP1 interrupts.
1: Enable interrupt requests generated by the comparator 1 CPRIF or CPFIF flags.
5
ECP0
Enable Comparator0 (CP0) Interrupt.
This bit sets the masking of the CP0 interrupt.
0: Disable CP0 interrupts.
1: Enable interrupt requests generated by the comparator 0 CPRIF or CPFIF flags.
4
EPCA0
Enable Programmable Counter Array (PCA0) Interrupt.
This bit sets the masking of the PCA0 interrupts.
0: Disable all PCA0 interrupts.
1: Enable interrupt requests generated by PCA0.
3
EADC0
Enable ADC0 Conversion Complete Interrupt.
This bit sets the masking of the ADC0 Conversion Complete interrupt.
0: Disable ADC0 Conversion Complete interrupt.
1: Enable interrupt requests generated by the ADINT flag.
2
EWADC0
Enable Window Comparison ADC0 Interrupt.
This bit sets the masking of ADC0 Window Comparison interrupt.
0: Disable ADC0 Window Comparison interrupt.
1: Enable interrupt requests generated by ADC0 Window Compare flag (ADWINT).
1
EMAT
Enable Port Match Interrupts.
This bit sets the masking of the Port Match Event interrupt.
0: Disable all Port Match interrupts.
1: Enable interrupt requests generated by a Port Match.
0
ESMB0
Enable SMBus (SMB0) Interrupt.
This bit sets the masking of the SMB0 interrupt.
0: Disable all SMB0 interrupts.
1: Enable interrupt requests generated by SMB0.
70
Preliminary Rev 0.6
Register 12.4. EIP1: Extended Interrupt Priority 1
Bit
7
6
5
4
3
2
1
0
Name
PT3
PCP1
PCP0
PPCA0
PADC0
PWADC0
PMAT
PSMB0
Type
RW
RW
RW
RW
RW
RW
RW
RW
Reset
0
0
0
0
0
0
0
0
SFR Address: 0xF3
Table 12.5. EIP1 Register Bit Descriptions
Bit
Name
7
PT3
Function
Timer 3 Interrupt Priority Control.
This bit sets the priority of the Timer 3 interrupt.
0: Timer 3 interrupts set to low priority level.
1: Timer 3 interrupts set to high priority level.
6
PCP1
Comparator1 (CP1) Interrupt Priority Control.
This bit sets the priority of the CP1 interrupt.
0: CP1 interrupt set to low priority level.
1: CP1 interrupt set to high priority level.
5
PCP0
Comparator0 (CP0) Interrupt Priority Control.
This bit sets the priority of the CP0 interrupt.
0: CP0 interrupt set to low priority level.
1: CP0 interrupt set to high priority level.
4
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.
3
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.
2
PWADC0
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.
1
PMAT
Port Match Interrupt Priority Control.
This bit sets the priority of the Port Match Event interrupt.
0: Port Match interrupt set to low priority level.
1: Port Match interrupt set to high priority level.
Preliminary Rev 0.6
71
Interrupts
C8051F85x/86x
Interrupts
C8051F85x/86x
Table 12.5. EIP1 Register Bit Descriptions
Bit
Name
0
PSMB0
Function
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.
72
Preliminary Rev 0.6
Power Management and Internal Regulator
C8051F85x/86x
13. Power Management and Internal Regulator
All internal circuitry on the C8051F85x/86x devices draws power from the VDD supply pin. Circuits with external
connections (I/O pins, analog muxes) are powered directly from the VDD supply voltage, while most of the internal
circuitry is supplied by an on-chip LDO regulator. The regulator output is fully internal to the device, and is available
also as an ADC input or reference source for the comparators and ADC.
The devices support the standard 8051 power modes: idle and stop. For further power savings in stop mode, the
internal LDO regulator may be disabled, shutting down the majority of the power nets on the device.
Although the C8051F85x/86x 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 and serial buses, have their clocks gated
off and draw little power when they are not in use.
13.1. Power Modes
Idle mode halts the CPU while leaving the peripherals and clocks active. In stop mode, the CPU is halted, all
interrupts and timers are inactive, and the internal oscillator 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 majority of the device is shut down with no clocks active. The
Power Control Register (PCON) is used to control the C8051F85x/86x's Stop and Idle power management modes.
13.1.1. Idle Mode
Setting the Idle Mode Select bit (PCON.0) causes the hardware to halt the CPU and enter idle mode as soon as
the instruction that sets the bit completes execution. All internal registers and memory maintain their original data.
All analog and digital peripherals can remain active during idle mode.
Idle mode is terminated when an enabled interrupt is asserted or a reset occurs. The assertion of an enabled
interrupt will cause the Idle Mode Selection bit (PCON.0) to be cleared and the CPU to resume operation. The
pending interrupt will be serviced and the next instruction to be executed after the return from interrupt (RETI) will
be the instruction immediately following the one that set the Idle Mode Select bit. If idle mode is terminated by an
internal or external reset, the CIP-51 performs a normal reset sequence and begins program execution at address
0x0000.
Note: If the instruction following the write of the IDLE bit is a single-byte instruction and an interrupt occurs during the
execution phase of the instruction that sets the IDLE bit, the CPU may not wake from Idle mode when a future interrupt
occurs. Therefore, instructions that set the IDLE bit should be followed by an instruction that has two or more opcode
bytes, for example:
// in ‘C’:
// set IDLE bit
PCON |= 0x01;
PCON = PCON;
// ... followed by a 3-cycle dummy instruction
; in assembly:
ORL PCON, #01h
MOV PCON, PCON
; set IDLE bit
; ... followed by a 3-cycle dummy instruction
If enabled, the Watchdog Timer (WDT) will eventually cause an internal watchdog reset and thereby terminate 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 provides the opportunity for additional
power savings, allowing the system to remain in the Idle mode indefinitely, waiting for an external stimulus to wake
up the system.
74
Preliminary Rev 0.6
13.1.2. Stop Mode
Setting the Stop Mode Select bit (PCON.1) causes the controller core to enter Stop mode as soon as the
instruction that sets the bit completes execution. Before entering stop mode, the system clock must be sourced by
the internal high-frequency oscillator. In stop mode the internal oscillator, CPU, and all digital peripherals are
stopped; the state of the external oscillator circuit is not affected. Each analog peripheral (including the external
oscillator circuit) may be shut down individually prior to entering stop mode. Stop mode can only be terminated by
an internal or external reset. On reset, the device performs the normal reset sequence and begins program
execution at address 0x0000.
If enabled, the Missing Clock Detector will cause an internal reset and thereby terminate the stop mode. The
Missing Clock Detector should be disabled if the CPU is to be put to in STOP mode for longer than the MCD
timeout.
13.2. LDO Regulator
C8051F85x/86x devices include an internal regulator that regulates the internal core and logic supply. Under
default conditions, the internal regulator will remain on when the device enters STOP mode. This allows any
enabled reset source to generate a reset for the device and bring the device out of STOP mode. For additional
power savings, the STOPCF bit can be used to shut down the regulator and the internal power network of the
device when the part enters STOP mode. When STOPCF is set to 1, the RST pin and a full power cycle of the
device are the only methods of generating a reset.
13.3. Power Control Registers
Register 13.1. PCON: Power Control
Bit
7
6
5
4
3
2
1
0
Name
GF
STOP
IDLE
Type
RW
RW
RW
0
0
Reset
0
0
0
0
0
0
SFR Address: 0x87
Table 13.1. PCON Register Bit Descriptions
Bit
Name
7:2
GF
Function
General Purpose Flags 5-0.
These are general purpose flags for use under software control.
1
STOP
Stop Mode Select.
Setting this bit will place the CIP-51 in Stop mode. This bit will always be read as 0.
0
IDLE
Idle Mode Select.
Setting this bit will place the CIP-51 in Idle mode. This bit will always be read as 0.
Preliminary Rev 0.6
75
Power Management and Internal Regulator
C8051F85x/86x
Power Management and Internal Regulator
C8051F85x/86x
13.4. LDO Control Registers
Register 13.2. REG0CN: Voltage Regulator Control
Bit
7
6
5
4
3
2
1
Name
Reserved
STOPCF
Reserved
Type
R
RW
R
Reset
0
0
0
0
0
0
0
0
0
SFR Address: 0xC9
Table 13.2. REG0CN Register Bit Descriptions
Bit
Name
Function
7:4
Reserved
Must write reset value.
3
STOPCF
Stop Mode Configuration.
This bit configures the regulator's behavior when the device enters stop mode.
0: Regulator is still active in stop mode. Any enabled reset source will reset the device.
1: Regulator is shut down in stop mode. Only the RST pin or power cycle can reset the
device.
2:0
76
Reserved
Must write reset value.
Preliminary Rev 0.6
Analog-to-Digital Converter (ADC0)
C8051F85x/86x
14. Analog-to-Digital Converter (ADC0)
The ADC is a successive-approximation-register (SAR) ADC with 12, 10, and 8-bit modes, integrated track-andhold and a programmable window detector. These different modes allow the user to trade off speed for resolution.
ADC0 also has an autonomous low power burst mode which can automatically enable ADC0, capture and
accumulate samples, then place ADC0 in a low power shutdown mode without CPU intervention. It also has a 16bit accumulator that can automatically oversample and average the ADC results.
The ADC is fully configurable under software control via several registers. The ADC0 operates in single-ended
mode and may be configured to measure different signals using the analog multiplexer. The voltage reference for
the ADC is selectable between internal and external reference sources.
ADC0
Input
Selection
Control /
Configuration
P0 Pins (8)
Less
Than
Greater
Than
Window Compare
P1 Pins (8)
0.5x – 1x
gain
VDD
SAR Analog to
Digital Converter
ADWINT
(Window Interrupt)
ADC0
Accumulator
GND
ADINT
(Interrupt Flag)
Internal LDO
Temp
Sensor
ADBUSY (On Demand)
Timer 0 Overflow
1.65 V /
2.4 V
Reference
Internal LDO
VDD
VREF
Timer 2 Overflow
Timer 3 Overflow
CNVSTR (External Pin)
Trigger
Selection
Reference
Selection
Device Ground
AGND
SYSCLK
Clock
Divider
SAR clock
Figure 14.1. ADC0 Functional Block Diagram
78
Preliminary Rev 0.6
14.1. ADC0 Analog Multiplexer
ADC0 on C8051F85x/86x has an analog multiplexer capable of selecting any pin on ports P0 and P1 (up to 16
total), the on-chip temperature sensor, the internal regulated supply, the VDD supply, or GND. ADC0 input
channels are selected using the ADC0MX register.
Table 14.1. ADC0 Input Multiplexer Channels
ADC0MX setting
Signal Name
QSOP24 Pin Name
QFN20 Pin Name
SOIC16 Pin Name
00000
ADC0.0
P0.0
P0.0
P0.0
00001
ADC0.1
P0.1
P0.1
P0.1
00010
ADC0.2
P0.2
P0.2
P0.2
00011
ADC0.3
P0.3
P0.3
P0.3
00100
ADC0.4
P0.4
P0.4
P0.4
00101
ADC0.5
P0.5
P0.5
P0.5
00110
ADC0.6
P0.6
P0.6
P0.6
00111
ADC0.7
P0.7
P0.7
P0.7
01000
ADC0.8
P1.0
P1.0
P1.0
01001
ADC0.9
P1.1
P1.1
P1.1
01010
ADC0.10
P1.2
P1.2
P1.2
01011
ADC0.11
P1.3
P1.3
P1.3
01100
ADC0.12
P1.4
P1.4
Reserved
01101
ADC0.13
P1.5
P1.5
Reserved
01110
ADC0.14
P1.6
P1.6
Reserved
01111
ADC0.15
P1.7
Reserved
Reserved
10000
Temp Sensor
Internal Temperature Sensor
10001
LDO
Internal 1.8 V LDO Output
10010
VDD
VDD Supply Pin
10011
GND
GND Supply Pin
10100-11111
None
No connection
Important note about ADC0 input configuration: Port pins selected as ADC0 inputs should be configured as analog
inputs, and should be skipped by the crossbar. To configure a Port pin for analog input, set to 0 the corresponding
bit in register PnMDIN and disable the digital driver (PnMDOUT = 0 and Port Latch = 1). To force the crossbar to
skip a Port pin, set to 1 the corresponding bit in register PnSKIP.
Preliminary Rev 0.6
79
Analog-to-Digital Converter (ADC0)
C8051F85x/86x
Analog-to-Digital Converter (ADC0)
C8051F85x/86x
14.2. ADC Operation
The ADC is clocked by an adjustable conversion clock (SARCLK). SARCLK is a divided version of the selected
system clock when burst mode is disabled (ADBMEN = 0), or a divided version of the high-frequency oscillator
when burst mode is enabled (ADBMEN = 1). The clock divide value is determined by the ADSC bits in the ADC0CF
register. In most applications, SARCLK should be adjusted to operate as fast as possible, without exceeding the
maximum electrical specifications. The SARCLK does not directly determine sampling times or sampling rates.
14.2.1. Starting a Conversion
A conversion can be initiated in many ways, depending on the programmed states of the ADC0 Start of Conversion
Mode field (ADCM) in register ADC0CN0. Conversions may be initiated by one of the following:
1. Writing a 1 to the ADBUSY bit of register ADC0CN0 (software-triggered)
2. A timer overflow (see the ADC0CN0 register and the timer section for timer options)
3. A rising edge on the CNVSTR input signal (external pin-triggered)
Writing a 1 to ADBUSY provides software control of ADC0 whereby conversions are performed "on-demand". All
other trigger sources occur autonomous to code execution. When the conversion is complete, the ADC posts the
result to its output register and sets the ADC interrupt flag (ADINT). ADINT may be used to trigger a system
interrupts, if enabled, or polled by firmware.
During conversion, the ADBUSY bit is set to logic 1 and reset to logic 0 when the conversion is complete. However,
when polling for ADC conversion completions, the ADC0 interrupt flag (ADINT) should be used instead of the
ADBUSY bit. Converted data is available in the ADC0 data registers, ADC0H:ADC0L, when the conversion is
complete.
Important Note About Using CNVSTR: When the CNVSTR input is used as the ADC0 conversion source, the
associated port pin should be skipped in the crossbar settings.
14.2.2. Tracking Modes
Each ADC0 conversion must be preceded by a minimum tracking time in order for the converted result to be
accurate. The minimum tracking time is given in the electrical specifications tables. The ADTM bit in register
ADC0CN0 controls the ADC0 track-and-hold mode. In its default state when Burst Mode is disabled, the ADC0
input is continuously tracked, except when a conversion is in progress. A conversion will begin immediately when
the start-of-conversion trigger occurs.
When the ADTM bit is logic 1, each conversion is preceded by a tracking period of 4 SAR clocks (after the start-ofconversion signal) for any internal (non-CNVSTR) conversion trigger source. When the CNVSTR signal is used to
initiate conversions with ADTM set to 1, ADC0 tracks only when CNVSTR is low; conversion begins on the rising
edge of CNVSTR (see Figure 14.2). Setting ADTM to 1 is primarily useful when AMUX settings are frequently
changed and conversions are started using the ADBUSY bit.
80
Preliminary Rev 0.6
A. ADC0 Timing for External Trigger Source
CNVSTR
1
2
3
4
5
6
7
8
9 10 11 12 13 14
SAR Clocks
ADTM=1
ADTM=0
Low Power
or Convert
Track
Track or Convert
Convert
Low Power
Mode
Convert
Track
B. ADC0 Timing for Internal Trigger Source
Write '1' to ADBUSY,
Timer Overflow
1
SAR
Clocks
ADTM=1
Low Power
or Convert
ADTM=0
Track or
Convert
3
4
5
6
7
8
9 10 11 12 13 14 15 16 17 18
Track
1
SAR
Clocks
2
2
3
4
Convert
5
6
7
8
Low Power Mode
9 10 11 12 13 14
Convert
Track
Figure 14.2. 10-Bit ADC Track and Conversion Example Timing (ADBMEN = 0)
14.2.3. Burst Mode
Burst Mode is a power saving feature that allows ADC0 to remain in a low power state between conversions. When
Burst Mode is enabled, ADC0 wakes from a low power state, accumulates 1, 4, 8, 16, 32, or 64 samples using the
internal low-power high-frequency oscillator, then re-enters a low power state. Since the Burst Mode clock is
independent of the system clock, ADC0 can perform multiple conversions then enter a low power state within a
single system clock cycle, even if the system clock is slow (e.g. 80 kHz).
Burst Mode is enabled by setting ADBMEN to logic 1. When in Burst Mode, ADEN controls the ADC0 idle power
state (i.e. the state ADC0 enters when not tracking or performing conversions). If ADEN is set to logic 0, ADC0 is
powered down after each burst. If ADEN is set to logic 1, ADC0 remains enabled after each burst. On each convert
start signal, ADC0 is awakened from its Idle Power State. If ADC0 is powered down, it will automatically power up
and wait the programmable Power-Up Time controlled by the ADPWR bits. Otherwise, ADC0 will start tracking and
converting immediately. Figure 14.3 shows an example of Burst Mode Operation with a slow system clock and a
repeat count of 4.
When Burst Mode is enabled, a single convert start will initiate a number of conversions equal to the repeat count.
When Burst Mode is disabled, a convert start is required to initiate each conversion. In both modes, the ADC0 End
of Conversion Interrupt Flag (ADINT) will be set after “repeat count” conversions have been accumulated. Similarly,
the Window Comparator will not compare the result to the greater-than and less-than registers until “repeat count”
conversions have been accumulated.
In Burst Mode, tracking is determined by the settings in ADPWR and ADTK. Settling time requirements may need
adjustment in some applications. Refer to “14.2.4. Settling Time Requirements” on page 82 for more details.
Preliminary Rev 0.6
81
Analog-to-Digital Converter (ADC0)
C8051F85x/86x
Analog-to-Digital Converter (ADC0)
C8051F85x/86x
Notes:
Setting
ADTM to 1 will insert an additional 4 SAR clocks of tracking before each conversion, regardless of
the settings of ADPWR and ADTK.
When using Burst Mode, care must be taken to issue a convert start signal no faster than once every four
SYSCLK periods. This includes external convert start signals. The ADC will ignore convert start signals
which arrive before a burst is finished.
S yste m C lo ck
C o n ve rt S ta rt
ADTM = 1
ADEN = 0
P o w e re d
Down
P o w e r-U p
a n d T ra ck
T
4
ADTM = 0
ADEN = 0
P o w e re d
Down
P o w e r-U p
a n d T ra ck
C
C
T
T
C
T
4
C
T
T
C
ADPW R
T
4
T
C
C
T
T
4
C
P o w e re d
Down
P o w e re d
Down
P o w e r-U p
a n d T ra ck
T C ..
P o w e r-U p
a n d T ra ck
T C ..
ADTK
T = T ra ckin g se t b y A D T K
T 4 = T ra ckin g se t b y A D T M (4 S A R clo cks )
C = C o n ve rtin g
Figure 14.3. Burst Mode Tracking Example with Repeat Count Set to 4
14.2.4. Settling Time Requirements
A minimum amount of tracking time is required before each conversion can be performed, to allow the sampling
capacitor voltage to settle. This tracking time is determined by the AMUX0 resistance, the ADC0 sampling
capacitance, any external source resistance, and the accuracy required for the conversion. Note that when ADTM
is set to 1, four SAR clocks are used for tracking at the start of every conversion. Large external source impedance
will increase the required tracking time.
Figure 14.4 shows the equivalent ADC0 input circuit. The required ADC0 settling time for a given settling accuracy
(SA) may be approximated by Equation 14.1. When measuring any internal source, RTOTAL reduces to RMUX. See
the electrical specification tables for ADC0 minimum settling time requirements as well as the mux impedance and
sampling capacitor values.
n
2
t = ln  -------  R TOTAL C SAMPLE
SA
Equation 14.1. 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).
82
Preliminary Rev 0.6
MUX Select
P0.x
R MUX
C SAMPLE
RCInput= R MUX * C SAMPLE
Note: The value of CSAMPLE depends on the PGA Gain. See electrical specifications for details.
Figure 14.4. ADC0 Equivalent Input Circuits
14.2.5. Gain Setting
The ADC has gain settings of 1x and 0.5x. In 1x mode, the full scale reading of the ADC is determined directly by
VREF. In 0.5x mode, the full-scale reading of the ADC occurs when the input voltage is VREF x 2. The 0.5x gain
setting can be useful to obtain a higher input Voltage range when using a small VREF voltage, or to measure input
voltages that are between VREF and VDD. Gain settings for the ADC are controlled by the ADGN bit in register
ADC0CF. Note that even with a gain setting of 0.5, voltages above the supply rail cannot be measured directly by
the ADC.
14.3. 8-Bit Mode
Setting the ADC08BE bit in register ADC0CF to 1 will put the ADC in 8-bit mode.In 8-bit mode, only the 8 MSBs of
data are converted, allowing the conversion to be completed in fewer SAR clock cycles than a 10-bit conversion.
The two LSBs of a conversion are always 00 in this mode, and the ADC0L register will always read back 0x00.
14.4. 12-Bit Mode
When configured for 12-bit conversions, the ADC performs four 10-bit conversions using four different reference
voltages and combines the results into a single 12-bit value. Unlike simple averaging techniques, this method
provides true 12-bit resolution of AC or DC input signals without depending on noise to provide dithering. The
converter also employs a hardware dynamic element matching algorithm that reconfigures the largest elements of
the internal DAC for each of the four 10-bit conversions. This reconfiguration cancels any matching errors and
enables the converter to achieve 12-bit linearity performance to go along with its 12-bit resolution.
The 12-bit mode is enabled by setting the AD12BE bit in register ADC0AC to logic 1 and configuring the ADC in
burst mode (ADBMEN = 1) for four or more conversions. The conversion can be initiated using any of the
conversion start sources, and the 12-bit result will appear in the ADC0H and ADC0L registers. Since the 12-bit
result is formed from a combination of four 10-bit results, the maximum output value is 4 x (1023) = 4092, rather
than the max value of (2^12 – 1) = 4095 that is produced by a traditional 12-bit converter. To further increase
resolution, the burst mode repeat value may be configured to any multiple of four conversions. For example, if a
repeat value of 16 is selected, the ADC0 output will be a 14-bit number (sum of four 12-bit numbers) with 13
effective bits of resolution.
The AD12SM bit in register ADC0TK controls when the ADC will track and sample the input signal. When AD12SM
is set to 1, the selected input signal will be tracked before the first conversion of a set and held internally during all
four conversions. When AD12SM is cleared to 0, the ADC will track and sample the selected input before each of
the four conversions in a set. When maximum throughput (180-200 ksps) is needed, it is recommended that
AD12SM be set to 1 and ADTK to 0x3F, and that the ADC be placed in always-on mode (ADEN = 1). For sample
rates under 180 ksps, or when accumulating multiple samples, AD12SM should normally be cleared to 0, and
ADTK should be configured to provide the appropriate settling time for the subsequent conversions.
Preliminary Rev 0.6
83
Analog-to-Digital Converter (ADC0)
C8051F85x/86x
Analog-to-Digital Converter (ADC0)
C8051F85x/86x
14.5. Power Considerations
The ADC has several power-saving features which can help the user optimize power consumption according to the
needs of the application. The most efficient way to use the ADC for slower sample rates is by using burst mode.
Burst mode dynamically controls power to the ADC and (if used) the internal voltage reference. By completely
powering off these circuits when the ADC is not tracking or converting, the average supply current required for
lower sampling rates is reduced significantly.
The ADC also provides low power options that allow reduction in operating current when operating at low SAR
clock frequencies or with longer tracking times. The internal common-mode buffer can be configured for low power
mode by setting the ADLPM bit in ADC0PWR to 1. Two other fields in the ADC0PWR register (ADBIAS and
ADMXLP) may be used together to adjust the power consumed by the ADC and its multiplexer and reference
buffers, respectively. In general, these options are used together, when operating with a SAR conversion clock
frequency of 4 MHz.
Table 14.2. ADC0 Optimal Power Configuration (8 and 10-bit Mode)
Required
Throughput
Reference Source Mode Configuration
SAR Clock Speed
Other Register Field
Settings
325-800 ksps
Any
Always-On
(ADEN = 1
ADBMEN = 0)
12.25 MHz
(ADSC = 1)
ADC0PWR = 0x40
ADC0TK = N/A
ADRPT = 0
0-325 ksps
External
Burst Mode
(ADEN = 0
ADBMEN = 1)
12.25 MHz
(ADSC = 1)
ADC0PWR = 0x44
ADC0TK = 0x3A
ADRPT = 0
250-325 ksps
Internal
Burst Mode
(ADEN = 0
ADBMEN = 1)
12.25 MHz
(ADSC = 1)
ADC0PWR = 0x44
ADC0TK = 0x3A
ADRPT = 0
200-250 ksps
Internal
Always-On
(ADEN = 1
ADBMEN = 0)
4.08 MHz
(ADSC = 5)
ADC0PWR = 0xF0
ADC0TK = N/A
ADRPT = 0
0-200 ksps
Internal
Burst Mode
(ADEN = 0
ADBMEN = 1)
4.08 MHz
(ADSC = 5)
ADC0PWR = 0xF4
ADC0TK = 0x34
ADRPT = 0
Notes:
1. For always-on configuration, ADSC settings assume SYSCLK is the internal 24.5 MHz high-frequency oscillator.
Adjust ADSC as needed if using a different source for SYSCLK.
2. ADRPT reflects the minimum setting for this bit field. When using the ADC in Burst Mode, up to 64 samples may be
auto-accumulated per conversion start by adjusting ADRPT.
84
Preliminary Rev 0.6
Table 14.3. ADC0 Optimal Power Configuration (12-bit Mode)
Required
Throughput
Reference Source Mode Configuration
SAR Clock Speed
Other Register Field
Settings
Any
Always-On +
Burst Mode
(ADEN = 1
ADBMEN = 1)
12.25 MHz
(ADSC = 1)
ADC0PWR = 0x40
ADC0TK = 0xBF
ADRPT = 1
125-180 ksps
Any
Always-On +
Burst Mode
(ADEN = 1
ADBMEN = 1)
12.25 MHz
(ADSC = 1)
ADC0PWR = 0x40
ADC0TK = 0x3A
ADRPT = 1
0-125 ksps
External
Burst Mode
(ADEN = 0
ADBMEN = 1)
12.25 MHz
(ADSC = 1)
ADC0PWR = 0x44
ADC0TK = 0x3A
ADRPT = 1
50-125 ksps
Internal
Burst Mode
(ADEN = 0
ADBMEN = 1)
12.25 MHz
(ADSC = 1)
ADC0PWR = 0x44
ADC0TK = 0x3A
ADRPT = 1
0-50 ksps
Internal
Burst Mode
(ADEN = 0
ADBMEN = 1)
4.08 MHz
(ADSC = 5)
ADC0PWR = 0xF4
ADC0TK = 0x34
ADRPT = 1
180-200 ksps
Notes:
1. ADRPT reflects the minimum setting for this bit field. When using the ADC in Burst Mode, up to 64 samples may be
auto-accumulated per conversion trigger by adjusting ADRPT.
For applications where burst mode is used to automatically accumulate multiple results, additional supply current
savings can be realized. The length of time the ADC is active during each burst contains power-up time at the
beginning of the burst as well as the conversion time required for each conversion in the burst. The power-on time
is only required at the beginning of each burst. When compared with single-sample bursts to collect the same
number of conversions, multi-sample bursts will consume significantly less power. For example, performing an
eight-cycle burst of 10-bt conversions consumes about 61% of the power required to perform those same eight
samples in single-cycle bursts. For 12-bit conversions, an eight-cycle burst results in about 85% of the equivalent
single-cycle bursts. Figure 14.5 shows this relationship for the different burst cycle lengths.
See the Electrical Characteristics chapter for details on power consumption and the maximum clock frequencies
allowed in each mode.
Preliminary Rev 0.6
85
Analog-to-Digital Converter (ADC0)
C8051F85x/86x
10ͲBitBurstModePower
12ͲBitBurstModePower
100%
100%
AverageCurrentComparedtoSingleͲCycle
AverageCurrentComparedtoSingleͲCycle
Analog-to-Digital Converter (ADC0)
C8051F85x/86x
95%
90%
85%
80%
75%
70%
65%
60%
55%
50%
98%
96%
94%
92%
90%
88%
86%
84%
82%
80%
1
2
4
8
16
32
64
1
NumberofCyclesAccumulatedinBurst
2
4
8
16
NumberofCyclesAccumulatedinBurst
Figure 14.5. Burst Mode Accumulation Power Savings
14.6. Output Code Formatting
The registers ADC0H and ADC0L contain the high and low bytes of the output conversion code from the ADC at
the completion of each conversion. Data can be right-justified or left-justified, depending on the setting of the
ADSJST field. When the repeat count is set to 1 in 10-bit mode, conversion codes are represented as 10-bit
unsigned integers. Inputs are measured from 0 to VREF x 1023/1024. Example codes are shown below for both
right-justified and left-justified data. Unused bits in the ADC0H and ADC0L registers are set to 0.
Input Voltage
Right-Justified
Left-Justified
ADC0H:ADC0L (ADSJST = 000)
ADC0H:ADC0L (ADSJST = 100)
VREF x 1023/1024
0x03FF
0xFFC0
VREF x 512/1024
0x0200
0x8000
VREF x 256/1024
0x0100
0x4000
0
0x0000
0x0000
When the repeat count is greater than 1, the output conversion code represents the accumulated result of the
conversions performed and is updated after the last conversion in the series is finished. Sets of 4, 8, 16, 32, or 64
consecutive samples can be accumulated and represented in unsigned integer format. The repeat count can be
selected using the ADRPT bits in the ADC0AC register. When a repeat count higher than 1, the ADC output must
be right-justified (ADSJST = 0xx); unused bits in the ADC0H and ADC0L registers are set to 0. The example below
shows the right-justified result for various input voltages and repeat counts. Notice that accumulating 2n samples is
equivalent to left-shifting by n bit positions when all samples returned from the ADC have the same value.
Input Voltage
Repeat Count = 4
Repeat Count = 16
Repeat Count = 64
VREF x 1023/1024
0x0FFC
0x3FF0
0xFFC0
VREF x 512/1024
0x0800
0x2000
0x8000
VREF x 511/1024
0x07FC
0x1FF0
0x7FC0
0
0x0000
0x0000
0x0000
The ADSJST bits can be used to format the contents of the 16-bit accumulator. The accumulated result can be
shifted right by 1, 2, or 3 bit positions. Based on the principles of oversampling and averaging, the effective ADC
resolution increases by 1 bit each time the oversampling rate is increased by a factor of 4. The example below
shows how to increase the effective ADC resolution by 1, 2, and 3 bits to obtain an effective ADC resolution of 11bit, 12-bit, or 13-bit respectively without CPU intervention.
86
Preliminary Rev 0.6
Input Voltage
Repeat Count = 4
Repeat Count = 16
Repeat Count = 64
Shift Right = 1
Shift Right = 2
Shift Right = 3
11-Bit Result
12-Bit Result
13-Bit Result
VREF x 1023/1024
VREF x 511/1024
0x07F7
0x0FFC
0x1FF8
VREF x 512/1024
0x0400
0x0800
0x1000
0x03FE
0x04FC
0x0FF8
0
0x0000
0x0000
0x0000
14.7. Programmable Window Detector
The ADC Programmable Window Detector continuously compares the ADC0 output registers to user-programmed
limits, and notifies the system when a desired condition is detected. This is especially effective in an interruptdriven system, saving code space and CPU bandwidth while delivering faster system response times. The window
detector interrupt flag (ADWINT in register ADC0CN0) can also be used in polled mode. The ADC0 Greater-Than
(ADC0GTH, ADC0GTL) and Less-Than (ADC0LTH, ADC0LTL) registers hold the comparison values. The window
detector flag can be programmed to indicate when measured data is inside or outside of the user-programmed
limits, depending on the contents of the ADC0 Less-Than and ADC0 Greater-Than registers.
14.7.1. Window Detector In Single-Ended Mode
Figure 14.6 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 ADWINT 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
ADWINT 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 14.7 shows an example
using left-justified data with the same comparison values.
ADC0H:ADC0L
ADC0H:ADC0L
Input Voltage
(Px.x - GND)
VREF x (1023/
1024)
Input Voltage
(Px.x - GND)
VREF x (1023/
1024)
0x03FF
0x03FF
ADWINT
not affected
ADWINT=1
0x0081
VREF x (128/1024)
VREF x (64/1024)
0x0080
0x007F
0x0041
0x0040
0x0081
ADC0LTH:ADC0LTL
VREF x (128/1024)
ADWINT=1
ADC0GTH:ADC0GTL
VREF x (64/1024)
0x003F
0x0080
0x007F
0x0041
0x0040
ADC0GTH:ADC0GTL
ADWINT
not affected
ADC0LTH:ADC0LTL
0x003F
ADWINT=1
ADWINT
not affected
0
0x0000
0
0x0000
Figure 14.6. ADC Window Compare Example: Right-Justified Single-Ended Data
Preliminary Rev 0.6
87
Analog-to-Digital Converter (ADC0)
C8051F85x/86x
Analog-to-Digital Converter (ADC0)
C8051F85x/86x
ADC0H:ADC0L
ADC0H:ADC0L
Input Voltage
(Px.x - GND)
VREF x (1023/
1024)
Input Voltage
(Px.x - GND)
VREF x (1023/
1024)
0xFFC0
0xFFC0
ADWINT
not affected
ADWINT=1
0x2040
VREF x (128/1024)
0x2000
0x1FC0
0x2040
ADC0LTH:ADC0LTL
ADWINT=1
0x1040
VREF x (64/1024)
0x1000
VREF x (128/1024)
ADC0GTH:ADC0GTL
0x2000
0x1FC0
0x1040
VREF x (64/1024)
0x0FC0
0x1000
ADC0GTH:ADC0GTL
ADWINT
not affected
ADC0LTH:ADC0LTL
0x0FC0
ADWINT=1
ADWINT
not affected
0
0x0000
0
0x0000
Figure 14.7. ADC Window Compare Example: Left-Justified Single-Ended Data
88
Preliminary Rev 0.6
14.8. Voltage and Ground Reference Options
The voltage reference multiplexer is configurable to use an externally connected voltage reference, the internal
voltage reference, or one of two power supply voltages. The ground reference mux allows the ground reference for
ADC0 to be selected between the ground pin (GND) or a port pin dedicated to analog ground (AGND).
The voltage and ground reference options are configured using the REF0CN register.
Important Note About the VREF and AGND Inputs: Port pins are used as the external VREF and AGND inputs.
When using an external voltage reference, VREF should be configured as an analog input and skipped by the
digital crossbar. When using AGND as the ground reference to ADC0, AGND should be configured as an analog
input and skipped by the Digital Crossbar.
14.8.1. External Voltage Reference
To use an external voltage reference, REFSL should be set to 00. Bypass capacitors should be added as
recommended by the manufacturer of the external voltage reference. If the manufacturer does not provide
recommendations, a 4.7uF in parallel with a 0.1uF capacitor is recommended.
14.8.2. Internal Voltage Reference
For applications requiring the maximum number of port I/O pins, or very short VREF turn-on time, the high-speed
reference will be the best internal reference option to choose. The internal reference is selected by setting REFSL
to 11. When selected, the internal reference will be automatically enabled/disabled on an as-needed basis by the
ADC. The reference can be set to one of two voltage values: 1.65 V or 2.4 V, depending on the value of the
IREFLVL bit.
For applications with a non-varying power supply voltage, using the power supply as the voltage reference can
provide the ADC with added dynamic range at the cost of reduced power supply noise rejection. To use the
external supply pin (VDD) or the 1.8 V regulated digital supply voltage as the reference source, REFSL should be
set to 01 or 10, respectively.
Internal reference sources are not routed to the VREF pin, and do not require external capacitors. The electrical
specifications tables detail SAR clock and throughput limitations for each reference source.
14.8.3. Analog Ground Reference
To prevent ground noise generated by switching digital logic from affecting sensitive analog measurements, a
separate analog ground reference option is available. When enabled, the ground reference for the ADC during
both the tracking/sampling and the conversion periods is taken from the AGND pin. Any external sensors sampled
by the ADC should be referenced to the AGND pin. If an external voltage reference is used, the AGND pin should
be connected to the ground of the external reference and its associated decoupling capacitor. The separate analog
ground reference option is enabled by setting GNDSL to 1. Note that when sampling the internal temperature
sensor, the internal chip ground is always used for the sampling operation, regardless of the setting of the GNDSL
bit. Similarly, whenever the internal 1.65 V high-speed reference is selected, the internal chip ground is always
used during the conversion period, regardless of the setting of the GNDSL bit.
Preliminary Rev 0.6
89
Analog-to-Digital Converter (ADC0)
C8051F85x/86x
14.9. Temperature Sensor
An on-chip temperature sensor is included, which can be directly accessed via the ADC multiplexer in single-ended
configuration. To use the ADC to measure the temperature sensor, the ADC mux channel should select the
temperature sensor. The temperature sensor transfer function is shown in Figure 14.8. The output voltage (VTEMP)
is the positive ADC input when the ADC multiplexer is set correctly. The TEMPE bit in register REF0CN enables/
disables the temperature sensor. 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 the electrical
specification tables for the slope and offset parameters of the temperature sensor.
VTEMP = (Slope x TempC) + Offset
TempC = (VTEMP - Offset) / Slope
Voltage
Analog-to-Digital Converter (ADC0)
C8051F85x/86x
Slope (V / deg C)
Offset (V at 0 Celsius)
Temperature
Figure 14.8. Temperature Sensor Transfer Function
14.9.1. Calibration
The uncalibrated temperature sensor output is extremely linear and suitable for relative temperature
measurements. For absolute temperature measurements, offset and/or gain calibration is recommended. Typically
a 1-point (offset) calibration includes the following steps:
1. Control/measure the ambient temperature (this temperature must be known).
2. Power the device, and delay for a few seconds to allow for self-heating.
3. Perform an ADC conversion with the temperature sensor selected as the ADC input.
4. Calculate the offset characteristics, and store this value in non-volatile memory for use with subsequent
temperature sensor measurements.
90
Preliminary Rev 0.6
14.10. ADC Control Registers
Register 14.1. ADC0CN0: ADC0 Control 0
Bit
7
6
5
4
3
2
Name
ADEN
ADBMEN
ADINT
ADBUSY
ADWINT
ADCM
Type
RW
RW
RW
RW
RW
RW
Reset
0
0
0
0
0
0
1
0
0
0
SFR Address: 0xE8 (bit-addressable)
Table 14.4. ADC0CN0 Register Bit Descriptions
Bit
Name
7
ADEN
Function
Enable.
0: ADC0 Disabled (low-power shutdown).
1: ADC0 Enabled (active and ready for data conversions).
6
ADBMEN
Burst Mode Enable.
0: ADC0 Burst Mode Disabled.
1: ADC0 Burst Mode Enabled.
5
ADINT
Conversion Complete Interrupt Flag.
Set by hardware upon completion of a data conversion (ADBMEN=0), or a burst of conversions (ADBMEN=1). Can trigger an interrupt. Must be cleared by software.
4
ADBUSY
ADC Busy.
Writing 1 to this bit initiates an ADC conversion when ADC0CM = 000. This bit should not
be polled to indicate when a conversion is complete. Instead, the ADINT bit should be
used when polling for conversion completion.
3
ADWINT
Window Compare Interrupt Flag.
Set by hardware when the contents of ADC0H:ADC0L fall within the window specified by
ADC0GTH:ADC0GTL and ADC0LTH:ADC0LTL. Can trigger an interrupt. Must be
cleared by software.
2:0
ADCM
Start of Conversion Mode Select.
Specifies the ADC0 start of conversion source. All remaining bit combinations are
reserved.
000: ADC0 conversion initiated on write of 1 to ADBUSY.
001: ADC0 conversion initiated on overflow of Timer 0.
010: ADC0 conversion initiated on overflow of Timer 2.
011: ADC0 conversion initiated on overflow of Timer 3.
100: ADC0 conversion initiated on rising edge of CNVSTR.
101-111: Reserved.
Preliminary Rev 0.6
91
Analog-to-Digital Converter (ADC0)
C8051F85x/86x
Analog-to-Digital Converter (ADC0)
C8051F85x/86x
Register 14.2. ADC0CN1: ADC0 Control 1
Bit
7
6
5
4
3
2
1
0
Name
Reserved
ADCMBE
Type
R
RW
Reset
0
0
0
0
0
0
0
0
SFR Address: 0xB2
Table 14.5. ADC0CN1 Register Bit Descriptions
Bit
Name
Function
7:1
Reserved
Must write reset value.
0
ADCMBE
Common Mode Buffer Enable.
0: Disable the common mode buffer. This setting should be used only if the tracking time
of the signal is greater than 1.5 us.
1: Enable the common mode buffer. This setting should be used in most cases, and will
give the best dynamic ADC performance. The common mode buffer must be enabled if
signal tracking time is less than or equal to 1.5 us.
92
Preliminary Rev 0.6
Register 14.3. ADC0CF: ADC0 Configuration
Bit
7
6
5
4
3
2
1
0
Name
ADSC
AD8BE
ADTM
ADGN
Type
RW
RW
RW
RW
0
0
0
Reset
1
1
1
1
1
SFR Address: 0xBC
Table 14.6. ADC0CF Register Bit Descriptions
Bit
Name
7:3
ADSC
Function
SAR Clock Divider.
This field sets the ADC clock divider value. It should be configured to be as close to the
maximum SAR clock speed as the datasheet will allow. The SAR clock frequency is
given by the following equation:
F ADCCLK
F CLKSAR = ------------------------ADSC + 1
FADCCLK is equal to the selected SYSCLK when ADBMEN is 0 and the high-frequency
oscillator when ADBMEN is 1.
2
AD8BE
8-Bit Mode Enable.
0: ADC0 operates in 10-bit or 12-bit mode (normal operation).
1: ADC0 operates in 8-bit mode.
1
ADTM
Track Mode.
Selects between Normal or Delayed Tracking Modes.
0: Normal Track Mode. When ADC0 is enabled, conversion begins immediately following
the start-of-conversion signal.
1: Delayed Track Mode. When ADC0 is enabled, conversion begins 4 SAR clock cycles
following the start-of-conversion signal. The ADC is allowed to track during this time.
0
ADGN
Gain Control.
0: The on-chip PGA gain is 0.5.
1: The on-chip PGA gain is 1.
Preliminary Rev 0.6
93
Analog-to-Digital Converter (ADC0)
C8051F85x/86x
Analog-to-Digital Converter (ADC0)
C8051F85x/86x
Register 14.4. ADC0AC: ADC0 Accumulator Configuration
Bit
7
6
5
Name
AD12BE
ADAE
ADSJST
ADRPT
Type
RW
RW
RW
RW
Reset
0
0
0
4
3
0
0
2
0
1
0
0
0
SFR Address: 0xB3
Table 14.7. ADC0AC Register Bit Descriptions
Bit
Name
7
AD12BE
Function
12-Bit Mode Enable.
Enables 12-bit Mode. In 12-bit mode, the ADC throughput is reduced by a factor of 4.
0: 12-bit Mode Disabled.
1: 12-bit Mode Enabled.
6
ADAE
Accumulate Enable.
Enables multiple conversions to be accumulated when burst mode is disabled.
0: ADC0H:ADC0L contain the result of the latest conversion when Burst Mode is disabled.
1: ADC0H:ADC0L contain the accumulated conversion results when Burst Mode is disabled. Software must write 0x0000 to ADC0H:ADC0L to clear the accumulated result.
5:3
ADSJST
Accumulator Shift and Justify.
Specifies the format of data read from ADC0H:ADC0L. All remaining bit combinations
are reserved.
000: Right justified. No shifting applied.
001: Right justified. Shifted right by 1 bit.
010: Right justified. Shifted right by 2 bits.
011: Right justified. Shifted right by 3 bits.
100: Left justified. No shifting applied.
101-111: Reserved.
2:0
ADRPT
Repeat Count.
Selects the number of conversions to perform and accumulate in Burst Mode. This bit
field must be set to 000 if Burst Mode is disabled.
000: Perform and Accumulate 1 conversion (not used in 12-bit mode).
001: Perform and Accumulate 4 conversions (1 conversion in 12-bit mode).
010: Perform and Accumulate 8 conversions (2 conversions in 12-bit mode).
011: Perform and Accumulate 16 conversions (4 conversions in 12-bit mode).
100: Perform and Accumulate 32 conversions (8 conversions in 12-bit mode).
101: Perform and Accumulate 64 conversions (16 conversions in 12-bit mode).
110-111: Reserved.
94
Preliminary Rev 0.6
Register 14.5. ADC0PWR: ADC0 Power Control
Bit
7
6
5
4
3
2
Name
ADBIAS
ADMXLP
ADLPM
ADPWR
Type
RW
RW
RW
RW
0
0
Reset
0
0
1
1
1
0
1
1
SFR Address: 0xDF
Table 14.8. ADC0PWR Register Bit Descriptions
Bit
Name
7:6
ADBIAS
Function
Bias Power Select.
This field can be used to adjust the ADC's power consumption based on the conversion
speed. Higher bias currents allow for faster conversion times.
00: Select bias current mode 0. Recommended to use modes 1, 2, or 3.
01: Select bias current mode 1 (SARCLK <= 16 MHz).
10: Select bias current mode 2.
11: Select bias current mode 3 (SARCLK <= 4 MHz).
5
ADMXLP
Mux and Reference Low Power Mode Enable.
Enables low power mode operation for the multiplexer and voltage reference buffers.
0: Low power mode disabled.
1: Low power mode enabled (SAR clock < 4 MHz).
4
ADLPM
Low Power Mode Enable.
This bit can be used to reduce power to the ADC's internal common mode buffer. It can
be set to 1 to reduce power when tracking times in the application are longer (slower
sample rates).
0: Disable low power mode.
1: Enable low power mode (requires extended tracking time).
3:0
ADPWR
Burst Mode Power Up Time.
This field sets the time delay allowed for the ADC to power up from a low power state.
When ADTM is set, an additional 4 SARCLKs are added to this time.
8  ADPWR
T PWRTIME = -----------------------------F HFOSC
Preliminary Rev 0.6
95
Analog-to-Digital Converter (ADC0)
C8051F85x/86x
Analog-to-Digital Converter (ADC0)
C8051F85x/86x
Register 14.6. ADC0TK: ADC0 Burst Mode Track Time
Bit
7
6
5
4
Name
AD12SM
Reserved
ADTK
Type
RW
RW
RW
Reset
0
0
0
3
1
1
2
1
0
1
1
0
SFR Address: 0xB9
Table 14.9. ADC0TK Register Bit Descriptions
Bit
Name
7
AD12SM
Function
12-Bit Sampling Mode.
This bit controls the way that the ADC samples the input when in 12-bit mode. When the
ADC is configured for multiple 12-bit conversions in burst mode, the AD12SM bit should
be cleared to 0.
0: The ADC will re-track and sample the input four times during a 12-bit conversion.
1: The ADC will sample the input once at the beginning of each 12-bit conversion. The
ADTK field can be set to 63 to maximize throughput.
6
Reserved
5:0
ADTK
Must write reset value.
Burst Mode Tracking Time.
This field sets the time delay between consecutive conversions performed in Burst
Mode. When ADTM is set, an additional 4 SARCLKs are added to this time.
64 – ADTK
T BMTK = ---------------------------F HFOSC
The Burst Mode track delay is not inserted prior to the first conversion. The required
tracking time for the first conversion should be defined with the ADPWR field.
96
Preliminary Rev 0.6
Register 14.7. ADC0H: ADC0 Data Word High Byte
Bit
7
6
5
4
Name
ADC0H
Type
RW
Reset
0
0
0
0
3
2
1
0
0
0
0
0
SFR Address: 0xBE
Table 14.10. ADC0H Register Bit Descriptions
Bit
Name
7:0
ADC0H
Function
Data Word High Byte.
When read, this register returns the most significant byte of the 16-bit ADC0 accumulator, formatted according to the settings in ADSJST. The register may also be written, to
set the upper byte of the 16-bit ADC0 accumulator.
Note: If Accumulator shifting is enabled, the most significant bits of the value read will be zeros. This register should not be
written when the SYNC bit is set to 1.
Preliminary Rev 0.6
97
Analog-to-Digital Converter (ADC0)
C8051F85x/86x
Analog-to-Digital Converter (ADC0)
C8051F85x/86x
Register 14.8. ADC0L: ADC0 Data Word Low Byte
Bit
7
6
5
4
Name
ADC0L
Type
RW
Reset
0
0
0
0
3
2
1
0
0
0
0
0
SFR Address: 0xBD
Table 14.11. ADC0L Register Bit Descriptions
Bit
Name
7:0
ADC0L
Function
Data Word Low Byte.
When read, this register returns the least significant byte of the 16-bit ADC0 accumulator, formatted according to the settings in ADSJST. The register may also be written, to
set the lower byte of the 16-bit ADC0 accumulator.
Note: If Accumulator shifting is enabled, the most significant bits of the value read will be zeros. This register should not be
written when the SYNC bit is set to 1.
98
Preliminary Rev 0.6
Register 14.9. ADC0GTH: ADC0 Greater-Than High Byte
Bit
7
6
5
4
Name
ADC0GTH
Type
RW
Reset
1
1
1
1
3
2
1
0
1
1
1
1
SFR Address: 0xC4
Table 14.12. ADC0GTH Register Bit Descriptions
Bit
Name
7:0
ADC0GTH
Function
Greater-Than High Byte.
Most Significant Byte of the 16-bit Greater-Than window compare register.
Preliminary Rev 0.6
99
Analog-to-Digital Converter (ADC0)
C8051F85x/86x
Analog-to-Digital Converter (ADC0)
C8051F85x/86x
Register 14.10. ADC0GTL: ADC0 Greater-Than Low Byte
Bit
7
6
5
4
Name
ADC0GTL
Type
RW
Reset
1
1
1
1
3
2
1
0
1
1
1
1
SFR Address: 0xC3
Table 14.13. ADC0GTL Register Bit Descriptions
Bit
Name
7:0
ADC0GTL
Function
Greater-Than Low Byte.
Least Significant Byte of the 16-bit Greater-Than window compare register.
Note: In 8-bit mode, this register should be set to 0x00.
100
Preliminary Rev 0.6
Register 14.11. ADC0LTH: ADC0 Less-Than High Byte
Bit
7
6
5
4
Name
ADC0LTH
Type
RW
Reset
0
0
0
0
3
2
1
0
0
0
0
0
SFR Address: 0xC6
Table 14.14. ADC0LTH Register Bit Descriptions
Bit
Name
7:0
ADC0LTH
Function
Less-Than High Byte.
Most Significant Byte of the 16-bit Less-Than window compare register.
Preliminary Rev 0.6
101
Analog-to-Digital Converter (ADC0)
C8051F85x/86x
Analog-to-Digital Converter (ADC0)
C8051F85x/86x
Register 14.12. ADC0LTL: ADC0 Less-Than Low Byte
Bit
7
6
5
4
Name
ADC0LTL
Type
RW
Reset
0
0
0
0
3
2
1
0
0
0
0
0
SFR Address: 0xC5
Table 14.15. ADC0LTL Register Bit Descriptions
Bit
Name
7:0
ADC0LTL
Function
Less-Than Low Byte.
Least Significant Byte of the 16-bit Less-Than window compare register.
Note: In 8-bit mode, this register should be set to 0x00.
102
Preliminary Rev 0.6
Register 14.13. ADC0MX: ADC0 Multiplexer Selection
Bit
7
6
5
4
3
2
Name
Reserved
ADC0MX
Type
R
RW
Reset
0
0
0
1
1
1
1
0
1
1
SFR Address: 0xBB
Table 14.16. ADC0MX Register Bit Descriptions
Bit
Name
Function
7:5
Reserved
Must write reset value.
4:0
ADC0MX
AMUX0 Positive Input Selection.
Selects the positive input channel for ADC0. For reserved bit combinations, no input is
selected.
00000: ADC0.0
00001: ADC0.1
00010: ADC0.2
00011: ADC0.3
00100: ADC0.4
00101: ADC0.5
00110: ADC0.6
00111: ADC0.7
01000: ADC0.8
01001: ADC0.9
01010: ADC0.10
01011: ADC0.11
01100: ADC0.12
01101: ADC0.13
01110: ADC0.14
01111: ADC0.15
10000: Temperature sensor.
10001: Internal LDO regulator output.
10010: VDD
10011: GND
10100-11111: Reserved.
Preliminary Rev 0.6
103
Analog-to-Digital Converter (ADC0)
C8051F85x/86x
Analog-to-Digital Converter (ADC0)
C8051F85x/86x
Register 14.14. REF0CN: Voltage Reference Control
Bit
7
6
5
4
3
Name
IREFLVL
Reserved
GNDSL
REFSL
TEMPE
Reserved
Type
RW
R
RW
RW
RW
R
Reset
0
0
0
1
2
1
0
1
0
0
SFR Address: 0xD1
Table 14.17. REF0CN Register Bit Descriptions
Bit
Name
7
IREFLVL
Function
Internal Voltage Reference Level.
Sets the voltage level for the internal reference source.
0: The internal reference operates at 1.65 V nominal.
1: The internal reference operates at 2.4 V nominal.
6
Reserved
5
GNDSL
Must write reset value.
Analog Ground Reference.
Selects the ADC0 ground reference.
0: The ADC0 ground reference is the GND pin.
1: The ADC0 ground reference is the AGND pin.
4:3
REFSL
Voltage Reference Select.
Selects the ADC0 voltage reference.
00: The ADC0 voltage reference is the VREF pin.
01: The ADC0 voltage reference is the VDD pin.
10: The ADC0 voltage reference is the internal 1.8 V digital supply voltage.
11: The ADC0 voltage reference is the internal voltage reference.
2
TEMPE
Temperature Sensor Enable.
Enables/Disables the internal temperature sensor.
0: Temperature Sensor Disabled.
1: Temperature Sensor Enabled.
1:0
104
Reserved
Must write reset value.
Preliminary Rev 0.6
0
15. CIP-51 Microcontroller Core
The C8051F85x/86x uses 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 software. The MCU family has a
superset of all the peripherals included with a standard 8051. The CIP-51 also includes on-chip debug hardware
and interfaces directly with the analog and digital subsystems providing a complete data acquisition or controlsystem solution in a single integrated 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 15.1 for a block diagram). The CIP-51
includes the following features:
Fully
Reset
25
Compatible with MCS-51 Instruction Set
MIPS Peak Throughput with 25 MHz Clock
0 to 25 MHz Clock Frequency
Extended Interrupt Handler
Power
Input
Management Modes
On-chip Debug Logic
Program and Data Memory Security
15.1. Performance
The CIP-51 employs a pipelined architecture that greatly increases its instruction throughput over the standard
8051 architecture. 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.
D8
TMP2
B REGISTER
STACK POINTER
SRAM
ADDRESS
REGISTER
PSW
D8
D8
D8
ALU
SRAM
D8
D8
TMP1
ACCUMULATOR
D8
D8
D8
DATA BUS
DATA BUS
DATA BUS
SFR_ADDRESS
BUFFER
D8
DATA POINTER
D8
D8
SFR
BUS
INTERFACE
SFR_CONTROL
SFR_WRITE_DATA
SFR_READ_DATA
PC INCREMENTER
DATA BUS
CIP-51 Microcontroller Core
C8051F85x/86x
PROGRAM COUNTER (PC)
PRGM. ADDRESS REG.
PIPELINE
RESET
CLOCK
STOP
IDLE
MEM_ADDRESS
D8
A16
MEMORY
INTERFACE
MEM_CONTROL
MEM_WRITE_DATA
MEM_READ_DATA
D8
CONTROL
LOGIC
SYSTEM_IRQs
D8
POWER CONTROL
REGISTER
INTERRUPT
INTERFACE
EMULATION_IRQ
D8
Figure 15.1. CIP-51 Block Diagram
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 execution time.
106
Clocks to Execute
1
2
2/3
3
3/4
4
4/5
5
8
Number of Instructions
26
50
5
14
7
3
1
2
1
Preliminary Rev 0.6
15.2. Programming and Debugging Support
In-system programming of the flash program memory and communication with on-chip debug support logic is
accomplished via the Silicon Labs 2-Wire Development Interface (C2).
The on-chip debug support logic facilitates full speed in-circuit debugging, allowing the setting of hardware
breakpoints, starting, stopping and single stepping through program execution (including interrupt service
routines), examination of the program's call stack, and reading/writing the contents of registers and memory. This
method of on-chip debugging is completely non-intrusive, requiring no RAM, Stack, timers, or other on-chip
resources.
The CIP-51 is supported by development tools from Silicon Labs and third party vendors. Silicon Labs provides an
integrated development environment (IDE) including editor, debugger and programmer. The IDE's debugger and
programmer interface to the CIP-51 via the C2 interface to provide fast and efficient in-system device programming
and debugging. Third party macro assemblers and C compilers are also available.
15.3. Instruction Set
The instruction set of the CIP-51 System Controller is fully compatible with the standard MCS-51™ instruction 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 standard 8051.
15.3.1. 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 15.1 is the CIP-51 Instruction Set
Summary, which includes the mnemonic, number of bytes, and number of clock cycles for each instruction.
Preliminary Rev 0.6
107
CIP-51 Microcontroller Core
C8051F85x/86x
CIP-51 Microcontroller Core
C8051F85x/86x
Table 15.1. CIP-51 Instruction Set Summary
Mnemonic
Description
Bytes
Clock
Cycles
Arithmetic Operations
ADD A, Rn
Add register to A
1
1
ADD A, direct
Add direct byte to A
2
2
ADD A, @Ri
Add indirect RAM to A
1
2
ADD A, #data
Add immediate to A
2
2
ADDC A, Rn
Add register to A with carry
1
1
ADDC A, direct
Add direct byte to A with carry
2
2
ADDC A, @Ri
Add indirect RAM to A with carry
1
2
ADDC A, #data
Add immediate to A with carry
2
2
SUBB A, Rn
Subtract register from A with borrow
1
1
SUBB A, direct
Subtract direct byte from A with borrow
2
2
SUBB A, @Ri
Subtract indirect RAM from A with borrow
1
2
SUBB A, #data
Subtract immediate from A with borrow
2
2
INC A
Increment A
1
1
INC Rn
Increment register
1
1
INC direct
Increment direct byte
2
2
INC @Ri
Increment indirect RAM
1
2
DEC A
Decrement A
1
1
DEC Rn
Decrement register
1
1
DEC direct
Decrement direct byte
2
2
DEC @Ri
Decrement indirect RAM
1
2
INC DPTR
Increment Data Pointer
1
1
MUL AB
Multiply A and B
1
4
DIV AB
Divide A by B
1
8
DA A
Decimal adjust A
1
1
Logical Operations
ANL A, Rn
AND Register to A
1
1
ANL A, direct
AND direct byte to A
2
2
ANL A, @Ri
AND indirect RAM to A
1
2
ANL A, #data
AND immediate to A
2
2
ANL direct, A
AND A to direct byte
2
2
ANL direct, #data
AND immediate to direct byte
3
3
ORL A, Rn
OR Register to A
1
1
ORL A, direct
OR direct byte to A
2
2
ORL A, @Ri
OR indirect RAM to A
1
2
ORL A, #data
OR immediate to A
2
2
ORL direct, A
OR A to direct byte
2
2
ORL direct, #data
OR immediate to direct byte
3
3
XRL A, Rn
Exclusive-OR Register to A
1
1
108
Preliminary Rev 0.6
Table 15.1. CIP-51 Instruction Set Summary
Mnemonic
Description
Bytes
Clock
Cycles
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
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
Preliminary Rev 0.6
109
CIP-51 Microcontroller Core
C8051F85x/86x
CIP-51 Microcontroller Core
C8051F85x/86x
Table 15.1. CIP-51 Instruction Set Summary
Mnemonic
XCHD A, @Ri
Description
Exchange low nibble of indirect RAM with A
Bytes
Clock
Cycles
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
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 subroutine call
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
3
3/4
CJNE @Ri, #data, rel
Compare immediate to indirect and jump if not equal
3
4/5
DJNZ Rn, rel
Decrement Register and jump if not zero
2
2/3
DJNZ direct, rel
Decrement direct byte and jump if not zero
3
3/4
NOP
No operation
1
1
110
Preliminary Rev 0.6
Notes on Registers, Operands and Addressing Modes:
Rn—Register R0–R7 of the currently selected register bank.
@Ri—Data RAM location addressed indirectly through R0 or R1.
rel—8-bit, signed (twos complement) offset relative to the first byte of the following instruction. Used by SJMP
and all conditional jumps.
direct—8-bit internal data location’s address. This could be a direct-access Data RAM location (0x00–0x7F) or
an SFR (0x80–0xFF).
#data—8-bit constant
#data16—16-bit constant
bit—Direct-accessed bit in Data RAM or SFR
addr11—11-bit destination address used by ACALL and AJMP. The destination must be within the same 2 kB
page of program memory as the first byte of the following instruction.
addr16—16-bit destination address used by LCALL and LJMP. The destination may be anywhere within the
8 kB program memory space.
There is one unused opcode (0xA5) that performs the same function as NOP.
All mnemonics copyrighted © Intel Corporation 1980.
Preliminary Rev 0.6
111
CIP-51 Microcontroller Core
C8051F85x/86x
CIP-51 Microcontroller Core
C8051F85x/86x
15.4. CPU Core Registers
Register 15.1. DPL: Data Pointer Low
Bit
7
6
5
4
Name
DPL
Type
RW
Reset
0
0
0
0
3
2
1
0
0
0
0
0
SFR Address: 0x82
Table 15.2. DPL Register Bit Descriptions
Bit
Name
7:0
DPL
Function
Data Pointer Low.
The DPL register is the low byte of the 16-bit DPTR. DPTR is used to access indirectly
addressed flash memory or XRAM.
112
Preliminary Rev 0.6
Register 15.2. DPH: Data Pointer High
Bit
7
6
5
4
Name
DPH
Type
RW
Reset
0
0
0
0
3
2
1
0
0
0
0
0
SFR Address: 0x83
Table 15.3. DPH Register Bit Descriptions
Bit
Name
7:0
DPH
Function
Data Pointer High.
The DPH register is the high byte of the 16-bit DPTR. DPTR is used to access indirectly
addressed flash memory or XRAM.
Preliminary Rev 0.6
113
CIP-51 Microcontroller Core
C8051F85x/86x
CIP-51 Microcontroller Core
C8051F85x/86x
Register 15.3. SP: Stack Pointer
Bit
7
6
5
4
Name
SP
Type
RW
Reset
0
0
0
0
3
2
1
0
0
1
1
1
SFR Address: 0x81
Table 15.4. SP Register Bit Descriptions
Bit
Name
7:0
SP
Function
Stack Pointer.
The Stack Pointer holds the location of the top of the stack. The stack pointer is incremented before every PUSH operation. The SP register defaults to 0x07 after reset.
114
Preliminary Rev 0.6
Register 15.4. ACC: Accumulator
Bit
7
6
5
4
Name
ACC
Type
RW
Reset
0
0
0
0
3
2
1
0
0
0
0
0
SFR Address: 0xE0 (bit-addressable)
Table 15.5. ACC Register Bit Descriptions
Bit
Name
7:0
ACC
Function
Accumulator.
This register is the accumulator for arithmetic operations.
Preliminary Rev 0.6
115
CIP-51 Microcontroller Core
C8051F85x/86x
CIP-51 Microcontroller Core
C8051F85x/86x
Register 15.5. B: B Register
Bit
7
6
5
4
Name
B
Type
RW
Reset
0
0
0
0
3
2
1
0
0
0
0
0
SFR Address: 0xF0 (bit-addressable)
Table 15.6. B Register Bit Descriptions
Bit
Name
7:0
B
Function
B Register.
This register serves as a second accumulator for certain arithmetic operations.
116
Preliminary Rev 0.6
Register 15.6. PSW: Program Status Word
Bit
7
6
5
Name
CY
AC
F0
Type
RW
RW
RW
Reset
0
0
0
4
3
2
1
0
RS
OV
F1
PARITY
RW
RW
RW
R
0
0
0
0
0
SFR Address: 0xD0 (bit-addressable)
Table 15.7. PSW Register Bit Descriptions
Bit
Name
7
CY
Function
Carry Flag.
This bit is set when the last arithmetic operation resulted in a carry (addition) or a borrow
(subtraction). It is cleared to logic 0 by all other arithmetic operations.
6
AC
Auxiliary Carry Flag.
This bit is set when the last arithmetic operation resulted in a carry into (addition) or a
borrow from (subtraction) the high order nibble. It is cleared to logic 0 by all other arithmetic operations.
5
F0
User Flag 0.
This is a bit-addressable, general purpose flag for use under software control.
4:3
RS
Register Bank Select.
These bits select which register bank is used during register accesses.
00: Bank 0, Addresses 0x00-0x07
01: Bank 1, Addresses 0x08-0x0F
10: Bank 2, Addresses 0x10-0x17
11: Bank 3, Addresses 0x18-0x1F
2
OV
Overflow Flag.
This bit is set to 1 under the following circumstances:
1. An ADD, ADDC, or SUBB instruction causes a sign-change overflow.
2. A MUL instruction results in an overflow (result is greater than 255).
3. A DIV instruction causes a divide-by-zero condition.
The OV bit is cleared to 0 by the ADD, ADDC, SUBB, MUL, and DIV instructions in all
other cases.
1
F1
User Flag 1.
This is a bit-addressable, general purpose flag for use under software control.
0
PARITY
Parity Flag.
This bit is set to logic 1 if the sum of the eight bits in the accumulator is odd and cleared
if the sum is even.
Preliminary Rev 0.6
117
CIP-51 Microcontroller Core
C8051F85x/86x
Clock Sources and Selection (HFOSC0, LFOSC0, and EXTCLK)
C8051F85x/86x
16. Clock Sources and Selection (HFOSC0, LFOSC0, and EXTCLK)
The C8051F85x/86x devices can be clocked from the internal low power 24.5 MHz oscillator, the internal lowfrequency 80 kHz oscillator, or an external CMOS clock signal at the EXTCLK pin. An adjustable clock divider
allows the selected clock source to be post-scaled by powers of 2, up to a factor of 128. By default, the system
clock comes up as the 24.5 MHz oscillator divided by 8.
Clock Control
High Frequency
24.5 MHz
Oscillator
Low Frequency
80 kHz
Oscillator
Programmable
Divider:
1, 2, 4...128
SYSCLK
To core and
peripherals
External Clock
Input (EXTCLK)
Figure 16.1. Clocking Options
16.1. Programmable High-Frequency Oscillator
All C8051F85x/86x devices include a programmable internal high-frequency oscillator that defaults as the system
clock after a system reset. The oscillator is automatically enabled when it is requested. The internal oscillator
period can be adjusted via the OSCICL register. On C8051F85x/86x devices, OSCICL is factory calibrated to
obtain a 24.5 MHz base frequency.
16.2. Programmable Low-Frequency Oscillator
A programmable low-frequency internal oscillator is also included. The low-frequency oscillator is calibrated to a
nominal frequency of 80 kHz. A divider at the oscillator output is capable of dividing the output clock of the module
by 1, 2, 4, or 8, using the OSCLD bits in the OSCLCN register. Additionally, the OSCLF bits can be used to
coarsely adjust the oscillator’s output frequency.
16.2.1. Calibrating the Internal L-F Oscillator
Timer 3 includes a capture function that can be used to capture the oscillator frequency, when running from a
known time base. When Timer 3 is configured for L-F Oscillator Capture Mode, a rising edge of the low-frequency
oscillator’s output will cause a capture event on the corresponding timer. As a capture event occurs, the current
timer value (TMR3H:TMR3L) is copied into the timer reload registers (TMR3RLH:TMR3RLL). By recording the
difference between two successive timer capture values, the low-frequency oscillator’s period can be calculated.
The OSCLF bits can then be adjusted to produce the desired oscillator frequency.
16.3. External Clock
An external CMOS clock source is also supported by the C8051F85x/86x family. The EXTCLK pin on the device
serves as the external clock input when running in this mode. The EXTCLK input may also be used to clock some
of the digital peripherals (e.g., Timers, PCA, etc.) while SYSCLK runs from one of the internal oscillator sources.
When not selected as the SYSCLK source, the EXTCLK input is always re-synchronized to SYSCLK.
118
Preliminary Rev 0.6
16.4. Clock Selection
The CLKSEL register is used to select the clock source for the system. The CLKSL field selects which oscillator
source is used as the system clock, while CLKDIV controls the programmable divider. CLKSL must be set to 01b
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. In these cases, the external
oscillator source is synchronized to the SYSCLK source. The system clock may be switched on-the-fly between
any of the oscillator sources so long as the selected clock source is enabled and has settled, and CLKDIV may be
changed at any time.
The internal high-frequency and low-frequency oscillators require little start-up time and may be selected as the
system clock immediately following the register write which enables the oscillator. When selecting the EXTCLK pin
as a clock input source, the pin should be skipped in the crossbar and configured as a digital input. Firmware
should ensure that the external clock source is present or enable the missing clock detector before switching the
CLKSL field.
Preliminary Rev 0.6
119
Clock Sources and Selection (HFOSC0, LFOSC0, and EXTCLK)
C8051F85x/86x
Clock Sources and Selection (HFOSC0, LFOSC0, and EXTCLK)
C8051F85x/86x
16.5. High Frequency Oscillator Control Registers
Register 16.1. OSCICL: High Frequency Oscillator Calibration
Bit
7
6
5
4
Name
OSCICL
Type
RW
Reset
X
X
X
X
3
2
1
0
X
X
X
X
SFR Address: 0xC7
Table 16.1. OSCICL Register Bit Descriptions
Bit
Name
7:0
OSCICL
Function
Oscillator Calibration Bits.
These bits determine the internal oscillator period. When set to 00000000b, the oscillator
operates at its fastest setting. When set to 11111111b, the oscillator operates at its slowest setting. The reset value is factory calibrated to generate an internal oscillator frequency of 24.5 MHz.
120
Preliminary Rev 0.6
16.6. Low Frequency Oscillator Control Registers
Register 16.2. OSCLCN: Low Frequency Oscillator Control
Bit
7
6
5
4
Name
OSCLEN
OSCLRDY
OSCLF
OSCLD
Type
RW
R
RW
RW
Reset
0
0
X
3
X
X
2
X
1
0
0
0
SFR Address: 0xB1
Table 16.2. OSCLCN Register Bit Descriptions
Bit
Name
7
OSCLEN
Function
Internal L-F Oscillator Enable.
This bit enables the internal low-frequency oscillator. Note that the low-frequency oscillator is automatically enabled when the watchdog timer is active.
0: Internal L-F Oscillator Disabled.
1: Internal L-F Oscillator Enabled.
6
OSCLRDY
Internal L-F Oscillator Ready.
0: Internal L-F Oscillator frequency not stabilized.
1: Internal L-F Oscillator frequency stabilized.
5:2
OSCLF
Internal L-F Oscillator Frequency Control Bits.
Fine-tune control bits for the Internal L-F oscillator frequency. When set to 0000b, the L-F
oscillator operates at its fastest setting. When set to 1111b, the L-F oscillator operates at
its slowest setting. The OSCLF bits should only be changed by firmware when the L-F
oscillator is disabled (OSCLEN = 0).
1:0
OSCLD
Internal L-F Oscillator Divider Select.
00: Divide by 8 selected.
01: Divide by 4 selected.
10: Divide by 2 selected.
11: Divide by 1 selected.
Note: OSCLRDY is only set back to 0 in the event of a device reset or a change to the OSCLD bits.
Preliminary Rev 0.6
121
Clock Sources and Selection (HFOSC0, LFOSC0, and EXTCLK)
C8051F85x/86x
Clock Sources and Selection (HFOSC0, LFOSC0, and EXTCLK)
C8051F85x/86x
16.7. Clock Selection Control Registers
Register 16.3. CLKSEL: Clock Select
Bit
7
6
Name
Reserved
CLKDIV
Reserved
CLKSL
Type
R
RW
R
RW
Reset
0
0
5
4
1
3
1
2
0
0
1
0
0
0
SFR Address: 0xA9
Table 16.3. CLKSEL Register Bit Descriptions
Bit
Name
Function
7
Reserved
Must write reset value.
6:4
CLKDIV
Clock Source Divider.
This field controls the divider applied to the clock source selected by CLKSL. The output
of this divider is the system clock (SYSCLK).
000: SYSCLK is equal to selected clock source divided by 1.
001: SYSCLK is equal to selected clock source divided by 2.
010: SYSCLK is equal to selected clock source divided by 4.
011: SYSCLK is equal to selected clock source divided by 8.
100: SYSCLK is equal to selected clock source divided by 16.
101: SYSCLK is equal to selected clock source divided by 32.
110: SYSCLK is equal to selected clock source divided by 64.
111: SYSCLK is equal to selected clock source divided by 128.
3:2
Reserved
Must write reset value.
1:0
CLKSL
Clock Source Select.
Selects the system clock source.
00: Clock derived from the Internal High-Frequency Oscillator.
01: Clock derived from the External Oscillator circuit.
10: Clock derived from the Internal Low-Frequency Oscillator.
11: Reserved.
122
Preliminary Rev 0.6
17. Comparators (CMP0 and CMP1)
C8051F85x/86x devices include two on-chip programmable voltage comparators, CMP0 and CMP1. The two
comparators are functionally identical, but have different connectivity within the device. A functional block diagram
is shown in Figure 17.1.
CMPn
Positive Input
Selection
Programmable
Hysteresis
Port Pins (8)
Internal LDO
CPnA
(asynchronous)
CPn+
CPnSYSCLK
Port Pins (8)
GND
Negative Input
Selection
D
Q
CPn
(synchronous)
Q
Programmable
Response Time
Figure 17.1. Comparator Functional Block Diagram
17.1. System Connectivity
Comparator inputs are routed to port I/O pins or internal signals using the comparator mux registers. The
comparator’s synchronous and asynchronous outputs can optionally be routed to port I/O pins through the port I/O
crossbar. The output of either comparator may also be configured to generate a system interrupt. CMP0 may also
be used as a reset source, or as a trigger to kill a PCA output channel.
The CMP0 inputs are selected in the CPT0MX register, while CPT1MX selects the CMP1 inputs. The CMXP field
selects the comparator’s positive input (CPnP.x); the CMXN field selects the comparator’s negative input (CPnN.x).
Table 17.1 through Table 17.4 detail the comparator input multiplexer options on the C8051F85x/86x family. See
the port I/O crossbar sections for details on configuring comparator outputs via the digital crossbar. Comparator
inputs can be externally driven from –0.25 V to (VDD) + 0.25 V without damage or upset.
Important Note About Comparator Inputs: The port pins selected as comparator inputs should be configured as
analog inputs in their associated port configuration register, and configured to be skipped by the crossbar.
Preliminary Rev 0.6
123
Comparators (CMP0 and CMP1)
C8051F85x/86x
Comparators (CMP0 and CMP1)
C8051F85x/86x
Table 17.1. CMP0 Positive Input Multiplexer Channels
CMXP Setting in
Register CPT0MX
Signal Name
QSOP24 Pin Name
QFN20 Pin Name
SOIC16 Pin Name
0000
CP0P.0
P0.0
P0.0
P0.0
0001
CP0P.1
P0.1
P0.1
P0.1
0010
CP0P.2
P0.2
P0.2
P0.2
0011
CP0P.3
P0.3
P0.3
P0.3
0100
CP0P.4
P0.4
P0.4
P0.4
0101
CP0P.5
P0.5
P0.5
P0.5
0110
CP0P.6
P0.6
P0.6
Reserved
0111
CP0P.7
P0.7
P0.7
Reserved
1000
LDO
Internal 1.8 V LDO Output
1001-1111
None
No connection
Table 17.2. CMP0 Negative Input Multiplexer Channels
CMXN Setting in
Register CPT0MX
Signal Name
QSOP24 Pin Name
QFN20 Pin Name
SOIC16 Pin Name
0000
CP0N.0
P0.0
P0.0
P0.0
0001
CP0N.1
P0.1
P0.1
P0.1
0010
CP0N.2
P0.2
P0.2
P0.2
0011
CP0N.3
P0.3
P0.3
P0.3
0100
CP0N.4
P0.4
P0.4
P0.4
0101
CP0N.5
P0.5
P0.5
P0.5
0110
CP0N.6
P0.6
P0.6
Reserved
0111
CP0N.7
P0.7
P0.7
Reserved
1000
GND
GND
1001-1111
None
No connection
124
Preliminary Rev 0.6
Table 17.3. CMP1 Positive Input Multiplexer Channels
CMXP Setting in
Register CPT1MX
Signal Name
QSOP24 Pin Name
QFN20 Pin Name
SOIC16 Pin Name
0000
CP1P.0
P1.0
P1.0
P0.6
0001
CP1P.1
P1.1
P1.1
P0.7
0010
CP1P.2
P1.2
P1.2
P1.0
0011
CP1P.3
P1.3
P1.3
P1.1
0100
CP1P.4
P1.4
P1.4
P1.2
0101
CP1P.5
P1.5
P1.5
P1.3
0110
CP1P.6
P1.6
P1.6
Reserved
0111
CP1P.7
P1.7
Reserved
Reserved
1000
LDO
Internal 1.8 V LDO Output
1001-1111
None
No connection
Table 17.4. CMP1 Negative Input Multiplexer Channels
CMXN Setting in
Register CPT1MX
Signal Name
QSOP24 Pin Name
QFN20 Pin Name
SOIC16 Pin Name
0000
CP1N.0
P1.0
P1.0
P0.6
0001
CP1N.1
P1.1
P1.1
P0.7
0010
CP1N.2
P1.2
P1.2
P1.0
0011
CP1N.3
P1.3
P1.3
P1.1
0100
CP1N.4
P1.4
P1.4
P1.2
0101
CP1N.5
P1.5
P1.5
P1.3
0110
CP1N.6
P1.6
P1.6
Reserved
0111
CP1N.7
P1.7
Reserved
Reserved
1000
GND
GND
1001-1111
None
No connection
Preliminary Rev 0.6
125
Comparators (CMP0 and CMP1)
C8051F85x/86x
Comparators (CMP0 and CMP1)
C8051F85x/86x
17.2. Functional Description
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 (CPn), or an asynchronous “raw”
output (CPnA). The asynchronous CPnA 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 disabled, the comparator output (if assigned to a port I/O pin via the crossbar) defaults to the logic low state,
and the power supply to the comparator is turned off.
The comparator response time may be configured in software via the CPTnMD register. Selecting a longer
response time reduces the comparator supply current.
Positive programmable
hysteresis (CPHYP)
CPnCPn+
Negative programmable
hysteresis (CPHYN)
CP0 (out)
Figure 17.2. Comparator Hysteresis Plot
The comparator hysteresis is software-programmable via its Comparator Control register CPTnCN. The user can
program both the amount of hysteresis voltage (referred to the input voltage) and the positive and negative-going
symmetry of this hysteresis around the threshold voltage.
The comparator hysteresis is programmable using the CPHYN and CPHYP fields in the Comparator Control
Register CPTnCN. The amount of negative hysteresis voltage is determined by the settings of the CPHYN bits. As
shown in Figure 17.2, settings of 20, 10, or 5 mV (nominal) of negative hysteresis can be programmed, or negative
hysteresis can be disabled. In a similar way, the amount of positive hysteresis is determined by the setting the
CPHYP bits.
Comparator interrupts can be generated on both rising-edge and falling-edge output transitions. The CPFIF flag is
set to logic 1 upon a comparator falling-edge occurrence, and the CPRIF flag is set to logic 1 upon the comparator
rising-edge occurrence. Once set, these bits remain set until cleared by software. The comparator rising-edge
interrupt mask is enabled by setting CPRIE to a logic 1. The comparator falling-edge interrupt mask is enabled by
setting CPFIE to a logic 1.
The output state of the comparator can be obtained at any time by reading the CPOUT bit. The comparator is
enabled by setting the CPEN bit to logic 1, and is disabled by clearing this bit to logic 0.
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 risingedge 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, before enabling comparator interrupts.
126
Preliminary Rev 0.6
17.3. Comparator Control Registers
Register 17.1. CPT0CN: Comparator 0 Control
Bit
7
6
5
4
3
2
Name
CPEN
CPOUT
CPRIF
CPFIF
CPHYP
CPHYN
Type
RW
R
RW
RW
RW
RW
Reset
0
0
0
0
0
0
1
0
0
0
SFR Address: 0x9B
Table 17.5. CPT0CN Register Bit Descriptions
Bit
Name
7
CPEN
Function
Comparator 0 Enable Bit.
0: Comparator Disabled.
1: Comparator Enabled.
6
CPOUT
Comparator 0 Output State Flag.
0: Voltage on CP0P < CP0N.
1: Voltage on CP0P > CP0N.
5
CPRIF
Comparator 0 Rising-Edge Flag. Must be cleared by software.
0: No Comparator Rising Edge has occurred since this flag was last cleared.
1: Comparator Rising Edge has occurred.
4
CPFIF
Comparator 0 Falling-Edge Flag. Must be cleared by software.
0: No Comparator Falling-Edge has occurred since this flag was last cleared.
1: Comparator Falling-Edge has occurred.
3:2
CPHYP
Comparator 0 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
CPHYN
Comparator 0 Negative Hysteresis Control Bits.
00: Negative Hysteresis Disabled.
01: Negative Hysteresis = 5 mV.
10: Negative Hysteresis = 10 mV.
11: Negative Hysteresis = 20 mV.
Preliminary Rev 0.6
127
Comparators (CMP0 and CMP1)
C8051F85x/86x
Comparators (CMP0 and CMP1)
C8051F85x/86x
Register 17.2. CPT0MD: Comparator 0 Mode
Bit
7
6
5
4
3
2
Name
CPLOUT
Reserved
CPRIE
CPFIE
Reserved
CPMD
Type
RW
R
RW
RW
R
RW
Reset
0
0
0
0
0
0
1
0
1
0
SFR Address: 0x9D
Table 17.6. CPT0MD Register Bit Descriptions
Bit
Name
7
CPLOUT
Function
Comparator 0 Latched Output Flag.
This bit represents the comparator output value at the most recent PCA counter overflow.
0: Comparator output was logic low at last PCA overflow.
1: Comparator output was logic high at last PCA overflow.
6
Reserved
5
CPRIE
Must write reset value.
Comparator 0 Rising-Edge Interrupt Enable.
0: Comparator Rising-edge interrupt disabled.
1: Comparator Rising-edge interrupt enabled.
4
CPFIE
Comparator 0 Falling-Edge Interrupt Enable.
0: Comparator Falling-edge interrupt disabled.
1: Comparator Falling-edge interrupt enabled.
3:2
Reserved
1:0
CPMD
Must write reset value.
Comparator 0 Mode Select.
These bits affect the response time and power consumption of the comparator.
00: Mode 0 (Fastest Response Time, Highest Power Consumption)
01: Mode 1
10: Mode 2
11: Mode 3 (Slowest Response Time, Lowest Power Consumption)
128
Preliminary Rev 0.6
Register 17.3. CPT0MX: Comparator 0 Multiplexer Selection
Bit
7
6
5
4
3
2
Name
CMXN
CMXP
Type
RW
RW
Reset
1
1
1
1
1
1
1
0
1
1
SFR Address: 0x9F
Table 17.7. CPT0MX Register Bit Descriptions
Bit
Name
7:4
CMXN
Function
Comparator 0 Negative Input MUX Selection.
0000: External pin CP0N.0
0001: External pin CP0N.1
0010: External pin CP0N.2
0011: External pin CP0N.3
0100: External pin CP0N.4
0101: External pin CP0N.5
0110: External pin CP0N.6
0111: External pin CP0N.7
1000: GND
1001-1111: Reserved.
3:0
CMXP
Comparator 0 Positive Input MUX Selection.
0000: External pin CP0P.0
0001: External pin CP0P.1
0010: External pin CP0P.2
0011: External pin CP0P.3
0100: External pin CP0P.4
0101: External pin CP0P.5
0110: External pin CP0P.6
0111: External pin CP0P.7
1000: Internal LDO output
1001-1111: Reserved.
Preliminary Rev 0.6
129
Comparators (CMP0 and CMP1)
C8051F85x/86x
Comparators (CMP0 and CMP1)
C8051F85x/86x
Register 17.4. CPT1CN: Comparator 1 Control
Bit
7
6
5
4
3
2
Name
CPEN
CPOUT
CPRIF
CPFIF
CPHYP
CPHYN
Type
RW
R
RW
RW
RW
RW
Reset
0
0
0
0
0
0
1
0
0
SFR Address: 0xBF
Table 17.8. CPT1CN Register Bit Descriptions
Bit
Name
7
CPEN
Function
Comparator 1 Enable Bit.
0: Comparator Disabled.
1: Comparator Enabled.
6
CPOUT
Comparator 1 Output State Flag.
0: Voltage on CP1P < CP1N.
1: Voltage on CP1P > CP1N.
5
CPRIF
Comparator 1 Rising-Edge Flag. Must be cleared by software.
0: No Comparator Rising Edge has occurred since this flag was last cleared.
1: Comparator Rising Edge has occurred.
4
CPFIF
Comparator 1 Falling-Edge Flag. Must be cleared by software.
0: No Comparator Falling-Edge has occurred since this flag was last cleared.
1: Comparator Falling-Edge has occurred.
3:2
CPHYP
Comparator 1 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
CPHYN
Comparator 1 Negative Hysteresis Control Bits.
00: Negative Hysteresis Disabled.
01: Negative Hysteresis = 5 mV.
10: Negative Hysteresis = 10 mV.
11: Negative Hysteresis = 20 mV.
130
Preliminary Rev 0.6
0
Register 17.5. CPT1MD: Comparator 1 Mode
Bit
7
6
5
4
3
2
Name
CPLOUT
Reserved
CPRIE
CPFIE
Reserved
CPMD
Type
RW
R
RW
RW
R
RW
Reset
0
0
0
0
0
0
1
0
1
0
SFR Address: 0xAB
Table 17.9. CPT1MD Register Bit Descriptions
Bit
Name
7
CPLOUT
Function
Comparator 1 Latched Output Flag.
This bit represents the comparator output value at the most recent PCA counter overflow.
0: Comparator output was logic low at last PCA overflow.
1: Comparator output was logic high at last PCA overflow.
6
Reserved
5
CPRIE
Must write reset value.
Comparator 1 Rising-Edge Interrupt Enable.
0: Comparator Rising-edge interrupt disabled.
1: Comparator Rising-edge interrupt enabled.
4
CPFIE
Comparator 1 Falling-Edge Interrupt Enable.
0: Comparator Falling-edge interrupt disabled.
1: Comparator Falling-edge interrupt enabled.
3:2
Reserved
1:0
CPMD
Must write reset value.
Comparator 1 Mode Select.
These bits affect the response time and power consumption of the comparator.
00: Mode 0 (Fastest Response Time, Highest Power Consumption)
01: Mode 1
10: Mode 2
11: Mode 3 (Slowest Response Time, Lowest Power Consumption)
Preliminary Rev 0.6
131
Comparators (CMP0 and CMP1)
C8051F85x/86x
Comparators (CMP0 and CMP1)
C8051F85x/86x
Register 17.6. CPT1MX: Comparator 1 Multiplexer Selection
Bit
7
6
5
4
3
2
Name
CMXN
CMXP
Type
RW
RW
Reset
1
1
1
1
1
1
SFR Address: 0xAA
Table 17.10. CPT1MX Register Bit Descriptions
Bit
Name
7:4
CMXN
Function
Comparator 1 Negative Input MUX Selection.
0000: External pin CP1N.0
0001: External pin CP1N.1
0010: External pin CP1N.2
0011: External pin CP1N.3
0100: External pin CP1N.4
0101: External pin CP1N.5
0110: External pin CP1N.6
0111: External pin CP1N.7
1000: GND
1001-1111: Reserved.
3:0
CMXP
Comparator 1 Positive Input MUX Selection.
0000: External pin CP1P.0
0001: External pin CP1P.1
0010: External pin CP1P.2
0011: External pin CP1P.3
0100: External pin CP1P.4
0101: External pin CP1P.5
0110: External pin CP1P.6
0111: External pin CP1P.7
1000: Internal LDO output
1001-1111: Reserved.
132
Preliminary Rev 0.6
1
0
1
1
18. Cyclic Redundancy Check Unit (CRC0)
C8051F85x/86x devices include a cyclic redundancy check unit (CRC0) that can perform a CRC using a 16-bit
polynomial. CRC0 accepts a stream of 8-bit data written to the CRC0IN register. CRC0 posts the 16-bit result to an
internal register. The internal result register may be accessed indirectly using the CRCPNT bits and CRC0DAT
register, as shown in Figure 18.1. CRC0 also has a bit reverse register for quick data manipulation.
CRC0
CRC0IN
Flash
Memory
Automatic
flash read
control
8
8
Seed
(0x0000 or
0xFFFF)
CRC0FLIP
8
byte-level bit
reversal
Hardware CRC
Calculation
Unit
8
8
8
CRC0DAT
Figure 18.1. CRC0 Block Diagram
18.1. CRC Algorithm
The CRC unit generates a CRC result equivalent to the following algorithm:
1. XOR the input with the most-significant bits of the current CRC result. If this is the first iteration of the CRC
unit, the current CRC result will be the set initial value 
(0x0000 or 0xFFFF).
2a. If the MSB of the CRC result is set, shift the CRC result and XOR the result with the selected polynomial.
2b. If the MSB of the CRC result is not set, shift the CRC result.
Repeat Steps 2a/2b for the number of input bits (8). The algorithm is also described in the following example.
Preliminary Rev 0.6
133
Cyclic Redundancy Check Unit (CRC0)
C8051F85x/86x
Cyclic Redundancy Check Unit (CRC0)
C8051F85x/86x
The 16-bit CRC algorithm can be described by the following code:
unsigned short UpdateCRC (unsigned short CRC_acc, unsigned char CRC_input)
{
unsigned char i;
// loop counter
#define POLY 0x1021
// Create the CRC "dividend" for polynomial arithmetic (binary arithmetic
// with no carries)
CRC_acc = CRC_acc ^ (CRC_input << 8);
// "Divide" the poly into the dividend using CRC XOR subtraction
// CRC_acc holds the "remainder" of each divide
//
// Only complete this division for 8 bits since input is 1 byte
for (i = 0; i < 8; i++)
{
// Check if the MSB is set (if MSB is 1, then the POLY can "divide"
// into the "dividend")
if ((CRC_acc & 0x8000) == 0x8000)
{
// if so, shift the CRC value, and XOR "subtract" the poly
CRC_acc = CRC_acc << 1;
CRC_acc ^= POLY;
}
else
{
// if not, just shift the CRC value
CRC_acc = CRC_acc << 1;
}
}
}
// Return the final remainder (CRC value)
return CRC_acc;
Table 18.1 lists several input values and the associated outputs using the 16-bit CRC algorithm:
Table 18.1. Example 16-bit CRC Outputs
134
Input
Output
0x63
0xBD35
0x8C
0xB1F4
0x7D
0x4ECA
0xAA, 0xBB, 0xCC
0x6CF6
0x00, 0x00, 0xAA, 0xBB, 0xCC
0xB166
Preliminary Rev 0.6
18.2. Preparing for a CRC Calculation
To prepare CRC0 for a CRC calculation, software should set the initial value of the result. The polynomial used for
the CRC computation is 0x1021. The CRC0 result may be initialized to one of two values: 0x0000 or 0xFFFF. The
following steps can be used to initialize CRC0.
1. Select the initial result value (Set CRCVAL to 0 for 0x0000 or 1 for 0xFFFF).
2. Set the result to its initial value (Write 1 to CRCINIT).
18.3. Performing a CRC Calculation
Once CRC0 is initialized, the input data stream is sequentially written to CRC0IN, one byte at a time. The CRC0
result is automatically updated after each byte is written. The CRC engine may also be configured to automatically
perform a CRC on one or more 256 byte blocks read from flash. The following steps can be used to automatically
perform a CRC on flash memory.
1. Prepare CRC0 for a CRC calculation as shown above.
2. Write the index of the starting page to CRC0AUTO.
3. Set the AUTOEN bit to 1 in CRC0AUTO.
4. Write the number of 256 byte blocks to perform in the CRC calculation to CRCCNT.
5. Write any value to CRC0CN (or OR its contents with 0x00) to initiate the CRC calculation. The CPU will not
execute code any additional code until the CRC operation completes. See the note in the CRC0CN
register definition for more information on how to properly initiate a CRC calculation.
6. Clear the AUTOEN bit in CRC0AUTO.
7. Read the CRC result.
18.4. Accessing the CRC0 Result
The internal CRC0 result is 16 bits. The CRCPNT bits select the byte that is targeted by read and write operations
on CRC0DAT and increment after each read or write. The calculation result will remain in the internal CR0 result
register until it is set, overwritten, or additional data is written to CRC0IN.
18.5. CRC0 Bit Reverse Feature
CRC0 includes hardware to reverse the bit order of each bit in a byte as shown in Figure 18.2. Each byte of data
written to CRC0FLIP is read back bit reversed. For example, if 0xC0 is written to CRC0FLIP, the data read back is
0x03. Bit reversal is a useful mathematical function used in algorithms such as the FFT.
CRC0FLIP
(write)
CRC0FLIP
(read)
Figure 18.2. Bit Reversal
Preliminary Rev 0.6
135
Cyclic Redundancy Check Unit (CRC0)
C8051F85x/86x
Cyclic Redundancy Check Unit (CRC0)
C8051F85x/86x
18.6. CRC Control Registers
Register 18.1. CRC0CN: CRC0 Control
Bit
7
6
5
4
3
2
1
0
Name
Reserved
CRCINIT
CRCVAL
Reserved
CRCPNT
Type
R
RW
RW
R
RW
0
0
0
0
Reset
0
0
0
1
SFR Address: 0xCE
Table 18.2. CRC0CN Register Bit Descriptions
Bit
Name
Function
7:4
Reserved
Must write reset value.
3
CRCINIT
CRC Result Initialization Bit.
Writing a 1 to this bit initializes the entire CRC result based on CRCVAL.
2
CRCVAL
CRC Set Value Initialization Bit.
This bit selects the set value of the CRC result.
0: CRC result is set to 0x0000 on write of 1 to CRCINIT.
1: CRC result is set to 0xFFFF on write of 1 to CRCINIT.
1
Reserved
Must write reset value.
0
CRCPNT
CRC Result Pointer.
Specifies the byte of the CRC result to be read/written on the next access to CRC0DAT.
This bit will automatically toggle upon each read or write.
0: CRC0DAT accesses bits 7-0 of the 16-bit CRC result.
1: CRC0DAT accesses bits 15-8 of the 16-bit CRC result.
Note: Upon initiation of an automatic CRC calculation, the three cycles following a write to CRC0CN that initiate a CRC
operation must only contain instructions which execute in the same number of cycles as the number of bytes in the
instruction. An example of such an instruction is a 3-byte MOV that targets the CRC0FLIP register. When programming
in C, the dummy value written to CRC0FLIP should be a non-zero value to prevent the compiler from generating a 2byte MOV instruction.
136
Preliminary Rev 0.6
Register 18.2. CRC0IN: CRC0 Data Input
Bit
7
6
5
4
Name
CRC0IN
Type
RW
Reset
0
0
0
0
3
2
1
0
0
0
0
0
SFR Address: 0xDD
Table 18.3. CRC0IN Register Bit Descriptions
Bit
Name
7:0
CRC0IN
Function
CRC Data Input.
Each write to CRCIN results in the written data being computed into the existing CRC
result according to the CRC algorithm.
Preliminary Rev 0.6
137
Cyclic Redundancy Check Unit (CRC0)
C8051F85x/86x
Cyclic Redundancy Check Unit (CRC0)
C8051F85x/86x
Register 18.3. CRC0DAT: CRC0 Data Output
Bit
7
6
5
4
Name
CRC0DAT
Type
RW
Reset
0
0
0
0
3
2
1
0
0
0
0
0
SFR Address: 0xDE
Table 18.4. CRC0DAT Register Bit Descriptions
Bit
Name
7:0
CRC0DAT
Function
CRC Data Output.
Each read or write performed on CRC0DAT targets the CRC result bits pointed to by the
CRC0 Result Pointer (CRC0PNT bits in CRC0CN).
Note: CRC0DAT may not be valid for one cycle after setting the CRC0INIT bit in the CRC0CN register to 1. Any time
CRC0INIT is written to 1 by firmware, at least one instruction should be performed before reading CRC0DAT.
138
Preliminary Rev 0.6
Register 18.4. CRC0AUTO: CRC0 Automatic Control
Bit
7
6
5
4
Name
AUTOEN
Reserved
CRCST
Type
RW
R
RW
Reset
0
0
0
3
0
0
2
1
0
0
0
0
SFR Address: 0xD2
Table 18.5. CRC0AUTO Register Bit Descriptions
Bit
Name
7
AUTOEN
Function
Automatic CRC Calculation Enable.
When AUTOEN is set to 1, any write to CRC0CN will initiate an automatic CRC starting
at flash sector CRCST and continuing for CRCCNT sectors.
6
Reserved
5:0
CRCST
Must write reset value.
Automatic CRC Calculation Starting Block.
These bits specify the flash block to start the automatic CRC calculation. The starting
address of the first flash block included in the automatic CRC calculation is CRCST x
block_size, where block_size is 256 bytes.
Preliminary Rev 0.6
139
Cyclic Redundancy Check Unit (CRC0)
C8051F85x/86x
Cyclic Redundancy Check Unit (CRC0)
C8051F85x/86x
Register 18.5. CRC0CNT: CRC0 Automatic Flash Sector Count
Bit
7
6
Name
CRCDN
Reserved
CRCCNT
Type
R
R
RW
Reset
1
0
5
4
0
3
0
0
2
0
1
0
0
0
SFR Address: 0xD3
Table 18.6. CRC0CNT Register Bit Descriptions
Bit
Name
7
CRCDN
Function
Automatic CRC Calculation Complete.
Set to 0 when a CRC calculation is in progress. Code execution is stopped during a CRC
calculation; therefore, reads from firmware will always return 1.
6:5
Reserved
Must write reset value.
4:0
CRCCNT
Automatic CRC Calculation Block Count.
These bits specify the number of flash blocks to include in an automatic CRC calculation.
The last address of the last flash block included in the automatic CRC calculation is
(CRCST+CRCCNT) x Block Size - 1. The block size is 256 bytes.
140
Preliminary Rev 0.6
Register 18.6. CRC0FLIP: CRC0 Bit Flip
Bit
7
6
5
4
Name
CRC0FLIP
Type
RW
Reset
0
0
0
0
3
2
1
0
0
0
0
0
SFR Address: 0xCF
Table 18.7. CRC0FLIP Register Bit Descriptions
Bit
Name
7:0
CRC0FLIP
Function
CRC0 Bit Flip.
Any byte written to CRC0FLIP is read back in a bit-reversed order, i.e., the written LSB
becomes the MSB. For example:
If 0xC0 is written to CRC0FLIP, the data read back will be 0x03.
If 0x05 is written to CRC0FLIP, the data read back will be 0xA0.
Preliminary Rev 0.6
141
Cyclic Redundancy Check Unit (CRC0)
C8051F85x/86x
External Interrupts (INT0 and INT1)
C8051F85x/86x
19. External Interrupts (INT0 and INT1)
The C8051F85x/86x device family includes two external digital interrupt sources (INT0 and INT1), with dedicated
interrupt sources (up to 16 additional I/O interrupts are available through the port match function). As is the case on
a standard 8051 architecture, certain controls for these two interrupt sources are available in the Timer0/1
registers. Extensions to these controls which provide additional functionality on C8051F85x/86x devices are
available in the IT01CF register. INT0 and INT1 are configurable as active high or low, edge or level sensitive. The
IN0PL and IN1PL bits in the IT01CF register select active high or active low; the IT0 and IT1 bits in TCON select
level or edge sensitive. The table below lists the possible configurations.
IT1
IN1PL
Active low, edge sensitive
1
0
Active low, edge sensitive
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
IT0
IN0PL
1
0
1
INT0 Interrupt
INT1 Interrupt
INT0 and INT1 are assigned to port pins as defined in the IT01CF register. Note that INT0 and INT1 Port pin
assignments are independent of any crossbar assignments. INT0 and INT1 will monitor their assigned port pins
without disturbing the peripheral that was assigned the port pin via the crossbar. To assign a port pin only to INT0
and/or INT1, configure the crossbar to skip the selected pin(s).
IE0 and IE1 in the TCON register serve as the interrupt-pending flags for the INT0 and INT1 external interrupts,
respectively. If an INT0 or INT1 external interrupt is configured as edge-sensitive, the corresponding interruptpending flag is automatically cleared by the hardware when the CPU vectors to the ISR. When configured as level
sensitive, the interrupt-pending flag remains logic 1 while the input is active as defined by the corresponding
polarity bit (IN0PL or IN1PL); the flag remains logic 0 while the input is inactive. The external interrupt source must
hold the input active until the interrupt request is recognized. It must then deactivate the interrupt request before
execution of the ISR completes or another interrupt request will be generated.
142
Preliminary Rev 0.6
19.1. External Interrupt Control Registers
Register 19.1. IT01CF: INT0/INT1 Configuration
Bit
7
6
5
Name
IN1PL
IN1SL
IN0PL
IN0SL
Type
RW
RW
RW
RW
Reset
0
0
4
0
3
0
0
2
0
1
0
0
1
SFR Address: 0xE4
Table 19.1. IT01CF Register Bit Descriptions
Bit
Name
7
IN1PL
Function
INT1 Polarity.
0: INT1 input is active low.
1: INT1 input is active high.
6:4
IN1SL
INT1 Port Pin Selection Bits.
These bits select which Port pin is assigned to INT1. This pin assignment is independent
of the Crossbar; INT1 will monitor the assigned Port pin without disturbing the peripheral
that has been assigned the Port pin via the Crossbar. The 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
3
IN0PL
INT0 Polarity.
0: INT0 input is active low.
1: INT0 input is active high.
2:0
IN0SL
INT0 Port Pin Selection Bits.
These bits select which Port pin is assigned to INT0. This pin assignment is independent
of the Crossbar; INT0 will monitor the assigned Port pin without disturbing the peripheral
that has been assigned the Port pin via the Crossbar. The 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
Preliminary Rev 0.6
143
External Interrupts (INT0 and INT1)
C8051F85x/86x
External Interrupts (INT0 and INT1)
C8051F85x/86x
144
Preliminary Rev 0.6
Programmable Counter Array (PCA0)
C8051F85x/86x
20. Programmable Counter Array (PCA0)
The Programmable Counter Array (PCA0) provides three channels of enhanced timer and PWM functionality while
requiring less CPU intervention than standard counter/timers. The PCA consists of a dedicated 16-bit counter/timer
and three 16-bit capture/compare modules. The counter/timer is driven by a programmable timebase that can
select between seven sources: system clock, system clock divided by four, system clock divided by twelve, the
external oscillator clock source divided by 8, low frequency oscillator divided by 8, Timer 0 overflows, or an external
clock signal on the ECI input pin. Each capture/compare module may be configured to operate independently in
one of six modes: Edge-Triggered Capture, Software Timer, High-Speed Output, Frequency Output, 8 to 11-Bit
PWM, or 16-Bit PWM. Additionally, all PWM modes support both center and edge-aligned operation. The external
oscillator and LFO oscillator clock options allow the PCA to be clocked by an external oscillator or the LFO while
the internal oscillator drives the system clock. 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 I/O signals have programmable polarity
and Comparator 0 can optionally be used to perform a cycle-by-cycle kill operation on the PCA outputs. A PCA
block diagram is shown in Figure 20.1
PCA0
SYSCLK
SYSCLK / 4
SYSCLK / 12
Timer 0 Overflow
PCA Counter
EXTCLK / 8
Sync
L-F Oscillator / 8
Sync
ECI
Sync
Control /
Configuration
Interrupt
Logic
SYSCLK
Channel 2
Mode
Control1
Channel
Capture
Mode
/ Compare
Control
Channel 0
Output
Drive
Logic
Capture
Mode
/ Compare
Control
Capture / Compare
Comparator 0 Output
Polarity Select
Comparator
Clear Enable
Figure 20.1. PCA0 Block Diagram
146
Preliminary Rev 0.6
CEX2
CEX1
CEX0
20.1. PCA Counter/Timer
The 16-bit PCA counter/timer consists of two 8-bit SFRs: PCA0L and PCA0H. PCA0H is the high byte of the 16-bit
counter/timer and PCA0L is the low byte. Reading PCA0L automatically latches the value of PCA0H into a
“snapshot” register; the following PCA0H read accesses this “snapshot” register. Reading the PCA0L Register
first guarantees an accurate reading of the entire 16-bit PCA0 counter. Reading PCA0H or PCA0L does not
disturb the counter operation. The CPS2–CPS0 bits in the PCA0MD register select the timebase for the counter/
timer as shown in Table 20.1.
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 software. Clearing the CIDL bit in the
PCA0MD register allows the PCA to continue normal operation while the CPU is in Idle mode.
Table 20.1. PCA Timebase Input Options
CPS2
CPS1
CPS0
Timebase
0
0
0
System clock divided by 12
0
0
1
System clock divided by 4
0
1
0
Timer 0 overflow
0
1
1
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
0
Low frequency oscillator divided by 8*
1
1
1
Reserved
Note: Synchronized with the system clock.
20.2. PCA0 Interrupt Sources
The PCA0 module shares one interrupt vector among all of its modules. There are are several event flags that can
be used to generate a PCA0 interrupt. They are: the main PCA counter overflow flag (CF), which is set upon a 16bit overflow of the PCA0 counter, an intermediate overflow flag (COVF), which can be set on an overflow from the
8th - 11th bit of the PCA0 counter, and the individual flags for each PCA channel (CCFn), which are set according
to the operation mode of that module. These event flags are always set when the trigger condition occurs. Each of
these flags can be individually selected to generate a PCA0 interrupt, using the corresponding interrupt enable flag
(ECF for CF, ECOV for COVF, and ECCFn for each CCFn). PCA0 interrupts must be globally enabled before any
individual interrupt sources are recognized by the processor. PCA0 interrupts are globally enabled by setting the
EA bit and the EPCA0 bit to logic 1.
Preliminary Rev 0.6
147
Programmable Counter Array (PCA0)
C8051F85x/86x
Programmable Counter Array (PCA0)
C8051F85x/86x
20.3. Capture/Compare Modules
Each module can be configured to operate independently in one of six operation modes: edge-triggered capture,
software timer, high-speed output, frequency output, 8 to 11-bit pulse width modulator, or 16-bit pulse width
modulator. Table 20.2 summarizes the bit settings in the PCA0CPMn and PCA0PWM registers used to select the
PCA capture/compare module’s operating mode. Note that all modules set to use 8, 9, 10 or 11-bit PWM mode
must use the same cycle length (8–11 bits). Setting the ECCFn bit in a PCA0CPMn register enables the module's
CCFn interrupt.
Table 20.2. PCA0CPM and PCA0PWM Bit Settings for PCA Capture/Compare Modules
Operational Mode
PCA0CPMn
PCA0PWM
Bit Number 7 6 5 4 3 2 1 0 7 6 5 4–3
2–0
Capture triggered by positive edge on CEXn
X X 1 0 0 0 0 A 0 X B XX
XXX
Capture triggered by negative edge on CEXn
X X 0 1 0 0 0 A 0 X B XX
XXX
Capture triggered by any transition on CEXn
X X 1 1 0 0 0 A 0 X B XX
XXX
Software Timer
X C 0 0 1 0 0 A 0 X B XX
XXX
High Speed Output
X C 0 0 1 1 0 A 0 X B XX
XXX
Frequency Output
X C 0 0 0 1 1 A 0 X B XX
XXX
8-Bit Pulse Width Modulator (Note 7)
0 C 0 0 E 0 1 A 0 X B XX
000
9-Bit Pulse Width Modulator (Note 7)
0 C 0 0 E 0 1 A D X B XX
001
10-Bit Pulse Width Modulator (Note 7)
0 C 0 0 E 0 1 A D X B XX
010
11-Bit Pulse Width Modulator (Note 7)
0 C 0 0 E 0 1 A D X B XX
011
16-Bit Pulse Width Modulator
1 C 0 0 E 0 1 A 0 X B XX
XXX
Notes:
1. X = Don’t Care (no functional difference for individual module if 1 or 0).
2. A = Enable interrupts for this module (PCA interrupt triggered on CCFn set to 1).
3. B = Enable 8th - 11th bit overflow interrupt (Depends on setting of CLSEL).
4. C = When set to 0, the digital comparator is off. For high speed and frequency output modes, the associated pin will not
toggle. In any of the PWM modes, this generates a 0% duty cycle (output = 0).
5. D = Selects whether the Capture/Compare register (0) or the Auto-Reload register (1) for the associated channel is
accessed via addresses PCA0CPHn and PCA0CPLn.
6. E = When set, a match event will cause the CCFn flag for the associated channel to be set.
7. All modules set to 8, 9, 10 or 11-bit PWM mode use the same cycle length setting.
20.3.1. Output Polarity
The output polarity of each PCA channel is individually selectable using the PCA0POL register. By default, all
output channels are configured to drive the PCA output signals (CEXn) with their internal polarity. When the
CEXnPOL bit for a specific channel is set to 1, that channel’s output signal will be inverted at the pin. All other
properties of the channel are unaffected, and the inversion does not apply to PCA input signals. Note that changes
in the PCA0POL register take effect immediately at the associated output pin.
148
Preliminary Rev 0.6
20.3.2. 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-tohigh 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 directly to
determine whether a rising-edge or falling-edge caused the capture.
CCFn (Interrupt Flag)
CAPPn
PCA0CPLn
PCA0CPHn
Capture
CEXn
CAPNn
PCA Clock
PCA0L
PCA0H
Figure 20.2. PCA Capture Mode Diagram
Note: The CEXn input signal must remain high or low for at least 2 system clock cycles to be recognized by the hardware.
Preliminary Rev 0.6
149
Programmable Counter Array (PCA0)
C8051F85x/86x
Programmable Counter Array (PCA0)
C8051F85x/86x
20.3.3. Software Timer (Compare) Mode
In Software Timer mode, the PCA counter/timer value is compared to the module's 16-bit capture/compare register
(PCA0CPHn and PCA0CPLn). When a match occurs, the Capture/Compare Flag (CCFn) in PCA0CN is set to
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. Setting the ECOMn and MATn bits in the PCA0CPMn register enables Software Timer mode.
Important Note About Capture/Compare Registers: When writing a 16-bit value to the PCA0 Capture/Compare
registers, the low byte should always be written first. Writing to PCA0CPLn clears the ECOMn bit to 0; writing to
PCA0CPHn sets ECOMn to 1.
PCA0CPLn
PCA0CPHn
MATn (Match Enable)
ECOMn
(Compare Enable)
PCA Clock
16-bit Comparator
PCA0L
match
PCA0H
Figure 20.3. PCA Software Timer Mode Diagram
150
Preliminary Rev 0.6
CCFn
(Interrupt Flag)
20.3.4. 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 automatically cleared by hardware when the CPU
vectors to the interrupt service routine, and must be cleared by software. Setting the TOGn, MATn, and ECOMn
bits in the PCA0CPMn register enables the High-Speed Output mode. If ECOMn is cleared, the associated pin will
retain its state, and not toggle on the next match event.
Important Note About Capture/Compare Registers: When writing a 16-bit value to the PCA0 Capture/Compare
registers, the low byte should always be written first. Writing to PCA0CPLn clears the ECOMn bit to 0; writing to
PCA0CPHn sets ECOMn to 1.
PCA0CPLn
PCA0CPHn
MATn (Match Enable)
ECOMn
(Compare Enable)
16-bit Comparator
match
CCFn
(Interrupt Flag)
Toggle
CEXn
PCA Clock
PCA0L
PCA0H
TOGn (Toggle Enable)
Figure 20.4. PCA High-Speed Output Mode Diagram
Preliminary Rev 0.6
151
Programmable Counter Array (PCA0)
C8051F85x/86x
Programmable Counter Array (PCA0)
C8051F85x/86x
20.3.5. 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 20.1.
F PCA
F CEXn = ----------------------------------------2  PCA0CPHn
Note: A value of 0x00 in the PCA0CPHn register is equal to 256 for this equation.
Equation 20.1. 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, n is toggled and
the offset held in the high byte is added to the matched value in PCA0CPLn. Frequency Output Mode is enabled by
setting the ECOMn, TOGn, and PWMn bits in the PCA0CPMn register. Note that the MATn bit should normally be
set to 0 in this mode. If the MATn bit is set to 1, the CCFn flag for the channel will be set when the 16-bit PCA0
counter and the 16-bit capture/compare register for the channel are equal.
PCA0CPLn
8-bit Adder
PCA0CPHn
Adder
Enable
Toggle
ECOMn
(Compare Enable)
8-bit
Comparator
match
CEXn
TOGn (Toggle Enable)
PCA Clock
PCA0L
Figure 20.5. PCA Frequency Output Mode
152
Preliminary Rev 0.6
20.4. PWM Waveform Generation
The PCA can generate edge or center-aligned PWM waveforms with resolutions of 8, 9, 10, 11 or 16 bits. PWM
resolution depends on the module setup, as sepcified within the individual module PCA0CPMn registers as well as
the PCA0PWM register. Modules can be configured for 8-11 bit mode, or for 16-bit mode individually using the
PCA0CPMn registers. All modules configured for 8-11 bit mode will have the same resolution, specified by the
PCA0PWM register. When operating in one of the PWM modes, each module may be individually configured for
center or edge-aligned PWM waveforms. Each channel has a single bit in the PCA0CENT register to select
between the two options.
20.4.1. Edge Aligned PWM
When configured for edge-aligned mode, a module will generate an edge transition at two points for every 2N PCA
clock cycles, where N is the selected PWM resolution in bits. In edge-aligned mode, these two edges are referred
to as the “match” and “overflow” edges. The polarity at the output pin is selectable, and can be inverted by setting
the appropriate channel bit to ‘1’ in the PCA0POL register. Prior to inversion, a match edge sets the channel to
logic high, and an overflow edge clears the channel to logic low.
The match edge occurs when the the lowest N bits of the module’s PCA0CPn register match the corresponding
bits of the main PCA0 counter register. For example, with 10-bit PWM, the match edge will occur any time bits 9-0
of the PCA0CPn register match bits 9-0 of the PCA0 counter value.
The overflow edge occurs when an overflow of the PCA0 counter happens at the desired resolution. For example,
with 10-bit PWM, the overflow edge will occur when bits 0-9 of the PCA0 counter transition from all 1’s to all 0’s. All
modules configured for edge-aligned mode at the same resolution will align on the overflow edge of the
waveforms.
An example of the PWM timing in edge-aligned mode for two channels is shown in Figure 20.6. In this example,
the CEX0POL and CEX1POL bits are cleared to 0.
PCA Clock
Counter (PCA0) 0xFFFF
0x0000
Capture / Compare
(PCA0CP0)
0x0001
0x0002
0x0003
0x0004
0x0005
0x0001
Output (CEX0)
match edge
Capture / Compare
(PCA0CP1)
0x0005
Output (CEX1)
overflow edge
match edge
Figure 20.6. Edge-Aligned PWM Timing
For a given PCA resolution, the unused high bits in the PCA0 counter and the PCA0CPn compare registers are
ignored, and only the used bits of the PCA0CPn register determine the duty cycle. Equation 20.2 describes the
duty cycle when CEXnPOL in the PCA0POL regsiter is cleared to 0. Equation 20.3 describes the duty cycle when
CEXnPOL in the PCA0POL regsiter is set to 1. A 0% duty cycle for the channel (with CEXnPOL = 0) is achieved by
Preliminary Rev 0.6
153
Programmable Counter Array (PCA0)
C8051F85x/86x
Programmable Counter Array (PCA0)
C8051F85x/86x
clearing the module’s ECOM bit to 0. This will disable the comparison, and prevent the match edge from occuring.
Note that although the PCA0CPn compare register determines the duty cycle, it is not always appropriate for
firmware to update this register directly. See the sections on 8 to 11-bit and 16-bit PWM mode for additional details
on adjusting duty cycle in the various modes.
N
 2 – PCA0CPn Duty Cycle = ----------------------------------------N
2
Equation 20.2. N-bit Edge-Aligned PWM Duty Cycle With CEXnPOL = 0 (N = PWM resolution)
PCA0CPn
Duty Cycle = -----------------------N
2
Equation 20.3. N-bit Edge-Aligned PWM Duty Cycle With CEXnPOL = 0 (N = PWM resolution)
154
Preliminary Rev 0.6
20.4.2. Center Aligned PWM
When configured for center-aligned mode, a module will generate an edge transition at two points for every 2(N+1)
PCA clock cycles, where N is the selected PWM resolution in bits. In center-aligned mode, these two edges are
referred to as the “up” and “down” edges. The polarity at the output pin is selectable, and can be inverted by setting
the appropriate channel bit to ‘1’ in the PCA0POL register.
The generated waveforms are centered about the points where the lower N bits of the PCA0 counter are zero. The
(N+1)th bit in the PCA0 counter acts as a selection between up and down edges. In 16-bit mode, a special 17th bit
is implemented internally for this purpose. At the center point, the (non-inverted) channel output will be low when
the (N+1)th bit is ‘0’ and high when the (N+1)th bit is ‘1’, except for cases of 0% and 100% duty cycle. Prior to
inversion, an up edge sets the channel to logic high, and a down edge clears the channel to logic low.
Down edges occur when the (N+1)th bit in the PCA0 counter is one, and a logical inversion of the value in the
module’s PCA0CPn register matches the main PCA0 counter register for the lowest N bits. For example, with 10bit PWM, the down edge will occur when the one’s complement of bits 9-0 of the PCA0CPn register match bits 9-0
of the PCA0 counter, and bit 10 of the PCA0 counter is ‘1’.
Up edges occur when the (N+1)th bit in the PCA0 counter is zero, and the lowest N bits of the module’s PCA0CPn
register match the value of (PCA0 - 1). For example, with 10-bit PWM, the up edge will occur when bits 9-0 of the
PCA0CPn register are one less than bits 9-0 of the PCA0 counter, and bit 10 of the PCA0 counter is ‘0’.
An example of the PWM timing in center-aligned mode for two channels is shown in Figure 20.7. In this example,
the CEX0POL and CEX1POL bits are cleared to 0.
center
PCA Clock
Counter (PCA0L)
0xFB
0xFC
0xFD
0xFE
0xFF
Capture / Compare
(PCA0CPL0)
0x00
0x01
0x02
0x03
0x04
0x01
center
Output (CEX0)
up edge
down edge
Capture / Compare
(PCA0CPL1)
0x04
center
Output (CEX1)
down edge
up edge
Figure 20.7. Center-Aligned PWM Timing
Equation 20.4 describes the duty cycle when CEXnPOL in the PCA0POL regsiter is cleared to 0. Equation 20.5
describes the duty cycle when CEXnPOL in the PCA0POL regsiter is set to 1. The equations are true only when
the lowest N bits of the PCA0CPn register are not all 0’s or all 1’s. With CEXnPOL equal to zero, 100% duty cycle
is produced when the lowest N bits of PCA0CPn are all 0, and 0% duty cycle is produced when the lowest N bits of
PCA0CPn are all 1. For a given PCA resolution, the unused high bits in the PCA0 counter and the PCA0CPn
compare registers are ignored, and only the used bits of the PCA0CPn register determine the duty cycle.
Preliminary Rev 0.6
155
Programmable Counter Array (PCA0)
C8051F85x/86x
Programmable Counter Array (PCA0)
C8051F85x/86x
Note that although the PCA0CPn compare register determines the duty cycle, it is not always appropriate for
firmware to update this register directly. See the sections on 8 to 11-bit and 16-bit PWM mode for additional details
on adjusting duty cycle in the various modes.
1
N
 2 – PCA0CPn  – --2
Duty Cycle = -------------------------------------------------N
2
Equation 20.4. N-bit Center-Aligned PWM Duty Cycle With CEXnPOL = 0 (N = PWM resolution)
1
PCA0CPn + --2
Duty Cycle = --------------------------------N
2
Equation 20.5. N-bit Center-Aligned PWM Duty Cycle With CEXnPOL = 1 (N = PWM resolution)
156
Preliminary Rev 0.6
20.4.3. 8 to11-bit Pulse Width Modulator Modes
Each module can be used independently to generate a pulse width modulated (PWM) output on its associated
CEXn pin. The frequency of the output is dependent on the timebase for the PCA counter/timer, and the setting of
the PWM cycle length (8 through 11-bits). For backwards-compatibility with the 8-bit PWM mode available on other
devices, the 8-bit PWM mode operates slightly different than 9 through 11-bit PWM modes. It is important to note
that all channels configured for 8 to 11-bit PWM mode will use the same cycle length. It is not possible to configure
one channel for 8-bit PWM mode and another for 11-bit mode (for example). However, other PCA channels can be
configured to Pin Capture, High-Speed Output, Software Timer, Frequency Output, or 16-bit PWM mode
independently. Each channel configured for a PWM mode can be individually selected to operate in edge-aligned
or center-aligned mode.
20.4.3.1. 8-bit Pulse Width Modulator Mode
In 8-bit PWM mode, the duty cycle is determined by the value of the low byte of the PCA0CPn register
(PCA0CPLn). To adjust the duty cycle, PCA0CPLn should not normally be written directly. Instead, it is
recommended to adjust the duty cycle using the high byte of the PCA0CPn register (register PCA0CPHn). This
allows seamless updating of the PWM waveform, as PCA0CPLn is reloaded automatically with the value stored in
PCA0CPHn during the overflow edge (in edge-aligned mode) or the up edge (in center-aligned mode).
Setting the ECOMn and PWMn bits in the PCA0CPMn register, and setting the CLSEL bits in register PCA0PWM
to 00b enables 8-Bit Pulse Width Modulator mode. If the MATn bit is set to 1, the CCFn flag for the module will be
set each time a match edge or up edge occurs. The COVF flag in PCA0PWM can be used to detect the overflow
(falling edge), which will occur every 256 PCA clock cycles.
20.4.3.2. 9 to 11-bit Pulse Width Modulator Mode
In 9 to 11-bit PWM mode, the duty cycle is determined by the value of the least significant N bits of the PCA0CPn
register, where N is the selected PWM resolution.
To adjust the duty cycle, PCA0CPn should not normally be written directly. Instead, it is recommended to adjust the
duty cycle by writing to an “Auto-Reload” register, which is dual-mapped into the PCA0CPHn and PCA0CPLn
register locations. The data written to define the duty cycle should be right-justified in the registers. The auto-reload
registers are accessed (read or written) when the bit ARSEL in PCA0PWM is set to 1. The capture/compare
registers are accessed when ARSEL is set to 0. This allows seamless updating of the PWM waveform, as the
PCA0CPn register is reloaded automatically with the value stored in the auto-reload registers during the overflow
edge (in edge-aligned mode) or the up edge (in center-aligned mode).
Setting the ECOMn and PWMn bits in the PCA0CPMn register, and setting the CLSEL bits in register PCA0PWM
to 00b enables 8-Bit Pulse Width Modulator mode. If the MATn bit is set to 1, the CCFn flag for the module will be
set each time a match edge or up edge occurs. The COVF flag in PCA0PWM can be used to detect the overflow or
down edge.
The 9 to 11-bit PWM mode is selected by setting the ECOMn and PWMn bits in the PCA0CPMn register, and
setting the CLSEL bits in register PCA0PWM to the desired cycle length (other than 8-bits). If the MATn bit is set to
1, the CCFn flag for the module will be set each time a match edge or up edge occurs. The COVF flag in
PCA0PWM can be used to detect the overflow or down edge.
Important Note About PCA0CPHn and PCA0CPLn Registers: When writing a 16-bit value to the PCA0CPn
registers, the low byte should always be written first. Writing to PCA0CPLn clears the ECOMn bit to 0; writing to
PCA0CPHn sets ECOMn to 1.
Preliminary Rev 0.6
157
Programmable Counter Array (PCA0)
C8051F85x/86x
Programmable Counter Array (PCA0)
C8051F85x/86x
20.4.4. 16-Bit Pulse Width Modulator Mode
A PCA module may also be operated in 16-Bit PWM mode. 16-bit PWM mode is independent of the other (8
through 11-bit) PWM modes. The entire PCA0CP register is used to determine the duty cycle in 16-bit PWM mode.
To output a varying duty cycle, new value writes should be synchronized with the PCA CCFn match flag to ensure
seamless updates.
16-Bit PWM mode is enabled by setting the ECOMn, PWMn, and PWM16n bits in the PCA0CPMn register. For a
varying duty cycle, the match interrupt flag 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
match edge or up edge occurs. The CF flag in PCA0CN can be used to detect the overflow or down edge.
Important Note About Capture/Compare Registers: When writing a 16-bit value to the PCA0 Capture/Compare
registers, the low byte should always be written first. Writing to PCA0CPLn clears the ECOMn bit to 0; writing to
PCA0CPHn sets ECOMn to 1.
158
Preliminary Rev 0.6
20.5. Comparator Clear Function
In 8/9/10/11/16-bit PWM modes, the comparator clear function utilizes the Comparator0 output synchronized to the
system clock to clear CEXn to logic low for the current PWM cycle. This comparator clear function can be enabled
for each PWM channel by setting the CPCEn bits to 1 in the PCA0CLR SFR. When the comparator clear function
is disabled, CEXn is unaffected.
The asynchronous Comparator 0 output is logic high when the voltage of CP0+ is greater than CP0- and logic low
when the voltage of CP0+ is less than CP0-. The polarity of the Comparator 0 output is used to clear CEXn as
follows: when CPCPOL = 0, CEXn is cleared on the falling edge of the Comparator0 output (see Figure 20.8);
when CPCPOL = 1, CEXn is cleared on the rising edge of the Compartor0 output (see Figure 20.9).
CEXn (CPCEn = 0)
Comparator0 Output
(CPCPOL = 0)
CEXn (CPCEn = 1)
Figure 20.8. CEXn with CPCEn = 1, CPCPOL = 0
CEXn (CPCEn = 0)
Comparator0 Output
(CPCPOL = 1)
CEXn (CPCEn = 1)
Figure 20.9. CEXn with CPCEn = 1, CPCPOL = 1
In the PWM cycle following the current cycle, should the Comparator 0 output remain logic low when CPCPOL = 0
or logic high when CPCPOL = 1, CEXn will continue to be cleared. See Figure 20.10 and Figure 20.11.
CEXn (CPCEn = 0)
Comparator0 Output
(CPCPOL = 0)
CEXn (CPCEn = 1)
Figure 20.10. CEXn with CPCEn = 1, CPCPOL = 0
CEXn (CPCEn = 0)
Comparator0 Output
(CPCPOL = 1)
CEXn (CPCEn = 1)
Figure 20.11. CEXn with CPCEn = 1, CPCPOL = 1
Preliminary Rev 0.6
159
Programmable Counter Array (PCA0)
C8051F85x/86x
Programmable Counter Array (PCA0)
C8051F85x/86x
20.6. PCA Control Registers
Register 20.1. PCA0CN: PCA Control
Bit
7
6
5
Name
CF
CR
Type
RW
RW
Reset
0
0
4
0
3
2
1
0
Reserved
CCF2
CCF1
CCF0
R
RW
RW
RW
0
0
0
0
0
SFR Address: 0xD8 (bit-addressable)
Table 20.3. PCA0CN Register Bit Descriptions
Bit
Name
7
CF
Function
PCA Counter/Timer Overflow Flag.
Set by hardware when the PCA Counter/Timer overflows from 0xFFFF to 0x0000. When
the Counter/Timer Overflow (CF) interrupt is enabled, setting this bit causes the CPU to
vector to the PCA interrupt service routine. This bit is not automatically cleared by hardware and must be cleared by software.
6
CR
PCA Counter/Timer Run Control.
This bit enables/disables the PCA Counter/Timer.
0: PCA Counter/Timer disabled.
1: PCA Counter/Timer enabled.
5:3
Reserved
2
CCF2
Must write reset value.
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 routine.
This bit is not automatically cleared by hardware and must be cleared by software.
1
CCF1
PCA Module 1 Capture/Compare Flag.
This bit is set by hardware when a match or capture occurs. When the CCF1 interrupt is
enabled, setting this bit causes the CPU to vector to the PCA interrupt service routine.
This bit is not automatically cleared by hardware and must be cleared by software.
0
CCF0
PCA Module 0 Capture/Compare Flag.
This bit is set by hardware when a match or capture occurs. When the CCF0 interrupt is
enabled, setting this bit causes the CPU to vector to the PCA interrupt service routine.
This bit is not automatically cleared by hardware and must be cleared by software.
160
Preliminary Rev 0.6
Register 20.2. PCA0MD: PCA Mode
Bit
7
6
Name
CIDL
Reserved
CPS
ECF
Type
RW
R
RW
RW
Reset
0
0
5
4
0
3
0
0
2
0
1
0
0
0
SFR Address: 0xD9
Table 20.4. PCA0MD Register Bit Descriptions
Bit
Name
7
CIDL
Function
PCA Counter/Timer Idle Control.
Specifies PCA behavior when CPU is in Idle Mode.
0: PCA continues to function normally while the system controller is in Idle Mode.
1: PCA operation is suspended while the system controller is in Idle Mode.
6:4
Reserved
3:1
CPS
Must write reset value.
PCA Counter/Timer Pulse Select.
These bits select the timebase source for the PCA counter.
000: System clock divided by 12.
001: System clock divided by 4.
010: Timer 0 overflow.
011: High-to-low transitions on ECI (max rate = system clock divided by 4).
100: System clock.
101: External clock divided by 8 (synchronized with the system clock).
110: Low frequency oscillator divided by 8.
111: Reserved.
0
ECF
PCA Counter/Timer Overflow Interrupt Enable.
This bit sets the masking of the PCA Counter/Timer Overflow (CF) interrupt.
0: Disable the CF interrupt.
1: Enable a PCA Counter/Timer Overflow interrupt request when CF (PCA0CN.7) is set.
Preliminary Rev 0.6
161
Programmable Counter Array (PCA0)
C8051F85x/86x
Programmable Counter Array (PCA0)
C8051F85x/86x
Register 20.3. PCA0PWM: PCA PWM Configuration
Bit
7
6
5
4
3
Name
ARSEL
ECOV
COVF
Reserved
CLSEL
Type
RW
RW
RW
R
RW
Reset
0
0
0
0
0
2
0
1
0
0
0
SFR Address: 0xF7
Table 20.5. PCA0PWM Register Bit Descriptions
Bit
Name
7
ARSEL
Function
Auto-Reload Register Select.
This bit selects whether to read and write the normal PCA capture/compare registers
(PCA0CPn), or the Auto-Reload registers at the same SFR addresses. This function is
used to define the reload value for 9 to 11-bit PWM modes. In all other modes, the AutoReload registers have no function.
0: Read/Write Capture/Compare Registers at PCA0CPHn and PCA0CPLn.
1: Read/Write Auto-Reload Registers at PCA0CPHn and PCA0CPLn.
6
ECOV
Cycle Overflow Interrupt Enable.
This bit sets the masking of the Cycle Overflow Flag (COVF) interrupt.
0: COVF will not generate PCA interrupts.
1: A PCA interrupt will be generated when COVF is set.
5
COVF
Cycle Overflow Flag.
This bit indicates an overflow of the 8th to 11th bit of the main PCA counter (PCA0). The
specific bit used for this flag depends on the setting of the Cycle Length Select bits. The
bit can be set by hardware or software, but must be cleared by software.
0: No overflow has occurred since the last time this bit was cleared.
1: An overflow has occurred since the last time this bit was cleared.
4:3
Reserved
Must write reset value.
2:0
CLSEL
Cycle Length Select.
When 16-bit PWM mode is not selected, these bits select the length of the PWM cycle.
This affects all channels configured for PWM which are not using 16-bit PWM mode.
These bits are ignored for individual channels configured to16-bit PWM mode.
000: 8 bits.
001: 9 bits.
010: 10 bits.
011: 11 bits.
100-111: Reserved.
162
Preliminary Rev 0.6
Register 20.4. PCA0CLR: PCA Comparator Clear Control
Bit
7
Name
CPCPOL
Type
RW
Reset
0
6
0
5
4
2
1
0
Reserved
CPCE2
CPCE1
CPCE0
R
RW
RW
RW
0
0
0
0
3
0
0
SFR Address: 0x9C
Table 20.6. PCA0CLR Register Bit Descriptions
Bit
Name
7
CPCPOL
Function
Comparator Clear Polarity.
Selects the polarity of the comparator result that will clear the PCA channel(s).
0: PCA channel(s) will be cleared when comparator result goes logic low.
1: PCA channel(s) will be cleared when comparator result goes logic high.
6:3
Reserved
2
CPCE2
Must write reset value.
Comparator Clear Enable for CEX2.
Enables the comparator clear function on PCA channel 2.
1
CPCE1
Comparator Clear Enable for CEX1.
Enables the comparator clear function on PCA channel 1.
0
CPCE0
Comparator Clear Enable for CEX0.
Enables the comparator clear function on PCA channel 0.
Preliminary Rev 0.6
163
Programmable Counter Array (PCA0)
C8051F85x/86x
Programmable Counter Array (PCA0)
C8051F85x/86x
Register 20.5. PCA0CPM0: PCA Capture/Compare Mode
Bit
7
6
5
4
3
2
1
0
Name
PWM16
ECOM
CAPP
CAPN
MAT
TOG
PWM
ECCF
Type
RW
RW
RW
RW
RW
RW
RW
RW
Reset
0
0
0
0
0
0
0
0
SFR Address: 0xDA
Table 20.7. PCA0CPM0 Register Bit Descriptions
Bit
Name
7
PWM16
Function
16-bit Pulse Width Modulation Enable.
This bit enables 16-bit mode when Pulse Width Modulation mode is enabled.
0: 8 to 11-bit PWM selected.
1: 16-bit PWM selected.
6
ECOM
Comparator Function Enable.
This bit enables the comparator function.
5
CAPP
Capture Positive Function Enable.
This bit enables the positive edge capture capability.
4
CAPN
Capture Negative Function Enable.
This bit enables the negative edge capture capability.
3
MAT
Match Function Enable.
This bit enables the match function. When enabled, matches of the PCA counter with a
module's capture/compare register cause the CCF0 bit in the PCA0MD register to be set
to logic 1.
2
TOG
Toggle Function Enable.
This bit enables the toggle function. When enabled, matches of the PCA counter with the
capture/compare register cause the logic level on the CEX0 pin to toggle. If the PWM bit
is also set to logic 1, the module operates in Frequency Output Mode.
1
PWM
Pulse Width Modulation Mode Enable.
This bit enables the PWM function. When enabled, a pulse width modulated signal is output on the CEX0 pin. 8 to 11-bit PWM is used if PWM16 is cleared; 16-bit mode is used if
PWM16 is set to logic 1. If the TOG bit is also set, the module operates in Frequency
Output Mode.
0
ECCF
Capture/Compare Flag Interrupt Enable.
This bit sets the masking of the Capture/Compare Flag (CCF0) interrupt.
0: Disable CCF0 interrupts.
1: Enable a Capture/Compare Flag interrupt request when CCF0 is set.
164
Preliminary Rev 0.6
Register 20.6. PCA0L: PCA Counter/Timer Low Byte
Bit
7
6
5
4
Name
PCA0L
Type
RW
Reset
0
0
0
0
3
2
1
0
0
0
0
0
SFR Address: 0xF9
Table 20.8. PCA0L Register Bit Descriptions
Bit
Name
7:0
PCA0L
Function
PCA Counter/Timer Low Byte.
The PCA0L register holds the low byte (LSB) of the 16-bit PCA Counter/Timer.
Preliminary Rev 0.6
165
Programmable Counter Array (PCA0)
C8051F85x/86x
Programmable Counter Array (PCA0)
C8051F85x/86x
Register 20.7. PCA0H: PCA Counter/Timer High Byte
Bit
7
6
5
4
Name
PCA0H
Type
RW
Reset
0
0
0
0
3
2
1
0
0
0
0
0
SFR Address: 0xFA
Table 20.9. PCA0H Register Bit Descriptions
Bit
Name
7:0
PCA0H
Function
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.
166
Preliminary Rev 0.6
Register 20.8. PCA0CPL0: PCA Capture Module Low Byte
Bit
7
6
5
4
Name
PCA0CPL0
Type
RW
Reset
0
0
0
0
3
2
1
0
0
0
0
0
SFR Address: 0xFB
Table 20.10. PCA0CPL0 Register Bit Descriptions
Bit
7:0
Name
Function
PCA0CPL0 PCA Capture Module Low Byte.
The PCA0CPL0 register holds the low byte (LSB) of the 16-bit capture module.This register address also allows access to the low byte of the corresponding PCA channels
auto-reload value for 9 to 11-bit PWM mode. The ARSEL bit in register PCA0PWM controls which register is accessed.
Note: A write to this register will clear the modules ECOM bit to a 0.
Preliminary Rev 0.6
167
Programmable Counter Array (PCA0)
C8051F85x/86x
Programmable Counter Array (PCA0)
C8051F85x/86x
Register 20.9. PCA0CPH0: PCA Capture Module High Byte
Bit
7
6
5
4
3
Name
PCA0CPH0
Type
RW
Reset
0
0
0
0
0
2
1
0
0
0
0
SFR Address: 0xFC
Table 20.11. PCA0CPH0 Register Bit Descriptions
Bit
7:0
Name
Function
PCA0CPH0 PCA Capture Module High Byte.
The PCA0CPH0 register holds the high byte (MSB) of the 16-bit capture module.This
register address also allows access to the high byte of the corresponding PCA channels
auto-reload value for 9 to 11-bit PWM mode. The ARSEL bit in register PCA0PWM controls which register is accessed.
Note: A write to this register will set the modules ECOM bit to a 1.
168
Preliminary Rev 0.6
Register 20.10. PCA0POL: PCA Output Polarity
Bit
7
6
5
4
3
2
1
0
Name
Reserved
CEX2POL
CEX1POL
CEX0POL
Type
R
RW
RW
RW
0
0
0
Reset
0
0
0
0
0
SFR Address: 0x96
Table 20.12. PCA0POL Register Bit Descriptions
Bit
Name
Function
7:3
Reserved
Must write reset value.
2
CEX2POL
CEX2 Output Polarity.
Selects the polarity of the CEX2 output channel. When this bit is modified, the change
takes effect at the pin immediately.
0: Use default polarity.
1: Invert polarity.
1
CEX1POL
CEX1 Output Polarity.
Selects the polarity of the CEX1 output channel. When this bit is modified, the change
takes effect at the pin immediately.
0: Use default polarity.
1: Invert polarity.
0
CEX0POL
CEX0 Output Polarity.
Selects the polarity of the CEX0 output channel. When this bit is modified, the change
takes effect at the pin immediately.
0: Use default polarity.
1: Invert polarity.
Preliminary Rev 0.6
169
Programmable Counter Array (PCA0)
C8051F85x/86x
Programmable Counter Array (PCA0)
C8051F85x/86x
Register 20.11. PCA0CENT: PCA Center Alignment Enable
Bit
7
6
5
4
3
2
1
0
Name
Reserved
CEX2CEN
CEX1CEN
CEX0CEN
Type
R
RW
RW
RW
0
0
0
Reset
0
0
0
0
0
SFR Address: 0x9E
Table 20.13. PCA0CENT Register Bit Descriptions
Bit
Name
Function
7:3
Reserved
Must write reset value.
2
CEX2CEN
CEX2 Center Alignment Enable.
Selects the alignment properties of the CEX2 output channel when operated in any of the
PWM modes. This bit does not affect the operation of non-PWM modes.
0: Edge-aligned.
1: Center-aligned.
1
CEX1CEN
CEX1 Center Alignment Enable.
Selects the alignment properties of the CEX1 output channel when operated in any of the
PWM modes. This bit does not affect the operation of non-PWM modes.
0: Edge-aligned.
1: Center-aligned.
0
CEX0CEN
CEX0 Center Alignment Enable.
Selects the alignment properties of the CEX0 output channel when operated in any of the
PWM modes. This bit does not affect the operation of non-PWM modes.
0: Edge-aligned.
1: Center-aligned.
170
Preliminary Rev 0.6
Register 20.12. PCA0CPM1: PCA Capture/Compare Mode
Bit
7
6
5
4
3
2
1
0
Name
PWM16
ECOM
CAPP
CAPN
MAT
TOG
PWM
ECCF
Type
RW
RW
RW
RW
RW
RW
RW
RW
Reset
0
0
0
0
0
0
0
0
SFR Address: 0xDB
Table 20.14. PCA0CPM1 Register Bit Descriptions
Bit
Name
7
PWM16
Function
16-bit Pulse Width Modulation Enable.
This bit enables 16-bit mode when Pulse Width Modulation mode is enabled.
0: 8 to 11-bit PWM selected.
1: 16-bit PWM selected.
6
ECOM
Comparator Function Enable.
This bit enables the comparator function.
5
CAPP
Capture Positive Function Enable.
This bit enables the positive edge capture capability.
4
CAPN
Capture Negative Function Enable.
This bit enables the negative edge capture capability.
3
MAT
Match Function Enable.
This bit enables the match function. When enabled, matches of the PCA counter with a
module's capture/compare register cause the CCF1 bit in the PCA0MD register to be set
to logic 1.
2
TOG
Toggle Function Enable.
This bit enables the toggle function. When enabled, matches of the PCA counter with the
capture/compare register cause the logic level on the CEX1 pin to toggle. If the PWM bit
is also set to logic 1, the module operates in Frequency Output Mode.
1
PWM
Pulse Width Modulation Mode Enable.
This bit enables the PWM function. When enabled, a pulse width modulated signal is output on the CEX1 pin. 8 to 11-bit PWM is used if PWM16 is cleared; 16-bit mode is used if
PWM16 is set to logic 1. If the TOG bit is also set, the module operates in Frequency
Output Mode.
0
ECCF
Capture/Compare Flag Interrupt Enable.
This bit sets the masking of the Capture/Compare Flag (CCF1) interrupt.
0: Disable CCF1 interrupts.
1: Enable a Capture/Compare Flag interrupt request when CCF1 is set.
Preliminary Rev 0.6
171
Programmable Counter Array (PCA0)
C8051F85x/86x
Programmable Counter Array (PCA0)
C8051F85x/86x
Register 20.13. PCA0CPM2: PCA Capture/Compare Mode
Bit
7
6
5
4
3
2
1
0
Name
PWM16
ECOM
CAPP
CAPN
MAT
TOG
PWM
ECCF
Type
RW
RW
RW
RW
RW
RW
RW
RW
Reset
0
0
0
0
0
0
0
0
SFR Address: 0xDC
Table 20.15. PCA0CPM2 Register Bit Descriptions
Bit
Name
7
PWM16
Function
16-bit Pulse Width Modulation Enable.
This bit enables 16-bit mode when Pulse Width Modulation mode is enabled.
0: 8 to 11-bit PWM selected.
1: 16-bit PWM selected.
6
ECOM
Comparator Function Enable.
This bit enables the comparator function.
5
CAPP
Capture Positive Function Enable.
This bit enables the positive edge capture capability.
4
CAPN
Capture Negative Function Enable.
This bit enables the negative edge capture capability.
3
MAT
Match Function Enable.
This bit enables the match function. When enabled, matches of the PCA counter with a
module's capture/compare register cause the CCF2 bit in the PCA0MD register to be set
to logic 1.
2
TOG
Toggle Function Enable.
This bit enables the toggle function. When enabled, matches of the PCA counter with the
capture/compare register cause the logic level on the CEX2 pin to toggle. If the PWM bit
is also set to logic 1, the module operates in Frequency Output Mode.
1
PWM
Pulse Width Modulation Mode Enable.
This bit enables the PWM function. When enabled, a pulse width modulated signal is output on the CEX2 pin. 8 to 11-bit PWM is used if PWM16 is cleared; 16-bit mode is used if
PWM16 is set to logic 1. If the TOG bit is also set, the module operates in Frequency
Output Mode.
0
ECCF
Capture/Compare Flag Interrupt Enable.
This bit sets the masking of the Capture/Compare Flag (CCF2) interrupt.
0: Disable CCF2 interrupts.
1: Enable a Capture/Compare Flag interrupt request when CCF2 is set.
172
Preliminary Rev 0.6
Register 20.14. PCA0CPL1: PCA Capture Module Low Byte
Bit
7
6
5
4
Name
PCA0CPL1
Type
RW
Reset
0
0
0
0
3
2
1
0
0
0
0
0
SFR Address: 0xE9
Table 20.16. PCA0CPL1 Register Bit Descriptions
Bit
7:0
Name
Function
PCA0CPL1 PCA Capture Module Low Byte.
The PCA0CPL1 register holds the low byte (LSB) of the 16-bit capture module.This register address also allows access to the low byte of the corresponding PCA channels
auto-reload value for 9 to 11-bit PWM mode. The ARSEL bit in register PCA0PWM controls which register is accessed.
Note: A write to this register will clear the modules ECOM bit to a 0.
Preliminary Rev 0.6
173
Programmable Counter Array (PCA0)
C8051F85x/86x
Programmable Counter Array (PCA0)
C8051F85x/86x
Register 20.15. PCA0CPH1: PCA Capture Module High Byte
Bit
7
6
5
4
3
Name
PCA0CPH1
Type
RW
Reset
0
0
0
0
0
2
1
0
0
0
0
SFR Address: 0xEA
Table 20.17. PCA0CPH1 Register Bit Descriptions
Bit
7:0
Name
Function
PCA0CPH1 PCA Capture Module High Byte.
The PCA0CPH1 register holds the high byte (MSB) of the 16-bit capture module.This
register address also allows access to the high byte of the corresponding PCA channels
auto-reload value for 9 to 11-bit PWM mode. The ARSEL bit in register PCA0PWM controls which register is accessed.
Note: A write to this register will set the modules ECOM bit to a 1.
174
Preliminary Rev 0.6
Register 20.16. PCA0CPL2: PCA Capture Module Low Byte
Bit
7
6
5
4
Name
PCA0CPL2
Type
RW
Reset
0
0
0
0
3
2
1
0
0
0
0
0
SFR Address: 0xEB
Table 20.18. PCA0CPL2 Register Bit Descriptions
Bit
7:0
Name
Function
PCA0CPL2 PCA Capture Module Low Byte.
The PCA0CPL2 register holds the low byte (LSB) of the 16-bit capture module.This register address also allows access to the low byte of the corresponding PCA channels
auto-reload value for 9 to 11-bit PWM mode. The ARSEL bit in register PCA0PWM controls which register is accessed.
Note: A write to this register will clear the modules ECOM bit to a 0.
Preliminary Rev 0.6
175
Programmable Counter Array (PCA0)
C8051F85x/86x
Programmable Counter Array (PCA0)
C8051F85x/86x
Register 20.17. PCA0CPH2: PCA Capture Module High Byte
Bit
7
6
5
4
3
Name
PCA0CPH2
Type
RW
Reset
0
0
0
0
0
2
1
0
0
0
0
SFR Address: 0xEC
Table 20.19. PCA0CPH2 Register Bit Descriptions
Bit
7:0
Name
Function
PCA0CPH2 PCA Capture Module High Byte.
The PCA0CPH2 register holds the high byte (MSB) of the 16-bit capture module.This
register address also allows access to the high byte of the corresponding PCA channels
auto-reload value for 9 to 11-bit PWM mode. The ARSEL bit in register PCA0PWM controls which register is accessed.
Note: A write to this register will set the modules ECOM bit to a 1.
176
Preliminary Rev 0.6
Port I/O (Port 0, Port 1, Port 2, Crossbar, and Port Match)
C8051F85x/86x
21. Port I/O (Port 0, Port 1, Port 2, Crossbar, and Port Match)
Digital and analog resources on the C8051F85x/86x family are externally available on the device’s multi-purpose I/
O pins. Port pins P0.0-P1.7 can be defined as general-purpose I/O (GPIO), assigned to one of the internal digital
resources through the crossbar, or assigned to an analog function. Port pins P2.0 and P2.1 can be used as GPIO.
Port pin P2.0 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 priority crossbar decoder. Note that the state of a port I/O pin can always be read in
the corresponding port latch, regardless of the crossbar settings.
The crossbar assigns the selected internal digital resources to the I/O pins based on the Priority Decoder
(Figure 21.2 and Figure 21.3). The registers XBR0, XBR1 and XBR2 are used to select internal digital functions.
The port I/O cells are configured as either push-pull or open-drain in the Port Output Mode registers (PnMDOUT,
where n = 0,1). Additionally, each bank of port pins (P0, P1, and P2) have two selectable drive strength settings.
UART0
SPI0
SMBus0
CMP0 Out
CMP1 Out
SYSCLK
PCA (CEXn)
PCA (ECI)
Timer 0
Timer 1
Timer 2
2
4
Priority Crossbar
Decoder
2
Port 0
Control
&
Config
P0.0 / VREF
P0.1 / AGND
P0.2
P0.3 / EXTCLK
P0.4
P0.5
P0.6 / CNVSTR
P0.7
Port 1
Control
&
Config
P1.0
P1.1
P1.2
P1.3
P1.4
P1.5
P1.6
P1.7
Port 2
Control
&
Config
P2.0 / C2D
P2.1
2
2
1
3
1
1
1
ADC0 In
CMP0/1 In
Port Match
INT0 / INT1
1
Figure 21.1. Port I/O Functional Block Diagram
178
Preliminary Rev 0.6
21.1. General Port I/O Initialization
Port I/O initialization consists of the following steps:
1. Select the input mode (analog or digital) for all port pins, using the Port Input Mode register (PnMDIN).
2. Select the output mode (open-drain or push-pull) for all port pins, using the Port Output Mode register
(PnMDOUT).
3. Select any pins to be skipped by the I/O crossbar using the Port Skip registers (PnSKIP).
4. Assign port pins to desired peripherals.
5. Enable the crossbar (XBARE = ‘1’).
All port pins must be configured as either analog or digital inputs. Any pins to be used as Comparator or ADC
inputs should be configured as an analog inputs. When a pin is configured as an analog input, its weak pullup,
digital driver, and digital receiver are disabled. This process saves power and reduces noise on the analog input.
Pins configured as digital inputs may still be used by analog peripherals; however this practice is not
recommended.
Additionally, all analog input pins should be configured to be skipped by the crossbar (accomplished by setting the
associated bits in PnSKIP). Port input mode is set in the PnMDIN register, where a ‘1’ indicates a digital input, and
a ‘0’ indicates an analog input. All pins default to digital inputs on reset.
The output driver characteristics of the I/O pins are defined using the Port Output Mode registers (PnMDOUT).
Each port output driver can be configured as either open drain or push-pull. This selection is required even for the
digital resources selected in the XBRn registers, and is not automatic. The only exception to this is the SMBus
(SDA, SCL) pins, which are configured as open-drain regardless of the PnMDOUT settings. When the WEAKPUD
bit in XBR1 is ‘0’, a weak pullup is enabled for all Port I/O configured as open-drain. WEAKPUD does not affect the
push-pull Port I/O. Furthermore, the weak pullup is turned off on an output that is driving a ‘0’ to avoid unnecessary
power dissipation.
Registers XBR0 and XBR1 must be loaded with the appropriate values to select the digital I/O functions required
by the design. Setting the XBARE bit in 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; as an alternative,
Silicon Labs provides configuration utility software to determine the port I/O pin-assignments based on the
crossbar register settings.
The crossbar must be enabled to use port pins as standard port I/O in output mode. Port output drivers of all
crossbar pins are disabled whenever the crossbar is disabled.
Preliminary Rev 0.6
179
Port I/O (Port 0, Port 1, Port 2, Crossbar, and Port Match)
C8051F85x/86x
Port I/O (Port 0, Port 1, Port 2, Crossbar, and Port Match)
C8051F85x/86x
21.2. 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
analog functions should be configured for analog I/O, and port pins assigned to digital or external interrupt
functions should be configured for digital I/O.
21.2.1. Assigning Port I/O Pins to Analog Functions
Table 21.1 shows all available analog functions that require port I/O assignments. Table 21.1 shows the potential
mapping of port I/O to each analog function.
Table 21.1. Port I/O Assignment for Analog Functions
Analog Function
Potentially Assignable
Port Pins
SFR(s) used for
Assignment
ADC Input
P0.0 - P1.7
AMX0P, AMX0N,
PnSKIP, PnMDIN
Comparator0 Input
P0.0 - P1.7
CPT0MX, PnSKIP,
PnMDIN
Comparator1 Input
P0.0 - P1.7
CPT1MX, PnSKIP,
PnMDIN
Voltage Reference (VREF)
P0.0
REF0CN, PnSKIP,
PnMDIN
Reference Ground (AGND)
P0.1
REF0CN, PnSKIP,
PnMDIN
21.2.2. Assigning Port I/O Pins to Digital Functions
Any port pins not assigned to analog functions may be assigned to digital functions or used as GPIO. Most digital
functions rely on the crossbar for pin assignment; however, some digital functions bypass the crossbar in a manner
similar to the analog functions listed above. Table 21.2 shows all digital functions available through the crossbar
and the potential mapping of port I/O to each function.
Table 21.2. Port I/O Assignment for Digital Functions
Digital Function
Potentially Assignable Port Pins
UART0, SPI0, SMBus0, CP0, CP0A, Any port pin available for assignment by the
CP1, CP1A, SYSCLK, PCA0 (CEX0- crossbar. This includes P0.0 - P1.7 pins which
2 and ECI), T0, T1 or T2.
have their PnSKIP bit set to ‘0’.
Note: The crossbar will always assign UART0
pins to P0.4 and P0.5.
Any pin used for GPIO
180
P0.0 - P2.1
Preliminary Rev 0.6
SFR(s) Used for
Assignment
XBR0, XBR1, XBR2
P0SKIP, P1SKIP,
P2SKIP
21.2.3. Assigning Port I/O Pins to Fixed Digital Functions
Fixed digital functions include external clock input as well as external event trigger functions, which can be used to
trigger events such as an ADC conversion, fire an interrupt or wake the device from idle mode when a transition
occurs on a digital I/O pin. The fixed digital functions do not require dedicated pins and will function on both GPIO
pins and pins in use by the crossbar. Fixed digital functions cannot be used on pins configured for analog I/O.
Table 21.3 shows all available fixed digital functions and the potential mapping of port I/O to each function.
Table 21.3. Port I/O Assignment for Fixed Digital Functions
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
Conversion Start (CNVSTR)
P0.6
ADC0CN
External Clock Input (EXTCLK)
P0.3
OSCXCN
P0.0 - P1.7
P0MASK, P0MAT
P1MASK, P1MAT
Port Match
Preliminary Rev 0.6
181
Port I/O (Port 0, Port 1, Port 2, Crossbar, and Port Match)
C8051F85x/86x
21.3. Priority Crossbar Decoder
The priority crossbar decoder 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 PnSKIP registers
are set. The PnSKIP registers allow software to skip port pins that are to be used for analog input, dedicated
functions, or GPIO.
Important Note on Crossbar Configuration: If a port pin is claimed by a peripheral without use of the crossbar,
its corresponding PnSKIP bit should be set. This applies to P0.0 if VREF is used, P0.1 if AGND is used, P0.3 if the
EXTCLK input 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 21.2 shows all of the potential peripheral-to-pin assignments available to the crossbar. Note that this does
not mean any peripheral can always be assigned to the highlighted pins. The actual pin assignments are
determined by the priority of the enabled peripherals.
5
0
0
6
7
0
1
2
0
0
0
0
3
EXTCLK
QFN-20 Package
CNVSTR
SOIC-16 Package
QSOP-24 Package
P2
4
5
6
0
0
0
7
0
1
N/A
0
P1
4
C2D
0
3
N/A
2
N/A
1
N/A
P0
0
N/A
Port
Pin Number
VREF
UART0-TX
UART0-RX
SPI0-SCK
SPI0-MISO
SPI0-MOSI
SPI0-NSS*
SMB0-SDA
Pins Not Available on Crossbar
Port I/O (Port 0, Port 1, Port 2, Crossbar, and Port Match)
C8051F85x/86x
SMB0-SCL
CMP0-CP0
CMP0-CP0A
CMP1-CP1
CMP1-CP1A
SYSCLK
PCA0-CEX0
PCA0-CEX1
PCA0-CEX2
PCA0-ECI
Timer0-T0
Timer1-T1
Timer2-T2
Pin Skip Settings
0
0
0
P0SKIP
0
0
P1SKIP
The crossbar peripherals are assigned in priority order from top to bottom.
These boxes represent Port 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 can be “skipped” by setting the corresponding bit in PnSKIP to 1.
* NSS is only pinned out when the SPI is in 4-wire mode.
Figure 21.2. Crossbar Priority Decoder - Possible Pin Assignments
182
Preliminary Rev 0.6
Registers XBR0, 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);
when UART0 is selected, the crossbar assigns both pins associated with UART0 (TX and RX). UART0 pin
assignments are fixed for bootloading purposes: UART0 TX is always assigned to P0.4; UART0 RX is always
assigned to P0.5. Standard port I/Os appear contiguously after the prioritized functions have been assigned.
Figure 21.3 shows an example of the resulting pin assignments of the device with UART0 and SPI0 enabled and
the EXTCLK (P0.3) pin skipped (P0SKIP = 0x08). UART0 is the highest priority and it will be assigned first. The
UART0 pins can only appear on P0.4 and P0.5, so that is where it is assigned. The next-highest enabled peripheral
is SPI0. P0.0, P0.1 and P0.2 are free, so SPI0 takes these three pins. The fourth pin, NSS, is routed to P0.6
because P0.3 is skipped and P0.4 and P0.5 are already occupied by the UART. The other pins on the device are
available for use as general-purpose digital I/O or analog functions.
5
0
0
6
7
0
1
2
0
0
0
0
3
EXTCLK
VREF
QFN-20 Package
CNVSTR
SOIC-16 Package
QSOP-24 Package
P2
4
5
6
0
0
0
7
0
1
N/A
0
P1
4
C2D
0
3
N/A
2
N/A
1
N/A
P0
0
N/A
Port
Pin Number
UART0-TX
UART0-RX
SPI0-SCK
SPI0-MISO
SPI0-MOSI
SPI0-NSS*
Pins Not Available on Crossbar
SMB0-SDA
SMB0-SCL
CMP0-CP0
CMP0-CP0A
CMP1-CP1
CMP1-CP1A
SYSCLK
PCA0-CEX0
PCA0-CEX1
PCA0-CEX2
PCA0-ECI
Timer0-T0
Timer1-T1
Timer2-T2
Pin Skip Settings
0
1
0
P0SKIP
0
0
P1SKIP
The crossbar peripherals are assigned in priority order from top to bottom.
These boxes represent Port 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 can be “skipped” by setting the corresponding bit in PnSKIP to 1.
* NSS is only pinned out when the SPI is in 4-wire mode.
Figure 21.3. Crossbar Priority Decoder Example
Note: The SPI can be operated in either 3-wire or 4-wire modes, pending the state of the NSSMD1–NSSMD0 bits
in register SPI0CN. According to the SPI mode, the NSS signal may or may not be routed to a port pin. The order
in which SMBus pins are assigned is defined by the SWAP bit in the SMB0TC register.
Preliminary Rev 0.6
183
Port I/O (Port 0, Port 1, Port 2, Crossbar, and Port Match)
C8051F85x/86x
Port I/O (Port 0, Port 1, Port 2, Crossbar, and Port Match)
C8051F85x/86x
21.4. Port I/O Modes of Operation
Port pins are configured by firmware as digital or analog I/O using the PnMDIN registers. On reset, all port I/O cells
default to a high impedance state with weak pull-ups enabled. Until the crossbar is enabled, both the high and low
port I/O drive circuits are explicitly disabled on all crossbar pins. Port pins configured as digital I/O may still be used
by analog peripherals; however, this practice is not recommended and may result in measurement errors.
21.4.1. Configuring Port Pins For Analog Modes
Any pins to be used for analog functions should be configured for analog mode. When a pin is configured for
analog I/O, its weak pullup, digital driver, and digital receiver are disabled. Port pins configured for analog functions
will always read back a value of ‘0’ in the corresponding Pn Port Latch register. To configure a pin as analog, the
following steps should be taken:
1. Clear the bit associated with the pin in the PnMDIN register to ‘0’. This selects analog mode for the pin.
2. Set the bit associated with the pin in the Pn register to ‘1’.
3. Skip the bit associated with the pin in the PnSKIP register to ensure the crossbar does not attempt to
assign a function to the pin.
21.4.2. Configuring Port Pins For Digital Modes
Any pins to be used by digital peripherals or as GPIO should be configured as digital I/O (PnMDIN.n = ‘1’). For
digital I/O pins, one of two output modes (push-pull or open-drain) must be selected using the PnMDOUT registers.
Push-pull outputs (PnMDOUT.n = ‘1’) drive the port pad to the supply rails based on the output logic value of the
port pin. Open-drain outputs have the high side driver disabled; therefore, they only drive the port pad to the lowside rail when the output logic value is ‘0’ and become high impedance inputs (both high low drivers turned off)
when the output logic value is ‘1’.
When a digital I/O cell is placed in the high impedance state, a weak pull-up transistor pulls the port pad to the highside rail to ensure the digital input is at a defined logic state. Weak pull-ups are disabled when the I/O cell is driven
low to minimize power consumption, and they may be globally disabled by setting WEAKPUD to ‘1’. The user
should ensure that digital I/O are always internally or externally pulled or driven to a valid logic state to minimize
power consumption. Port pins configured for digital I/O always read back the logic state of the port pad, regardless
of the output logic value of the port pin.
To configure a pin as digital input:
1. Set the bit associated with the pin in the PnMDIN register to ‘1’. This selects digital mode for the pin.
2. Clear the bit associated with the pin in the PnMDOUT register to ‘0’. This configures the pin as open-drain.
3. Set the bit associated with the pin in the Pn register to ‘1’. This tells the output driver to “drive” logic high.
Because the pin is configured as open-drain, the high-side driver is not active, and the pin may be used as
an input.
Open-drain outputs are configured exactly as digital inputs. However, the pin may be driven low by an assigned
peripheral, or by writing ‘0’ to the associated bit in the Pn register if the signal is a GPIO.
To configure a pin as a digital, push-pull output:
1. Set the bit associated with the pin in the PnMDIN register to ‘1’. This selects digital mode for the pin.
2. Set the bit associated with the pin in the PnMDOUT register to ‘1’. This configures the pin as push-pull.
If a digital pin is to be used as a general-purpose I/O, or with a digital function that is not part of the crossbar, the bit
associated with the pin in the PnSKIP register can be set to ‘1’ to ensure the crossbar does not attempt to assign a
function to the pin.
21.4.3. Port Drive Strength
Port drive strength can be controlled on a port-by-port basis using the PRTDRV register. Each port has a bit in
PRTDRV to select the high or low drive strength setting for all pins on that port. By default, all ports are configured
for high drive strength.
184
Preliminary Rev 0.6
WEAKPUD
(Weak Pull-Up Disable)
PxMDOUT.x
(1 for push-pull)
(0 for open-drain)
VDD
XBARE
(Crossbar
Enable)
VDD
(WEAK)
PORT
PAD
Px.x – Output
Logic Value
(Port Latch or
Crossbar)
PxMDIN.x
(1 for digital)
(0 for analog)
To/From Analog
Peripheral
GND
Px.x – Input Logic Value
(Reads 0 when pin is configured as an analog I/O)
Figure 21.4. Port I/O Cell Block Diagram
21.5. Port Match
Port match functionality allows system events to be triggered by a logic value change on one or more port I/O pins.
A software controlled value stored in the PnMATCH registers specifies the expected or normal logic values of the
associated port pins (for example, P0MATCH.0 would correspond to P0.0). A port mismatch event occurs if the
logic levels of the port’s input pins no longer match the software controlled value. This allows software to be notified
if a certain change or pattern occurs on the input pins regardless of the XBRn settings.
The PnMASK registers can be used to individually select which pins should be compared against the PnMATCH
registers. A port mismatch event is generated if (Pn & PnMASK) does not equal (PnMATCH & PnMASK) for all
ports with a PnMAT and PnMASK register.
A port mismatch event may be used to generate an interrupt or wake the device from idle mode. See the interrupts
and power options chapters for more details on interrupt and wake-up sources.
21.6. Direct Read/Write Access to Port I/O Pins
All port I/O are accessed through corresponding special function registers (SFRs) that are both byte addressable
and bit addressable. When writing to a port, the value written to the SFR is latched to 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 a
Port Latch register as the destination. The read-modify-write instructions when operating on a port SFR are the
following: ANL, ORL, XRL, JBC, CPL, INC, DEC, DJNZ and MOV, CLR or SETB, when the destination is an
individual bit in a port SFR. For these instructions, the value of the latch register (not the pin) is read, modified, and
written back to the SFR.
Preliminary Rev 0.6
185
Port I/O (Port 0, Port 1, Port 2, Crossbar, and Port Match)
C8051F85x/86x
Port I/O (Port 0, Port 1, Port 2, Crossbar, and Port Match)
C8051F85x/86x
21.7. Port I/O and Pin Configuration Control Registers
Register 21.1. XBR0: Port I/O Crossbar 0
Bit
7
6
5
4
3
2
1
0
Name
SYSCKE
CP1AE
CP1E
CP0AE
CP0E
SMB0E
SPI0E
URT0E
Type
RW
RW
RW
RW
RW
RW
RW
RW
Reset
0
0
0
0
0
0
0
0
SFR Address: 0xE1
Table 21.4. XBR0 Register Bit Descriptions
Bit
Name
7
SYSCKE
Function
SYSCLK Output Enable.
0: SYSCLK unavailable at Port pin.
1: SYSCLK output routed to Port pin.
6
CP1AE
Comparator1 Asynchronous Output Enable.
0: Asynchronous CP1 unavailable at Port pin.
1: Asynchronous CP1 routed to Port pin.
5
CP1E
Comparator1 Output Enable.
0: CP1 unavailable at Port pin.
1: CP1 routed to Port pin.
4
CP0AE
Comparator0 Asynchronous Output Enable.
0: Asynchronous CP0 unavailable at Port pin.
1: Asynchronous CP0 routed to Port pin.
3
CP0E
Comparator0 Output Enable.
0: CP0 unavailable at Port pin.
1: CP0 routed to Port pin.
2
SMB0E
SMBus0 I/O Enable.
0: SMBus0 I/O unavailable at Port pins.
1: SMBus0 I/O routed to Port pins.
1
SPI0E
SPI I/O Enable.
0: SPI I/O unavailable at Port pins.
1: SPI I/O routed to Port pins. The SPI can be assigned either 3 or 4 GPIO pins.
0
URT0E
UART I/O Output Enable.
0: UART I/O unavailable at Port pin.
1: UART TX, RX routed to Port pins P0.4 and P0.5.
186
Preliminary Rev 0.6
Register 21.2. XBR1: Port I/O Crossbar 1
Bit
7
Name
6
Reserved
5
4
3
2
T2E
T1E
T0E
ECIE
PCA0ME
RW
Type
R
RW
RW
RW
RW
RW
Reset
0
0
0
0
0
0
1
0
0
0
SFR Address: 0xE2
Table 21.5. XBR1 Register Bit Descriptions
Bit
Name
7:6
Reserved
5
T2E
Function
Must write reset value.
T2 Enable.
0: T2 unavailable at Port pin.
1: T2 routed to Port pin.
4
T1E
T1 Enable.
0: T1 unavailable at Port pin.
1: T1 routed to Port pin.
3
T0E
T0 Enable.
0: T0 unavailable at Port pin.
1: T0 routed to Port pin.
2
ECIE
PCA0 External Counter Input Enable.
0: ECI unavailable at Port pin.
1: ECI routed to Port pin.
1:0
PCA0ME
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.
Preliminary Rev 0.6
187
Port I/O (Port 0, Port 1, Port 2, Crossbar, and Port Match)
C8051F85x/86x
Port I/O (Port 0, Port 1, Port 2, Crossbar, and Port Match)
C8051F85x/86x
Register 21.3. XBR2: Port I/O Crossbar 2
Bit
7
6
5
4
Name
WEAKPUD
XBARE
Reserved
Type
RW
RW
R
Reset
0
0
0
3
0
0
2
1
0
0
0
0
SFR Address: 0xE3
Table 21.6. XBR2 Register Bit Descriptions
Bit
Name
7
WEAKPUD
Function
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.
5:0
188
Reserved
Must write reset value.
Preliminary Rev 0.6
Register 21.4. PRTDRV: Port Drive Strength
Bit
7
6
5
4
3
2
1
0
Name
Reserved
P2DRV
P1DRV
P0DRV
Type
R
RW
RW
RW
1
1
1
Reset
0
0
0
0
0
SFR Address: 0xF6
Table 21.7. PRTDRV Register Bit Descriptions
Bit
Name
Function
7:3
Reserved
Must write reset value.
2
P2DRV
Port 2 Drive Strength.
0: All pins on P2 use low drive strength.
1: All pins on P2 use high drive strength.
1
P1DRV
Port 1 Drive Strength.
0: All pins on P1 use low drive strength.
1: All pins on P1 use high drive strength.
0
P0DRV
Port 0 Drive Strength.
0: All pins on P0 use low drive strength.
1: All pins on P0 use high drive strength.
Preliminary Rev 0.6
189
Port I/O (Port 0, Port 1, Port 2, Crossbar, and Port Match)
C8051F85x/86x
Port I/O (Port 0, Port 1, Port 2, Crossbar, and Port Match)
C8051F85x/86x
Register 21.5. P0MASK: Port 0 Mask
Bit
7
6
5
4
Name
P0MASK
Type
RW
Reset
0
0
0
0
3
2
1
0
0
0
0
0
SFR Address: 0xFE
Table 21.8. P0MASK Register Bit Descriptions
Bit
Name
7:0
P0MASK
Function
Port 0 Mask Value.
Selects P0 pins to be compared to the corresponding bits in P0MAT.
0: P0.x pin logic value is ignored and will cause a port mismatch event.
1: P0.x pin logic value is compared to P0MAT.x.
190
Preliminary Rev 0.6
Register 21.6. P0MAT: Port 0 Match
Bit
7
6
5
4
Name
P0MAT
Type
RW
Reset
1
1
1
1
3
2
1
0
1
1
1
1
SFR Address: 0xFD
Table 21.9. P0MAT Register Bit Descriptions
Bit
Name
7:0
P0MAT
Function
Port 0 Match Value.
Match comparison value used on P0 pins for bits in P0MASK which are set to 1.
0: P0.x pin logic value is compared with logic LOW.
1: P0.x pin logic value is compared with logic HIGH.
Preliminary Rev 0.6
191
Port I/O (Port 0, Port 1, Port 2, Crossbar, and Port Match)
C8051F85x/86x
Port I/O (Port 0, Port 1, Port 2, Crossbar, and Port Match)
C8051F85x/86x
Register 21.7. P0: Port 0 Pin Latch
Bit
7
6
5
4
Name
P0
Type
RW
Reset
1
1
1
1
3
2
1
0
1
1
1
1
SFR Address: 0x80 (bit-addressable)
Table 21.10. P0 Register Bit Descriptions
Bit
Name
7:0
P0
Function
Port 0 Data.
Writing this register sets the port latch logic value for the associated I/O pins configured
as digital I/O.
Reading this register returns the logic value at the pin, regardless if it is configured as
output or input.
192
Preliminary Rev 0.6
Register 21.8. P0MDIN: Port 0 Input Mode
Bit
7
6
5
4
Name
P0MDIN
Type
RW
Reset
1
1
1
1
3
2
1
0
1
1
1
1
SFR Address: 0xF1
Table 21.11. P0MDIN Register Bit Descriptions
Bit
Name
7:0
P0MDIN
Function
Port 0 Input Mode.
Port pins configured for analog mode have their weak pullup, digital driver, and digital
receiver disabled.
0: Corresponding P0.x pin is configured for analog mode.
1: Corresponding P0.x pin is configured for digital mode.
Preliminary Rev 0.6
193
Port I/O (Port 0, Port 1, Port 2, Crossbar, and Port Match)
C8051F85x/86x
Port I/O (Port 0, Port 1, Port 2, Crossbar, and Port Match)
C8051F85x/86x
Register 21.9. P0MDOUT: Port 0 Output Mode
Bit
7
6
5
4
Name
P0MDOUT
Type
RW
Reset
0
0
0
0
3
2
1
0
0
0
0
0
SFR Address: 0xA4
Table 21.12. P0MDOUT Register Bit Descriptions
Bit
Name
7:0
P0MDOUT
Function
Port 0 Output Mode.
These bits are only applicable when the pin is configured for digital mode using the
P0MDIN register.
0: Corresponding P0.n Output is open-drain.
1: Corresponding P0.n Output is push-pull.
194
Preliminary Rev 0.6
Register 21.10. P0SKIP: Port 0 Skip
Bit
7
6
5
4
Name
P0SKIP
Type
RW
Reset
0
0
0
0
3
2
1
0
0
0
0
0
SFR Address: 0xD4
Table 21.13. P0SKIP Register Bit Descriptions
Bit
Name
7:0
P0SKIP
Function
Port 0 Skip.
These bits select port pins to be skipped by the crossbar decoder. Port pins used for analog, special functions or GPIO should be skipped.
0: Corresponding P0.x pin is not skipped by the crossbar.
1: Corresponding P0.x pin is skipped by the crossbar.
Preliminary Rev 0.6
195
Port I/O (Port 0, Port 1, Port 2, Crossbar, and Port Match)
C8051F85x/86x
Port I/O (Port 0, Port 1, Port 2, Crossbar, and Port Match)
C8051F85x/86x
Register 21.11. P1MASK: Port 1 Mask
Bit
7
6
5
4
Name
P1MASK
Type
RW
Reset
0
0
0
0
3
2
1
0
0
0
0
0
SFR Address: 0xEE
Table 21.14. P1MASK Register Bit Descriptions
Bit
Name
7:0
P1MASK
Function
Port 1 Mask Value.
Selects P1 pins to be compared to the corresponding bits in P1MAT.
0: P1.x pin logic value is ignored and will cause a port mismatch event.
1: P1.x pin logic value is compared to P1MAT.x.
Note: Port 1 consists of 8 bits (P1.0-P1.7) on QSOP24 packages and 7 bits (P1.0-P1.6) on QFN20 packages and 4 bits
(P1.0-P1.3) on SOIC16 packages.
196
Preliminary Rev 0.6
Register 21.12. P1MAT: Port 1 Match
Bit
7
6
5
4
Name
P1MAT
Type
RW
Reset
1
1
1
1
3
2
1
0
1
1
1
1
SFR Address: 0xED
Table 21.15. P1MAT Register Bit Descriptions
Bit
Name
7:0
P1MAT
Function
Port 1 Match Value.
Match comparison value used on P1 pins for bits in P1MASK which are set to 1.
0: P1.x pin logic value is compared with logic LOW.
1: P1.x pin logic value is compared with logic HIGH.
Note: Port 1 consists of 8 bits (P1.0-P1.7) on QSOP24 packages and 7 bits (P1.0-P1.6) on QFN20 packages and 4 bits
(P1.0-P1.3) on SOIC16 packages.
Preliminary Rev 0.6
197
Port I/O (Port 0, Port 1, Port 2, Crossbar, and Port Match)
C8051F85x/86x
Port I/O (Port 0, Port 1, Port 2, Crossbar, and Port Match)
C8051F85x/86x
Register 21.13. P1: Port 1 Pin Latch
Bit
7
6
5
4
Name
P1
Type
RW
Reset
1
1
1
1
3
2
1
0
1
1
1
1
SFR Address: 0x90 (bit-addressable)
Table 21.16. P1 Register Bit Descriptions
Bit
Name
7:0
P1
Function
Port 1 Data.
Writing this register sets the port latch logic value for the associated I/O pins configured
as digital I/O.
Reading this register returns the logic value at the pin, regardless if it is configured as
output or input.
Note: Port 1 consists of 8 bits (P1.0-P1.7) on QSOP24 packages and 7 bits (P1.0-P1.6) on QFN20 packages and 4 bits
(P1.0-P1.3) on SOIC16 packages.
198
Preliminary Rev 0.6
Register 21.14. P1MDIN: Port 1 Input Mode
Bit
7
6
5
4
Name
P1MDIN
Type
RW
Reset
1
1
1
1
3
2
1
0
1
1
1
1
SFR Address: 0xF2
Table 21.17. P1MDIN Register Bit Descriptions
Bit
Name
7:0
P1MDIN
Function
Port 1 Input Mode.
Port pins configured for analog mode have their weak pullup, digital driver, and digital
receiver disabled.
0: Corresponding P1.x pin is configured for analog mode.
1: Corresponding P1.x pin is configured for digital mode.
Note: Port 1 consists of 8 bits (P1.0-P1.7) on QSOP24 packages and 7 bits (P1.0-P1.6) on QFN20 packages and 4 bits
(P1.0-P1.3) on SOIC16 packages.
Preliminary Rev 0.6
199
Port I/O (Port 0, Port 1, Port 2, Crossbar, and Port Match)
C8051F85x/86x
Port I/O (Port 0, Port 1, Port 2, Crossbar, and Port Match)
C8051F85x/86x
Register 21.15. P1MDOUT: Port 1 Output Mode
Bit
7
6
5
4
Name
P1MDOUT
Type
RW
Reset
0
0
0
0
3
2
1
0
0
0
0
0
SFR Address: 0xA5
Table 21.18. P1MDOUT Register Bit Descriptions
Bit
Name
7:0
P1MDOUT
Function
Port 1 Output Mode.
These bits are only applicable when the pin is configured for digital mode using the
P1MDIN register.
0: Corresponding P1.n Output is open-drain.
1: Corresponding P1.n Output is push-pull.
Note: Port 1 consists of 8 bits (P1.0-P1.7) on QSOP24 packages and 7 bits (P1.0-P1.6) on QFN20 packages and 4 bits
(P1.0-P1.3) on SOIC16 packages.
200
Preliminary Rev 0.6
Register 21.16. P1SKIP: Port 1 Skip
Bit
7
6
5
4
Name
P1SKIP
Type
RW
Reset
0
0
0
0
3
2
1
0
0
0
0
0
SFR Address: 0xD5
Table 21.19. P1SKIP Register Bit Descriptions
Bit
Name
7:0
P1SKIP
Function
Port 1 Skip.
These bits select port pins to be skipped by the crossbar decoder. Port pins used for analog, special functions or GPIO should be skipped.
0: Corresponding P1.x pin is not skipped by the crossbar.
1: Corresponding P1.x pin is skipped by the crossbar.
Note: Port 1 consists of 8 bits (P1.0-P1.7) on QSOP24 packages and 7 bits (P1.0-P1.6) on QFN20 packages and 4 bits
(P1.0-P1.3) on SOIC16 packages.
Preliminary Rev 0.6
201
Port I/O (Port 0, Port 1, Port 2, Crossbar, and Port Match)
C8051F85x/86x
Port I/O (Port 0, Port 1, Port 2, Crossbar, and Port Match)
C8051F85x/86x
Register 21.17. P2: Port 2 Pin Latch
Bit
7
6
5
4
3
2
1
0
Name
Reserved
P2
Type
R
RW
Reset
0
0
0
0
0
0
1
1
SFR Address: 0xA0 (bit-addressable)
Table 21.20. P2 Register Bit Descriptions
Bit
Name
7:2
Reserved
1:0
P2
Function
Must write reset value.
Port 2 Data.
Writing this register sets the port latch logic value for the associated I/O pins configured
as digital I/O.
Reading this register returns the logic value at the pin, regardless if it is configured as
output or input.
Note: Port 2 consists of 2 bits (P2.0-P2.1) on QSOP24 devices and 1 bit (P2.0) on QFN20 and SOIC16 packages.
202
Preliminary Rev 0.6
Register 21.18. P2MDOUT: Port 2 Output Mode
Bit
7
6
5
4
3
2
1
0
Name
Reserved
P2MDOUT
Type
R
RW
Reset
0
0
0
0
0
0
0
0
SFR Address: 0xA6
Table 21.21. P2MDOUT Register Bit Descriptions
Bit
Name
Function
7:2
Reserved
Must write reset value.
1:0
P2MDOUT
Port 2 Output Mode.
0: Corresponding P2.n Output is open-drain.
1: Corresponding P2.n Output is push-pull.
Note: Port 2 consists of 2 bits (P2.0-P2.1) on QSOP24 devices and 1 bit (P2.0) on QFN20 and SOIC16 packages.
Preliminary Rev 0.6
203
Port I/O (Port 0, Port 1, Port 2, Crossbar, and Port Match)
C8051F85x/86x
Reset Sources and Supply Monitor
C8051F85x/86x
22. Reset Sources and Supply Monitor
Reset circuitry allows the controller to be easily placed in a predefined default condition. Upon entering this reset
state, the following events occur:
CIP-51
halts program execution
Function Registers (SFRs) are initialized to their defined reset values
External port pins are placed in a known state
Interrupts and timers are disabled.
All SFRs are reset to the predefined values noted in the SFR detailed descriptions. The contents of internal data
memory are unaffected during a reset; any previously stored data is preserved. However, since the stack pointer
SFR is reset, the stack is effectively lost, even though the data on the stack is not altered.
Special
The Port I/O latches are reset to 0xFF (all logic ones) in open-drain, low-drive 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
reset state. Note that during a power-on event, there may be a short delay before the POR circuitry fires and the
RST pin is driven low. During that time, the RST pin will be weakly pulled to the VDD supply pin.
On exit from the reset state, the program counter (PC) is reset, the Watchdog Timer is enabled and the system
clock defaults to the internal oscillator. Program execution begins at location 0x0000.
Reset Sources
RST
Supply Monitor or
Power-up
Missing Clock
Detector
Watchdog Timer
system reset
Software Reset
Comparator 0
Flash Error
Figure 22.1. Reset Sources
204
Preliminary Rev 0.6
22.1. Power-On Reset
During power-up, the POR circuit will fire. When POR fires, the device is held in a reset state and the RST pin is
driven low until VDD settles above VRST. Two delays are present during the supply ramp time. First, a delay will
occur before the POR circuitry fires and pulls the RST pin low. A second 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 22.2. plots the power-on reset timing. For ramp times less than 1 ms, the power-on reset
time (TPOR) is typically less than 0.3 ms. Additionally, the power supply must reach VRST before the POR circuit will
release the device from reset.
VD
D
volts
On exit from a power-on 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 content of internal data memory should be assumed to be
undefined after a power-on reset. The VDD monitor is enabled following a power-on reset.
t
Logic HIGH
Logic LOW
RST
TPOR
Power-On Reset
Figure 22.2. Power-on Reset Timing
Preliminary Rev 0.6
205
Reset Sources and Supply Monitor
C8051F85x/86x
22.2. Power-Fail Reset / Supply Monitor
C8051F85x/86x devices have a supply monitor that is enabled and selected as a reset source after each power-on.
The supply monitor senses the voltage on the device VDD supply and can generate a reset if the supply drops
below the corresponding threshold. This monitor is enabled and enabled as a reset source after initial power-on to
protect the device until VDD is an adequate and stable voltage.
When enabled and selected as a reset source, any power down transition or power irregularity that causes VDD to
drop below the reset threshold will drive the RST pin low and hold the core in a reset state. When VDD returns to a
level above the reset threshold, the monitor will release the core from the reset state. The reset status can then be
read using the device reset sources module. After a power-fail reset, the PORF flag reads 1 and all of the other
reset flags in the RSTSRC Register are indeterminate. The power-on reset delay (tPOR) is not incurred after a
supply monitor reset. The contents of RAM should be presumed invalid after a VDD monitor reset.
The enable state of the VDD supply monitor and its selection as a reset source is not altered by device resets. For
example, if the VDD supply monitor is de-selected as a reset source and disabled by software, and then firmware
performs a software reset, the VDD supply monitor will remain disabled and de-selected after the reset.
To protect the integrity of flash contents, the VDD supply monitor must be enabled and selected as a reset source
if software contains routines that erase or write flash memory. If the VDD supply monitor is not enabled, any erase
or write performed on flash memory will be ignored.
volts
Reset Sources and Supply Monitor
C8051F85x/86x
VDD
Reset Threshold
(VRST)
t
RST
VDD Monitor
Reset
Figure 22.3. VDD Supply Monitor Threshold
22.3. Enabling the VDD Monitor
The VDD supply monitor is enabled by default. However, in systems which disable the supply monitor, it must be
enabled before selecting it as a reset source. Selecting the VDD supply monitor as a reset source before it has
stabilized may generate a system reset. In systems where this reset would be undesirable, a delay should be
introduced between enabling the VDD supply monitor and selecting it as a reset source. No delay should be
introduced in systems where software contains routines that erase or write flash memory. The procedure for
enabling the VDD supply monitor and selecting it as a reset source is:
1. Enable the VDD supply monitor (VMONEN = 1).
2. Wait for the VDD supply monitor to stabilize (optional).
3. Enable the VDD monitor as a reset source in the RSTSRC register.
206
Preliminary Rev 0.6
22.4. External Reset
The external RST pin provides a means for external circuitry to force the device into a reset state. Asserting an
active-low signal on the RST pin generates a reset; an external pullup and/or decoupling of the RST pin may be
necessary to avoid erroneous noise-induced resets. The PINRSF flag is set on exit from an external reset.
22.5. Missing Clock Detector Reset
The Missing Clock Detector (MCD) is a one-shot circuit that is triggered by the system clock. If the system clock
remains high or low for more than the MCD time window, the one-shot will time out and generate a reset. After a
MCD reset, the MCDRSF flag will read 1, signifying the MCD as the reset source; otherwise, this bit reads 0.
Writing a 1 to the MCDRSF bit enables the Missing Clock Detector; writing a 0 disables it. The state of the RST pin
is unaffected by this reset.
22.6. Comparator0 Reset
Comparator0 can be configured as a reset source by writing a 1 to the C0RSEF flag. Comparator0 should be
enabled and allowed to settle prior to writing to C0RSEF to prevent any turn-on chatter on the output from
generating an unwanted reset. The Comparator0 reset is active-low: if the non-inverting input voltage (on CP0+) is
less than the inverting input voltage (on CP0-), the device is put into the reset state. After a Comparator0 reset, the
C0RSEF flag 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.
22.7. Watchdog Timer Reset
The programmable Watchdog Timer (WDT) can be used to prevent software from running out of control during a
system malfunction. The WDT function can be enabled or disabled by software as described in the watchdog timer
section. If a system malfunction prevents user software from updating the WDT, a reset is generated and the
WDTRSF bit is set to ‘1’. The state of the RST pin is unaffected by this reset.
22.8. Flash Error Reset
If a flash read/write/erase or program read targets an illegal address, a system reset is generated. This may occur
due to any of the following:
A
flash write or erase is attempted above user code space.
A flash read is attempted above user code space.
A program read is attempted above user code space (i.e. a branch instruction to the reserved area).
A flash read, write or erase attempt is restricted due to a flash security setting.
The FERROR bit is set following a flash error reset. The state of the RST pin is unaffected by this reset.
22.9. Software Reset
Software may force a reset by writing a 1 to the SWRSF bit. The SWRSF bit will read 1 following a software forced
reset. The state of the RST pin is unaffected by this reset.
Preliminary Rev 0.6
207
Reset Sources and Supply Monitor
C8051F85x/86x
Reset Sources and Supply Monitor
C8051F85x/86x
22.10. Reset Sources Control Registers
Register 22.1. SPI0CFG: SPI0 Configuration
Bit
7
6
5
4
3
2
1
0
Name
SPIBSY
MSTEN
CKPHA
CKPOL
SLVSEL
NSSIN
SRMT
RXBMT
Type
R
RW
RW
RW
R
R
R
R
Reset
0
0
0
0
0
1
1
1
SFR Address: 0xA1
Table 22.1. SPI0CFG Register Bit Descriptions
Bit
Name
7
SPIBSY
Function
SPI Busy.
This bit is set to logic 1 when a SPI transfer is in progress (master or slave mode).
6
MSTEN
Master Mode Enable.
0: Disable master mode. Operate in slave mode.
1: Enable master mode. Operate as a master.
5
CKPHA
SPI0 Clock Phase.
0: Data centered on first edge of SCK period.
1: Data centered on second edge of SCK period.
4
CKPOL
SPI0 Clock Polarity.
0: SCK line low in idle state.
1: SCK line high in idle state.
3
SLVSEL
Slave Selected Flag.
This bit is set to logic 1 whenever the NSS pin is low indicating SPI0 is the selected
slave. It is cleared to logic 0 when NSS is high (slave not selected). This bit does not indicate the instantaneous value at the NSS pin, but rather a de-glitched version of the pin
input.
2
NSSIN
NSS Instantaneous Pin Input.
This bit mimics the instantaneous value that is present on the NSS port pin at the time
that the register is read. This input is not de-glitched.
1
SRMT
Shift Register Empty (valid in slave mode only).
This bit will be set to logic 1 when all data has been transferred in/out of the shift register,
and there is no new information available to read from the transmit buffer or write to the
receive buffer. It returns to logic 0 when a data byte is transferred to the shift register
from the transmit buffer or by a transition on SCK. SRMT = 1 when in Master Mode.
0
RXBMT
Receive Buffer Empty (valid in slave mode only).
This bit will be set to logic 1 when the receive buffer has been read and contains no new
information. If there is new information available in the receive buffer that has not been
read, this bit will return to logic 0. RXBMT = 1 when in Master Mode.
Note: In slave mode, data on MOSI is sampled in the center of each data bit. In master mode, data on MISO is sampled one
SYSCLK before the end of each data bit, to provide maximum settling time for the slave device.
208
Preliminary Rev 0.6
Register 22.2. SPI0CN: SPI0 Control
Bit
7
6
5
4
Name
SPIF
WCOL
MODF
RXOVRN
Type
RW
RW
RW
RW
Reset
0
0
0
0
3
2
1
0
NSSMD
TXBMT
SPIEN
RW
R
RW
1
0
0
1
SFR Address: 0xF8 (bit-addressable)
Table 22.2. SPI0CN Register Bit Descriptions
Bit
Name
7
SPIF
Function
SPI0 Interrupt Flag.
This bit is set to logic 1 by hardware at the end of a data transfer. If SPI interrupts are
enabled, an interrupt will be generated. This bit is not automatically cleared by hardware,
and must be cleared by software.
6
WCOL
Write Collision Flag.
This bit is set to logic 1 if a write to SPI0DAT is attempted when TXBMT is 0. When this
occurs, the write to SPI0DAT will be ignored, and the transmit buffer will not be written. If
SPI interrupts are enabled, an interrupt will be generated. This bit is not automatically
cleared by hardware, and must be cleared by software.
5
MODF
Mode Fault Flag.
This bit is set to logic 1 by hardware when a master mode collision is detected (NSS is
low, MSTEN = 1, and NSSMD = 01). If SPI interrupts are enabled, an interrupt will be
generated. This bit is not automatically cleared by hardware, and must be cleared by
software.
4
RXOVRN
Receive Overrun Flag (valid in slave mode only).
This bit is set to logic 1 by hardware when the receive buffer still holds unread data from
a previous transfer and the last bit of the current transfer is shifted into the SPI0 shift register. If SPI interrupts are enabled, an interrupt will be generated. This bit is not automatically cleared by hardware, and must be cleared by software.
3:2
NSSMD
Slave Select Mode.
Selects between the following NSS operation modes:
00: 3-Wire Slave or 3-Wire Master Mode. NSS signal is not routed to a port pin.
01: 4-Wire Slave or Multi-Master Mode (Default). NSS is an input to the device.
10: 4-Wire Single-Master Mode. NSS is an output and logic low.
11: 4-Wire Single-Master Mode. NSS is an output and logic high.
1
TXBMT
Transmit Buffer Empty.
This bit will be set to logic 0 when new data has been written to the transmit buffer. When
data in the transmit buffer is transferred to the SPI shift register, this bit will be set to logic
1, indicating that it is safe to write a new byte to the transmit buffer.
0
SPIEN
SPI0 Enable.
0: SPI disabled.
1: SPI enabled.
Preliminary Rev 0.6
209
Reset Sources and Supply Monitor
C8051F85x/86x
Reset Sources and Supply Monitor
C8051F85x/86x
Register 22.3. SPI0CKR: SPI0 Clock Rate
Bit
7
6
5
4
Name
SPI0CKR
Type
RW
Reset
0
0
0
0
3
2
1
0
0
0
0
0
SFR Address: 0xA2
Table 22.3. SPI0CKR Register Bit Descriptions
Bit
Name
7:0
SPI0CKR
Function
SPI0 Clock Rate.
These bits determine the frequency of the SCK output when the SPI0 module is configured for master mode operation. The SCK clock frequency is a divided version of the
system clock, and is given in the following equation, where SYSCLK is the system clock
frequency and SPI0CKR is the 8-bit value held in the SPI0CKR register.
SYSCLK
f SCK = ----------------------------------------------2   SPI0CKR + 1 
for 0 <= SPI0CKR <= 255
210
Preliminary Rev 0.6
Register 22.4. SPI0DAT: SPI0 Data
Bit
7
6
5
4
Name
SPI0DAT
Type
RW
Reset
0
0
0
0
3
2
1
0
0
0
0
0
SFR Address: 0xA3
Table 22.4. SPI0DAT Register Bit Descriptions
Bit
Name
7:0
SPI0DAT
Function
SPI0 Transmit and Receive Data.
The SPI0DAT register is used to transmit and receive SPI0 data. Writing data to SPI0DAT places the data into the transmit buffer and initiates a transfer when in master mode.
A read of SPI0DAT returns the contents of the receive buffer.
Register 22.5. RSTSRC: Reset Source
Bit
7
6
5
4
3
2
1
0
Name
Reserved
FERROR
C0RSEF
SWRSF
WDTRSF
MCDRSF
PORSF
PINRSF
Type
R
R
RW
RW
R
RW
RW
R
Reset
0
X
X
X
X
X
X
X
SFR Address: 0xEF
Table 22.5. RSTSRC Register Bit Descriptions
Bit
Name
Function
7
Reserved
Must write reset value.
6
FERROR
Flash Error Reset Flag.
This read-only bit is set to 1 if a flash read/write/erase error caused the last reset.
5
C0RSEF
Comparator0 Reset Enable and Flag.
Read: This bit reads 1 if Comparator0 caused the last reset.
Write: Writing a 1 to this bit enables Comparator0 (active-low) as a reset source.
Notes:
1. Reads and writes of the RSTSRC register access different logic in the device. Reading the register always returns
status information to indicate the source of the most recent reset. Writing to the register activates certain options as
reset sources. It is recommended to not use any kind of read-modify-write operation on this register.
2. When the PORSF bit reads back 1 all other RSTSRC flags are indeterminate.
3. Writing 1 to the PORSF bit when the supply monitor is not enabled and stabilized may cause a system reset.
Preliminary Rev 0.6
211
Reset Sources and Supply Monitor
C8051F85x/86x
Reset Sources and Supply Monitor
C8051F85x/86x
Table 22.5. RSTSRC Register Bit Descriptions
Bit
Name
4
SWRSF
Function
Software Reset Force and Flag.
Read: This bit reads 1 if last reset was caused by a write to SWRSF.
Write: Writing a 1 to this bit forces a system reset.
3
WDTRSF
Watchdog Timer Reset Flag.
This read-only bit is set to 1 if a watchdog timer overflow caused the last reset.
2
MCDRSF
Missing Clock Detector Enable and Flag.
Read: This bit reads 1 if a missing clock detector timeout caused the last reset.
Write: Writing a 1 to this bit enables the missing clock detector. The MCD triggers a reset
if a missing clock condition is detected.
1
PORSF
Power-On / Supply Monitor Reset Flag, and Supply Monitor Reset Enable.
Read: This bit reads 1 anytime a power-on or supply monitor reset has occurred.
Write: Writing a 1 to this bit enables the supply monitor as a reset source.
0
PINRSF
HW Pin Reset Flag.
This read-only bit is set to 1 if the RST pin caused the last reset.
Notes:
1. Reads and writes of the RSTSRC register access different logic in the device. Reading the register always returns
status information to indicate the source of the most recent reset. Writing to the register activates certain options as
reset sources. It is recommended to not use any kind of read-modify-write operation on this register.
2. When the PORSF bit reads back 1 all other RSTSRC flags are indeterminate.
3. Writing 1 to the PORSF bit when the supply monitor is not enabled and stabilized may cause a system reset.
Supply Monitor Control Registers
Register 22.6. VDM0CN: Supply Monitor Control
Bit
7
6
5
4
Name
VDMEN
VDDSTAT
Reserved
Type
RW
R
R
Reset
X
X
X
3
X
X
2
1
0
X
X
X
SFR Address: 0xFF
Table 22.6. VDM0CN Register Bit Descriptions
Bit
Name
7
VDMEN
Function
Supply Monitor Enable.
This bit turns the supply monitor circuit on/off. The supply monitor cannot generate system resets until it is also selected as a reset source in register RSTSRC. Selecting the
supply monitor as a reset source before it has stabilized may generate a system reset. In
systems where this reset would be undesirable, a delay should be introduced between
enabling the supply monitor and selecting it as a reset source.
0: Supply Monitor Disabled.
1: Supply Monitor Enabled.
212
Preliminary Rev 0.6
Table 22.6. VDM0CN Register Bit Descriptions
Bit
Name
6
VDDSTAT
Function
Supply Status.
This bit indicates the current power supply status (supply monitor output).
0: VDD is at or below the supply monitor threshold.
1: VDD is above the supply monitor threshold.
5:0
Reserved
Must write reset value.
Preliminary Rev 0.6
213
Reset Sources and Supply Monitor
C8051F85x/86x
Serial Peripheral Interface (SPI0)
C8051F85x/86x
23. Serial Peripheral Interface (SPI0)
The serial peripheral interface (SPI0) provides access to a flexible, full-duplex synchronous serial bus. SPI0 can
operate as a master or slave device in both 3-wire or 4-wire modes, and supports multiple masters and slaves on a
single SPI bus. The slave-select (NSS) signal can be configured as an input to select SPI0 in slave mode, or to
disable Master Mode operation in a multi-master environment, avoiding contention on the SPI bus when more than
one master attempts simultaneous data transfers. NSS can also be configured as a chip-select output in master
mode, or disabled for 3-wire operation. Additional general purpose port I/O pins can be used to select multiple
slave devices in master mode.
SPI0
SYSCLK
Clock Rate
Generator
SCK Phase
Master or Slave
SCK Polarity
NSS Control
NSS
Bus Control
SCK
Shift Register
TX Buffer
RX Buffer
SPI0DAT
Figure 23.1. SPI0 Block Diagram
214
Preliminary Rev 0.6
MISO
MOSI
23.1. Signal Descriptions
The four signals used by SPI0 (MOSI, MISO, SCK, NSS) are described below.
23.1.1. Master Out, Slave In (MOSI)
The master-out, slave-in (MOSI) signal is an output from a master device and an input to slave devices. It is used
to serially transfer data from the master to the slave. This signal is an output when SPI0 is operating as a master
and an input when SPI0 is operating as a slave. Data is transferred most-significant bit first. When configured as a
master, MOSI is driven by the MSB of the shift register in both 3- and 4-wire mode.
23.1.2. Master In, Slave Out (MISO)
The master-in, slave-out (MISO) signal is an output from a slave device and an input to the master device. It is
used to serially transfer data from the slave to the master. This signal is an input when SPI0 is operating as a
master and an output when SPI0 is operating as a slave. Data is transferred most-significant bit first. The MISO pin
is placed in a high-impedance state when the SPI module is disabled and when the SPI operates in 4-wire mode as
a slave that is not selected. When acting as a slave in 3-wire mode, MISO is always driven by the MSB of the shift
register.
23.1.3. Serial Clock (SCK)
The serial clock (SCK) signal is an output from the master device and an input to slave devices. It is used to
synchronize the transfer of data between the master and slave on the MOSI and MISO lines. SPI0 generates this
signal when operating as a master. The SCK signal is ignored by a SPI slave when the slave is not selected
(NSS = 1) in 4-wire slave mode.
23.1.4. Slave Select (NSS)
The function of the slave-select (NSS) signal is dependent on the setting of the NSSMD1 and NSSMD0 bits in the
SPI0CN register. There are three possible modes that can be selected with these bits:
1. NSSMD[1:0] = 00: 3-Wire Master or 3-Wire Slave Mode: SPI0 operates in 3-wire mode, and NSS is
disabled. When operating as a slave device, SPI0 is always selected in 3-wire mode. Since no select signal
is present, SPI0 must be the only slave on the bus in 3-wire mode. This is intended for point-to-point
communication between a master and one slave.
2. NSSMD[1:0] = 01: 4-Wire Slave or Multi-Master Mode: SPI0 operates in 4-wire mode, and NSS is enabled
as an input. When operating as a slave, NSS selects the SPI0 device. When operating as a master, a 1-to0 transition of the NSS signal disables the master function of SPI0 so that multiple master devices can be
used on the same SPI bus.
3. NSSMD[1:0] = 1x: 4-Wire Master Mode: SPI0 operates in 4-wire mode, and NSS is enabled as an output.
The setting of NSSMD0 determines what logic level the NSS pin will output. This configuration should only
be used when operating SPI0 as a master device.
See Figure 23.2, Figure 23.3, and Figure 23.4 for typical connection diagrams of the various operational modes.
Note that the setting of NSSMD bits affects the pinout of the device. When in 3-wire master or 3-wire slave
mode, the NSS pin will not be mapped by the crossbar. In all other modes, the NSS signal will be mapped to a pin
on the device.
Preliminary Rev 0.6
215
Serial Peripheral Interface (SPI0)
C8051F85x/86x
Serial Peripheral Interface (SPI0)
C8051F85x/86x
23.2. SPI0 Master Mode Operation
A SPI master device initiates all data transfers on a SPI bus. SPI0 is placed in master mode by setting the Master
Enable flag (MSTEN, SPI0CN.6). Writing a byte of data to the SPI0 data register (SPI0DAT) when in master mode
writes to the transmit buffer. If the SPI shift register is empty, the byte in the transmit buffer is moved to the shift
register, and a data transfer begins. The SPI0 master immediately shifts out the data serially on the MOSI line while
providing the serial clock on SCK. The SPIF (SPI0CN.7) flag is set to logic 1 at the end of the transfer. If interrupts
are enabled, an interrupt request is generated when the SPIF flag is set. While the SPI0 master transfers data to a
slave on the MOSI line, the addressed SPI slave device simultaneously transfers the contents of its shift register to
the SPI master on the MISO line in a full-duplex operation. Therefore, the SPIF flag serves as both a transmitcomplete and receive-data-ready flag. The data byte received from the slave is transferred MSB-first into the
master's shift register. When a byte is fully shifted into the register, it is moved to the receive buffer where it can be
read by the processor by reading SPI0DAT.
When configured as a master, SPI0 can operate in one of three different modes: multi-master mode, 3-wire singlemaster mode, and 4-wire single-master mode. The default, multi-master mode is active when NSSMD1
(SPI0CN.3) = 0 and NSSMD0 (SPI0CN.2) = 1. In this mode, NSS is an input to the device, and is used to disable
the master SPI0 when another master is accessing the bus. When NSS is pulled low in this mode, MSTEN
(SPI0CN.6) and SPIEN (SPI0CN.0) are set to 0 to disable the SPI master device, and a Mode Fault is generated
(MODF, SPI0CN.5 = 1). Mode Fault will generate an interrupt if enabled. SPI0 must be manually re-enabled in
software under these circumstances. In multi-master systems, devices will typically default to being slave devices
while they are not acting as the system master device. In multi-master mode, slave devices can be addressed
individually (if needed) using general-purpose I/O pins. Figure 23.2 shows a connection diagram between two
master devices and a single slave in multiple-master mode.
3-wire single-master mode is active when NSSMD1 (SPI0CN.3) = 0 and NSSMD0 (SPI0CN.2) = 0. In this mode,
NSS is not used, and is not mapped to an external port pin through the crossbar. Any slave devices that must be
addressed in this mode should be selected using general-purpose I/O pins. Figure 23.3 shows a connection
diagram between a master device in 3-wire master mode and a slave device.
4-wire single-master mode is active when NSSMD1 (SPI0CN.3) = 1. In this mode, NSS is configured as an output
pin, and can be used as a slave-select signal for a single SPI device. In this mode, the output value of NSS is
controlled (in software) with the bit NSSMD0 (SPI0CN.2). Additional slave devices can be addressed using
general-purpose I/O pins. Figure 23.4 shows a connection diagram for a master device and a slave device in 4wire mode.
216
Preliminary Rev 0.6
Master Device 1
Slave Device
SCK
SCK
MISO
MISO
MOSI
MOSI
NSS
NSS
port pin
Master Device 2
NSS
MOSI
MISO
SCK
port pin
Figure 23.2. Multiple-Master Mode Connection Diagram
Master Device
Slave Device
SCK
SCK
MISO
MISO
MOSI
MOSI
Figure 23.3. 3-Wire Single Master and 3-Wire Single Slave Mode Connection Diagram
Master Device
Slave Device
SCK
SCK
MISO
MISO
MOSI
MOSI
NSS
NSS
Figure 23.4. 4-Wire Single Master Mode and 4-Wire Slave Mode Connection Diagram
Preliminary Rev 0.6
217
Serial Peripheral Interface (SPI0)
C8051F85x/86x
Serial Peripheral Interface (SPI0)
C8051F85x/86x
23.3. SPI0 Slave Mode Operation
When SPI0 is enabled and not configured as a master, it will operate as a SPI slave. As a slave, bytes are shifted
in through the MOSI pin and out through the MISO pin by a master device controlling the SCK signal. A bit counter
in the SPI0 logic counts SCK edges. When 8 bits have been shifted through the shift register, the SPIF flag is set to
logic 1, and the byte is copied into the receive buffer. Data is read from the receive buffer by reading SPI0DAT. A
slave device cannot initiate transfers. Data to be transferred to the master device is pre-loaded into the shift
register by writing to SPI0DAT. Writes to SPI0DAT are double-buffered, and are placed in the transmit buffer first. If
the shift register is empty, the contents of the transmit buffer will immediately be transferred into the shift register.
When the shift register already contains data, the SPI will load the shift register with the transmit buffer’s contents
after the last SCK edge of the next (or current) SPI transfer.
When configured as a slave, SPI0 can be configured for 4-wire or 3-wire operation. The default, 4-wire slave mode,
is active when NSSMD1 (SPI0CN.3) = 0 and NSSMD0 (SPI0CN.2) = 1. In 4-wire mode, the NSS signal is routed to
a port pin and configured as a digital input. SPI0 is enabled when NSS is logic 0, and disabled when NSS is logic 1.
The bit counter is reset on a falling edge of NSS. Note that the NSS signal must be driven low at least 2 system
clocks before the first active edge of SCK for each byte transfer. Figure 23.4 shows a connection diagram between
two slave devices in 4-wire slave mode and a master device.
The 3-wire slave mode is active when NSSMD1 (SPI0CN.3) = 0 and NSSMD0 (SPI0CN.2) = 0. NSS is not used in
this mode, and is not mapped to an external port pin through the crossbar. Since there is no way of uniquely
addressing the device in 3-wire slave mode, SPI0 must be the only slave device present on the bus. It is important
to note that in 3-wire slave mode there is no external means of resetting the bit counter that determines when a full
byte has been received. The bit counter can only be reset by disabling and re-enabling SPI0 with the SPIEN bit.
Figure 23.3 shows a connection diagram between a slave device in 3-wire slave mode and a master device.
23.4. SPI0 Interrupt Sources
When SPI0 interrupts are enabled, the following four flags will generate an interrupt when they are set to logic 1:
All of the following bits must be cleared by software.
The
SPI Interrupt Flag, SPIF (SPI0CN.7) is set to logic 1 at the end of each byte transfer. This flag can
occur in all SPI0 modes.
The Write Collision Flag, WCOL (SPI0CN.6) is set to logic 1 if a write to SPI0DAT is attempted when the
transmit buffer has not been emptied to the SPI shift register. When this occurs, the write to SPI0DAT will
be ignored, and the transmit buffer will not be written.This flag can occur in all SPI0 modes.
The Mode Fault Flag MODF (SPI0CN.5) is set to logic 1 when SPI0 is configured as a master, and for
multi-master mode and the NSS pin is pulled low. When a Mode Fault occurs, the MSTEN and SPIEN bits
in SPI0CN are set to logic 0 to disable SPI0 and allow another master device to access the bus.
The Receive Overrun Flag RXOVRN (SPI0CN.4) is set to logic 1 when configured as a slave, and a
transfer is completed and the receive buffer still holds an unread byte from a previous transfer. The new
byte is not transferred to the receive buffer, allowing the previously received data byte to be read. The data
byte which caused the overrun is lost.
23.5. Serial Clock Phase and Polarity
Four combinations of serial clock phase and polarity can be selected using the clock control bits in the SPI0
Configuration Register (SPI0CFG). The CKPHA bit (SPI0CFG.5) selects one of two clock phases (edge used to
latch the data). The CKPOL bit (SPI0CFG.4) selects between an active-high or active-low clock. Both master and
slave devices must be configured to use the same clock phase and polarity. SPI0 should be disabled (by clearing
the SPIEN bit, SPI0CN.0) when changing the clock phase or polarity. The clock and data line relationships for
master mode are shown in Figure 23.5. For slave mode, the clock and data relationships are shown in Figure 23.6
and Figure 23.7. Note that CKPHA should be set to 0 on both the master and slave SPI when communicating
between two Silicon Labs C8051 devices.
218
Preliminary Rev 0.6
The SPI0 Clock Rate Register (SPI0CKR) controls the master mode serial clock frequency. This register is ignored
when operating in slave mode. When the SPI is configured as a master, the maximum data transfer rate (bits/sec)
is one-half the system clock frequency or 12.5 MHz, whichever is slower. When the SPI is configured as a slave,
the maximum data transfer rate (bits/sec) for full-duplex operation is 1/10 the system clock frequency, provided that
the master issues SCK, NSS (in 4-wire slave mode), and the serial input data synchronously with the slave’s
system clock. If the master issues SCK, NSS, and the serial input data asynchronously, the maximum data transfer
rate (bits/sec) must be less than 1/10 the system clock frequency. In the special case where the master only wants
to transmit data to the slave and does not need to receive data from the slave (i.e. half-duplex operation), the SPI
slave can receive data at a maximum data transfer rate (bits/sec) of 1/4 the system clock frequency. This is
provided that the master issues SCK, NSS, and the serial input data synchronously with the slave’s system clock.
SCK
(CKPOL=0, CKPHA=0)
SCK
(CKPOL=0, CKPHA=1)
SCK
(CKPOL=1, CKPHA=0)
SCK
(CKPOL=1, CKPHA=1)
MISO/MOSI
MSB
Bit 6
Bit 5
Bit 4
Bit 3
Bit 2
Bit 1
Bit 0
NSS (Must Remain High
in Multi-Master Mode)
Figure 23.5. Master Mode Data/Clock Timing
SCK
(CKPOL=0, CKPHA=0)
SCK
(CKPOL=1, CKPHA=0)
MOSI
MSB
Bit 6
Bit 5
Bit 4
Bit 3
Bit 2
Bit 1
Bit 0
MISO
MSB
Bit 6
Bit 5
Bit 4
Bit 3
Bit 2
Bit 1
Bit 0
NSS (4-Wire Mode)
Figure 23.6. Slave Mode Data/Clock Timing (CKPHA = 0)
Preliminary Rev 0.6
219
Serial Peripheral Interface (SPI0)
C8051F85x/86x
Serial Peripheral Interface (SPI0)
C8051F85x/86x
SCK
(CKPOL=0, CKPHA=1)
SCK
(CKPOL=1, CKPHA=1)
MOSI
MSB
Bit 6
Bit 5
Bit 4
Bit 3
Bit 2
Bit 1
MISO
MSB
Bit 6
Bit 5
Bit 4
Bit 3
Bit 2
Bit 1
Bit 0
Bit 0
NSS (4-Wire Mode)
Figure 23.7. Slave Mode Data/Clock Timing (CKPHA = 1)
23.6. SPI Special Function Registers
SPI0 is accessed and controlled through four special function registers in the system controller: SPI0CN Control
Register, SPI0DAT Data Register, SPI0CFG Configuration Register, and SPI0CKR Clock Rate Register. The four
special function registers related to the operation of the SPI0 Bus are described in the following figures.
SCK*
T
MCKH
T
MCKL
T
MIS
T
MIH
MISO
MOSI
* SCK is shown for CKPOL = 0. SCK is the opposite polarity for CKPOL = 1.
Figure 23.8. SPI Master Timing (CKPHA = 0)
220
Preliminary Rev 0.6
SCK*
T
T
MCKH
MCKL
T
T
MIS
MIH
MISO
MOSI
* SCK is shown for CKPOL = 0. SCK is the opposite polarity for CKPOL = 1.
Figure 23.9. SPI Master Timing (CKPHA = 1)
NSS
T
T
SE
T
CKL
SD
SCK*
T
CKH
T
SIS
T
SIH
MOSI
T
SEZ
T
T
SOH
SDZ
MISO
* SCK is shown for CKPOL = 0. SCK is the opposite polarity for CKPOL = 1.
Figure 23.10. SPI Slave Timing (CKPHA = 0)
Preliminary Rev 0.6
221
Serial Peripheral Interface (SPI0)
C8051F85x/86x
Serial Peripheral Interface (SPI0)
C8051F85x/86x
NSS
T
T
SE
T
CKL
SD
SCK*
T
CKH
T
SIS
T
SIH
MOSI
T
SEZ
T
T
SOH
SLH
MISO
* SCK is shown for CKPOL = 0. SCK is the opposite polarity for CKPOL = 1.
Figure 23.11. SPI Slave Timing (CKPHA = 1)
222
Preliminary Rev 0.6
T
SDZ
Table 23.1. SPI Slave Timing Parameters
Parameter
Description
Min
Max
Units
Master Mode Timing (See Figure 23.8 and Figure 23.9)
TMCKH
SCK High Time
1 x TSYSCLK
—
ns
TMCKL
SCK Low Time
1 x TSYSCLK
—
ns
TMIS
MISO Valid to SCK Shift Edge
1 x TSYSCLK + 20
—
ns
TMIH
SCK Shift Edge to MISO Change
0
—
ns
Slave Mode Timing (See Figure 23.10 and Figure 23.11)
TSE
NSS Falling to First SCK Edge
2 x TSYSCLK
—
ns
TSD
Last SCK Edge to NSS Rising
2 x TSYSCLK
—
ns
TSEZ
NSS Falling to MISO Valid
—
4 x TSYSCLK
ns
TSDZ
NSS Rising to MISO High-Z
—
4 x TSYSCLK
ns
TCKH
SCK High Time
5 x TSYSCLK
—
ns
TCKL
SCK Low Time
5 x TSYSCLK
—
ns
TSIS
MOSI Valid to SCK Sample Edge
2 x TSYSCLK
—
ns
TSIH
SCK Sample Edge to MOSI Change
2 x TSYSCLK
—
ns
TSOH
SCK Shift Edge to MISO Change
—
4 x TSYSCLK
ns
TSLH
Last SCK Edge to MISO Change 
(CKPHA = 1 ONLY)
6 x TSYSCLK
8 x TSYSCLK
ns
Note: TSYSCLK is equal to one period of the device system clock (SYSCLK).
Preliminary Rev 0.6
223
Serial Peripheral Interface (SPI0)
C8051F85x/86x
Serial Peripheral Interface (SPI0)
C8051F85x/86x
23.7. SPI Control Registers
Register 23.1. SPI0CFG: SPI0 Configuration
Bit
7
6
5
4
3
2
1
0
Name
SPIBSY
MSTEN
CKPHA
CKPOL
SLVSEL
NSSIN
SRMT
RXBMT
Type
R
RW
RW
RW
R
R
R
R
Reset
0
0
0
0
0
1
1
1
SFR Address: 0xA1
Table 23.2. SPI0CFG Register Bit Descriptions
Bit
Name
7
SPIBSY
Function
SPI Busy.
This bit is set to logic 1 when a SPI transfer is in progress (master or slave mode).
6
MSTEN
Master Mode Enable.
0: Disable master mode. Operate in slave mode.
1: Enable master mode. Operate as a master.
5
CKPHA
SPI0 Clock Phase.
0: Data centered on first edge of SCK period.
1: Data centered on second edge of SCK period.
4
CKPOL
SPI0 Clock Polarity.
0: SCK line low in idle state.
1: SCK line high in idle state.
3
SLVSEL
Slave Selected Flag.
This bit is set to logic 1 whenever the NSS pin is low indicating SPI0 is the selected
slave. It is cleared to logic 0 when NSS is high (slave not selected). This bit does not indicate the instantaneous value at the NSS pin, but rather a de-glitched version of the pin
input.
2
NSSIN
NSS Instantaneous Pin Input.
This bit mimics the instantaneous value that is present on the NSS port pin at the time
that the register is read. This input is not de-glitched.
1
SRMT
Shift Register Empty (valid in slave mode only).
This bit will be set to logic 1 when all data has been transferred in/out of the shift register,
and there is no new information available to read from the transmit buffer or write to the
receive buffer. It returns to logic 0 when a data byte is transferred to the shift register
from the transmit buffer or by a transition on SCK. SRMT = 1 when in Master Mode.
0
RXBMT
Receive Buffer Empty (valid in slave mode only).
This bit will be set to logic 1 when the receive buffer has been read and contains no new
information. If there is new information available in the receive buffer that has not been
read, this bit will return to logic 0. RXBMT = 1 when in Master Mode.
Note: In slave mode, data on MOSI is sampled in the center of each data bit. In master mode, data on MISO is sampled one
SYSCLK before the end of each data bit, to provide maximum settling time for the slave device.
224
Preliminary Rev 0.6
Register 23.2. SPI0CN: SPI0 Control
Bit
7
6
5
4
Name
SPIF
WCOL
MODF
RXOVRN
Type
RW
RW
RW
RW
Reset
0
0
0
0
3
2
1
0
NSSMD
TXBMT
SPIEN
RW
R
RW
1
0
0
1
SFR Address: 0xF8 (bit-addressable)
Table 23.3. SPI0CN Register Bit Descriptions
Bit
Name
7
SPIF
Function
SPI0 Interrupt Flag.
This bit is set to logic 1 by hardware at the end of a data transfer. If SPI interrupts are
enabled, an interrupt will be generated. This bit is not automatically cleared by hardware,
and must be cleared by software.
6
WCOL
Write Collision Flag.
This bit is set to logic 1 if a write to SPI0DAT is attempted when TXBMT is 0. When this
occurs, the write to SPI0DAT will be ignored, and the transmit buffer will not be written. If
SPI interrupts are enabled, an interrupt will be generated. This bit is not automatically
cleared by hardware, and must be cleared by software.
5
MODF
Mode Fault Flag.
This bit is set to logic 1 by hardware when a master mode collision is detected (NSS is
low, MSTEN = 1, and NSSMD = 01). If SPI interrupts are enabled, an interrupt will be
generated. This bit is not automatically cleared by hardware, and must be cleared by
software.
4
RXOVRN
Receive Overrun Flag (valid in slave mode only).
This bit is set to logic 1 by hardware when the receive buffer still holds unread data from
a previous transfer and the last bit of the current transfer is shifted into the SPI0 shift register. If SPI interrupts are enabled, an interrupt will be generated. This bit is not automatically cleared by hardware, and must be cleared by software.
3:2
NSSMD
Slave Select Mode.
Selects between the following NSS operation modes:
00: 3-Wire Slave or 3-Wire Master Mode. NSS signal is not routed to a port pin.
01: 4-Wire Slave or Multi-Master Mode (Default). NSS is an input to the device.
10: 4-Wire Single-Master Mode. NSS is an output and logic low.
11: 4-Wire Single-Master Mode. NSS is an output and logic high.
1
TXBMT
Transmit Buffer Empty.
This bit will be set to logic 0 when new data has been written to the transmit buffer. When
data in the transmit buffer is transferred to the SPI shift register, this bit will be set to logic
1, indicating that it is safe to write a new byte to the transmit buffer.
0
SPIEN
SPI0 Enable.
0: SPI disabled.
1: SPI enabled.
Preliminary Rev 0.6
225
Serial Peripheral Interface (SPI0)
C8051F85x/86x
Serial Peripheral Interface (SPI0)
C8051F85x/86x
Register 23.3. SPI0CKR: SPI0 Clock Rate
Bit
7
6
5
4
Name
SPI0CKR
Type
RW
Reset
0
0
0
0
3
2
1
0
0
0
0
0
SFR Address: 0xA2
Table 23.4. SPI0CKR Register Bit Descriptions
Bit
Name
7:0
SPI0CKR
Function
SPI0 Clock Rate.
These bits determine the frequency of the SCK output when the SPI0 module is configured for master mode operation. The SCK clock frequency is a divided version of the
system clock, and is given in the following equation, where SYSCLK is the system clock
frequency and SPI0CKR is the 8-bit value held in the SPI0CKR register.
SYSCLK
f SCK = ----------------------------------------------2   SPI0CKR + 1 
for 0 <= SPI0CKR <= 255
226
Preliminary Rev 0.6
Register 23.4. SPI0DAT: SPI0 Data
Bit
7
6
5
4
Name
SPI0DAT
Type
RW
Reset
0
0
0
0
3
2
1
0
0
0
0
0
SFR Address: 0xA3
Table 23.5. SPI0DAT Register Bit Descriptions
Bit
Name
7:0
SPI0DAT
Function
SPI0 Transmit and Receive Data.
The SPI0DAT register is used to transmit and receive SPI0 data. Writing data to SPI0DAT places the data into the transmit buffer and initiates a transfer when in master mode.
A read of SPI0DAT returns the contents of the receive buffer.
Preliminary Rev 0.6
227
Serial Peripheral Interface (SPI0)
C8051F85x/86x
24. System Management Bus / I2C (SMBus0)
The SMBus I/O interface is a two-wire, bi-directional serial bus. The SMBus is compliant with the System
Management Bus Specification, version 1.1, and compatible with the I2C serial bus.
Reads and writes to the SMBus 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, depending on the system clock used). A method
of extending the clock-low duration is available to accommodate devices with different speed capabilities on the
same bus.
The SMBus may operate as a master and/or slave, and may function on a bus with multiple masters. The SMBus
provides control of SDA (serial data), SCL (serial clock) generation and synchronization, arbitration logic, and
START/STOP control and generation. The SMBus peripherals can be fully driven by software (i.e., software
accepts/rejects slave addresses, and generates ACKs), or hardware slave address recognition and automatic ACK
generation can be enabled to minimize software overhead. A block diagram of the SMBus0 peripheral is shown in
Figure 24.1.
SMBus0
Data /
Address
SI
SMB0DAT
Shift Register
SDA
State Control
Logic
Slave Address
Recognition
SCL
Timers 0,
1 or 2
Master SCL Clock
Generation
Timer 3
SCL Low
Figure 24.1. SMBus0 Block Diagram
Preliminary Rev 0.6
229
System Management Bus / I2C (SMBus0)
C8051F85x/86x
System Management Bus / I2C (SMBus0)
C8051F85x/86x
24.1. Supporting Documents
It is assumed the reader is familiar with or has access to the following supporting documents:
1. The I2C-Bus and How to Use It (including specifications), Philips Semiconductor.
2. The I2C-Bus Specification—Version 2.0, Philips Semiconductor.
3. System Management Bus Specification—Version 1.1, SBS Implementers Forum.
24.2. SMBus Configuration
Figure 24.2 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 different voltage levels. However, the maximum
voltage on any port pin must conform to the electrical characteristics specifications. The bi-directional SCL (serial
clock) and SDA (serial data) lines must be connected to a positive power supply voltage through a pullup resistor or
similar circuit. Every device connected to the bus must have an open-drain or open-collector output for both the
SCL and SDA lines, so that both are pulled high (recessive state) when the bus is free. The maximum number of
devices on the bus is limited only by the requirement that the rise and fall times on the bus not exceed 300 ns and
1000 ns, respectively.
VDD = 5V
VDD = 3V
VDD = 5V
VDD = 3V
Master
Device
Slave
Device 1
Slave
Device 2
SDA
SCL
Figure 24.2. Typical SMBus Configuration
24.3. SMBus Operation
Two types of data transfers are possible: data transfers from a master transmitter to an addressed slave receiver
(WRITE), and data transfers from an addressed slave transmitter to a master receiver (READ). The master device
initiates both types of data transfers and provides the serial clock pulses on SCL. The SMBus interface may
operate as a master or a slave, and multiple master devices on the same bus are supported. If two or more
masters attempt to initiate a data transfer simultaneously, an arbitration scheme is employed with a single master
always winning the arbitration. It is not necessary to specify one device as the Master in a system; any device who
transmits a START and a slave address becomes the master for the duration of that transfer.
A typical SMBus transaction consists of a START condition followed by an address byte (Bits7–1: 7-bit slave
address; Bit0: R/W direction bit), one or more bytes of data, and a STOP condition. Bytes that are received (by a
master or slave) are acknowledged (ACK) with a low SDA during a high SCL (see Figure 24.3). If the receiving
device does not ACK, the transmitting device will read a NACK (not acknowledge), which is a high SDA during a
high SCL.
The direction bit (R/W) occupies the least-significant bit position of the address byte. The direction bit is set to logic
1 to indicate a "READ" operation and cleared to logic 0 to indicate a "WRITE" operation.
230
Preliminary Rev 0.6
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 transaction is a
WRITE operation from the master to the slave, the master transmits the data a byte at a time waiting for an ACK
from the slave at the end of each byte. For READ operations, the slave transmits the data waiting for an ACK from
the master at the end of each byte. At the end of the data transfer, the master generates a STOP condition to
terminate the transaction and free the bus. Figure 24.3 illustrates a typical SMBus transaction.
SCL
SDA
SLA6
START
SLA5-0
Slave Address + R/W
R/W
D7
ACK
D6-0
Data Byte
NACK
STOP
Figure 24.3. SMBus Transaction
24.3.1. Transmitter vs. Receiver
On the SMBus communications interface, a device is the “transmitter” when it is sending an address or data byte to
another device on the bus. A device is a “receiver” when an address or data byte is being sent to it from another
device on the bus. The transmitter controls the SDA line during the address or data byte. After each byte of
address or data information is sent by the transmitter, the receiver sends an ACK or NACK bit during the ACK
phase of the transfer, during which time the receiver controls the SDA line.
24.3.2. Arbitration
A master may start a transfer only if the bus is free. The bus is free after a STOP condition or after the SCL and
SDA lines remain high for a specified time (see Section “24.3.5. SCL High (SMBus Free) Timeout” on page 232). In
the event that two or more devices attempt to begin a transfer at the same time, an arbitration scheme is employed
to force one master to give up the bus. The master devices continue transmitting until one attempts a HIGH while
the other transmits a LOW. Since the bus is open-drain, the bus will be pulled LOW. The master attempting the
HIGH will detect a LOW SDA and lose the arbitration. The winning master continues its transmission without
interruption; the losing master becomes a slave and receives the rest of the transfer if addressed. This arbitration
scheme is non-destructive: one device always wins, and no data is lost.
24.3.3. 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.
24.3.4. SCL Low Timeout
If the SCL line is held low by a slave device on the bus, no further communication is possible. Furthermore, the
master cannot force the SCL line high to correct the error condition. To solve this problem, the SMBus protocol
specifies that devices participating in a transfer must detect any clock cycle held low longer than 25 ms as a
“timeout” condition. Devices that have detected the timeout condition must reset the communication no later than
10 ms after detecting the timeout condition.
For the SMBus0 interface, Timer 3 is used to implement SCL low timeouts. The SCL low timeout feature is enabled
by setting the SMB0TOE bit in SMB0CF. The associated timer is forced to reload when SCL is high, and allowed to
count when SCL is low. With the associated timer enabled and configured to overflow after 25 ms (and SMB0TOE
set), the timer interrupt service routine can be used to reset (disable and re-enable) the SMBus in the event of an
SCL low timeout.
Preliminary Rev 0.6
231
System Management Bus / I2C (SMBus0)
C8051F85x/86x
System Management Bus / I2C (SMBus0)
C8051F85x/86x
24.3.5. SCL High (SMBus Free) Timeout
The SMBus specification stipulates that if the SCL and SDA lines remain high for more that 50 µs, the bus is
designated as free. When the SMB0FTE 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 implementation.
24.4. Using the SMBus
The SMBus can operate in both Master and Slave modes. The interface provides timing and shifting control 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
signal generation on SCL (Master Mode only) and SDA data synchronization
Timeout/bus error recognition, as defined by the SMB0CF configuration register
START/STOP timing, detection, and generation
Bus arbitration
Interrupt generation
Status information
Optional hardware recognition of slave address and automatic acknowledgement of address/data
Clock
SMBus interrupts are generated for each data byte or slave address that is transferred. When hardware
acknowledgement is disabled, the point at which the interrupt is generated depends on whether the hardware is
acting as a data transmitter or receiver. When a transmitter (i.e., sending address/data, receiving an ACK), this
interrupt is generated after the ACK cycle so that software may read the received ACK value; when receiving data
(i.e., receiving address/data, sending an ACK), this interrupt is generated before the ACK cycle so that software
may define the outgoing ACK value. If hardware acknowledgement is enabled, these interrupts are always
generated after the ACK cycle. See Section 24.5 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. Table 24.5 provides a quick SMB0CN decoding reference.
24.4.1. SMBus Configuration Register
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 transfer).
Table 24.1. SMBus Clock Source Selection
232
SMBCS
SMBus0 Clock Source
00
Timer 0 Overflow
01
Timer 1 Overflow
10
Timer 2 High Byte Overflow
11
Timer 2 Low Byte Overflow
Preliminary Rev 0.6
The SMBCS bit field selects the SMBus clock source, which is used only when operating as a master or when the
Free Timeout detection is enabled. When operating as a master, overflows from the selected source determine the
absolute minimum SCL low and high times as defined in Equation 24.1.The selected clock source may be shared
by other peripherals so long as the timer is left running at all times.
1
T HighMin = T LowMin = ---------------------------------------------f ClockSourceOverflow
Equation 24.1. 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 24.1. 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 24.2.
f ClockSourceOverflow
BitRate = ---------------------------------------------3
Equation 24.2. Typical SMBus Bit Rate
Figure 24.4 shows the typical SCL generation described by Equation 24.2. 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 Equation 24.1.
Timer Source
Overflows
SCL
TLow
SCL High Timeout
THigh
Figure 24.4. Typical SMBus SCL Generation
Setting the EXTHOLD bit extends the minimum setup and hold times for the SDA line. The minimum SDA setup
time defines the absolute minimum time that SDA is stable before SCL transitions from low-to-high. The minimum
SDA hold time defines the absolute minimum time that the current SDA value remains stable after SCL transitions
from high-to-low. EXTHOLD should be set so that the minimum setup and hold times meet the SMBus
Specification requirements of 250 ns and 300 ns, respectively. Table 24.2 shows the minimum setup and hold
times for the two EXTHOLD settings. Setup and hold time extensions are typically necessary for SMBus
compliance when SYSCLK is above 10 MHz.
Table 24.2. Minimum SDA Setup and Hold Times
EXTHOLD
Minimum SDA Setup Time
Minimum SDA Hold Time
0
Tlow – 4 system clocks
or
1 system clock + s/w delay*
3 system clocks
1
11 system clocks
12 system clocks
Preliminary Rev 0.6
233
System Management Bus / I2C (SMBus0)
C8051F85x/86x
System Management Bus / I2C (SMBus0)
C8051F85x/86x
Table 24.2. Minimum SDA Setup and Hold Times
EXTHOLD
Minimum SDA Setup Time
Minimum SDA Hold Time
Note: Setup Time for ACK bit transmissions and the MSB of all data transfers. When using software acknowledgment, the s/
w delay occurs between the time SMB0DAT or ACK is written and when SI0 is cleared. Note that if SI is cleared in the
same write that defines the outgoing ACK value, s/w delay is zero.
With the SMBTOE bit set, Timer 3 should be configured to overflow after 25 ms in order to detect SCL low timeouts
(see Section “24.3.4. SCL Low Timeout” on page 231). The SMBus interface will force the associated timer to
reload while SCL is high, and allow the timer to count when SCL is low. The timer interrupt service routine should
be used to reset SMBus communication by disabling and re-enabling the SMBus.
SMBus Free Timeout detection can be enabled by setting the 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 24.4).
24.4.2. SMBus Pin Swap
The SMBus peripheral is assigned to pins using the priority crossbar decoder. By default, the SMBus signals are
assigned to port pins starting with SDA on the lower-numbered pin, and SCL on the next available pin. The SWAP
bit in the SMBTC register can be set to 1 to reverse the order in which the SMBus signals are assigned.
24.4.3. SMBus Timing Control
The SDD field in the SMBTC register is used to restrict the detection of a START condition under certain
circumstances. In some systems where there is significant mis-match between the impedance or the capacitance
on the SDA and SCL lines, it may be possible for SCL to fall after SDA during an address or data transfer. Such an
event can cause a false START detection on the bus. These kind of events are not expected in a standard SMBus
or I2C-compliant system. In most systems this parameter should not be adjusted, and it is recommended
that it be left at its default value.
By default, if the SCL falling edge is detected after the falling edge of SDA (i.e. one SYSCLK cycle or more), the
device will detect this as a START condition. The SDD field is used to increase the amount of hold time that is
required between SDA and SCL falling before a START is recognized. An additional 2, 4, or 8 SYSCLKs can be
added to prevent false START detection in systems where the bus conditions warrant this.
24.4.4. SMB0CN Control Register
SMB0CN is used to control the interface and to provide status information. 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 generate START and STOP conditions when operating as a master. Writing a 1 to
STA will cause the SMBus interface to enter Master Mode and generate a START when the bus becomes free
(STA is not cleared by hardware after the START is generated). Writing a 1 to STO while in Master Mode will cause
the interface to generate a STOP and end the current transfer after the next ACK cycle. If STO and STA are both
set (while in Master Mode), a STOP followed by a START will be generated.
The ARBLOST bit indicates that the interface has lost an arbitration. This may occur anytime the interface is
transmitting (master or slave). A lost arbitration while operating as a slave indicates a bus error condition.
ARBLOST is cleared by hardware each time SI is cleared.
The SI bit (SMBus Interrupt Flag) is set at the beginning and end of each transfer, after each byte frame, or when
an arbitration is lost; see Table 24.3 for more details.
Important Note About the SI Bit: The SMBus interface is stalled while SI is set; thus SCL is held low, and the bus
is stalled until software clears SI.
234
Preliminary Rev 0.6
24.4.4.1. Software ACK Generation
When the EHACK bit in register SMB0ADM is cleared to 0, the firmware on the device must detect incoming slave
addresses and ACK or NACK the slave address and incoming data bytes. As a receiver, writing the ACK bit defines
the outgoing ACK value; as a transmitter, reading the ACK bit indicates the value received during the last ACK
cycle. ACKRQ is set each time a byte is received, indicating that an outgoing ACK value is needed. When ACKRQ
is set, software should write the desired outgoing value to the ACK bit before clearing SI. A NACK will be generated
if software does not write the ACK bit before clearing SI. SDA will reflect the defined ACK value immediately
following a write to the ACK bit; however SCL will remain low until SI is cleared. If a received slave address is not
acknowledged, further slave events will be ignored until the next START is detected.
24.4.4.2. Hardware ACK Generation
When the EHACK bit in register SMB0ADM is set to 1, automatic slave address recognition and ACK generation is
enabled. More detail about automatic slave address recognition can be found in Section 24.4.5. As a receiver, the
value currently specified by the ACK bit will be automatically sent on the bus during the ACK cycle of an incoming
data byte. As a transmitter, reading the ACK bit indicates the value received on the last ACK cycle. The ACKRQ bit
is not used when hardware ACK generation is enabled. If a received slave address is NACKed by hardware,
further slave events will be ignored until the next START is detected, and no interrupt will be generated.
Table 24.3 lists all sources for hardware changes to the SMB0CN bits. Refer to Table 24.5 for SMBus status
decoding using the SMB0CN register.
Table 24.3. Sources for Hardware Changes to SMB0CN
Bit
MASTER
Set by Hardware When:
A
START is generated.
START
TXMODE
STA
STO
ACKRQ
ARBLOST
ACK
is generated.
SMB0DAT is written before the start of an
SMBus frame.
A
START followed by an address byte is
received.
A STOP is detected while addressed as a
slave.
Arbitration is lost due to a detected STOP.
A byte has been received and an ACK
response value is needed (only when
hardware ACK is not enabled).
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).
The incoming ACK value is low 
(ACKNOWLEDGE).
Preliminary Rev 0.6
Cleared by Hardware When:
A
STOP is generated.
is lost.
A START is detected.
Arbitration is lost.
SMB0DAT is not written before the
start of an SMBus frame.
Must be cleared by software.
Arbitration
A
pending STOP is generated.
After
each ACK cycle.
Each
time SIn is cleared.
The
incoming ACK value is high
(NOT ACKNOWLEDGE).
235
System Management Bus / I2C (SMBus0)
C8051F85x/86x
System Management Bus / I2C (SMBus0)
C8051F85x/86x
Table 24.3. Sources for Hardware Changes to SMB0CN
Bit
Set by Hardware When:
Cleared by Hardware When:
A
SI
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.
24.4.5. Hardware Slave Address Recognition
The SMBus hardware has the capability to automatically recognize incoming slave addresses and send an ACK
without software intervention. Automatic slave address recognition is enabled by setting the EHACK bit in register
SMB0ADM to 1. This will enable both automatic slave address recognition and automatic hardware ACK
generation for received bytes (as a master or slave). More detail on automatic hardware ACK generation can be
found in Section 24.4.4.2.
The registers used to define which address(es) are recognized by the hardware are the SMBus Slave Address
register and the SMBus Slave Address Mask register. A single address or range of addresses (including the
General Call Address 0x00) can be specified using these two registers. The most-significant seven bits of the two
registers are used to define which addresses will be ACKed. A 1 in a bit of the slave address mask SLVM enables
a comparison between the received slave address and the hardware’s slave address SLV for that bit. A 0 in a bit of
the slave address mask means that bit will be treated as a “don’t care” for comparison purposes. In this case, either
a 1 or a 0 value are acceptable on the incoming slave address. Additionally, if the GC bit in register SMB0ADR is
set to 1, hardware will recognize the General Call Address (0x00). Table 24.4 shows some example parameter
settings and the slave addresses that will be recognized by hardware under those conditions.
Table 24.4. Hardware Address Recognition Examples (EHACK = 1)
Hardware Slave Address
Slave Address Mask
SLV
SLVM
GC bit
Slave Addresses Recognized by
Hardware
0x34
0x34
0x7F
0
0x34
0x7F
1
0x34, 0x00 (General Call)
0x34
0x7E
0
0x34, 0x35
0x34
0x7E
1
0x34, 0x35, 0x00 (General Call)
0x70
0x73
0
0x70, 0x74, 0x78, 0x7C
24.4.6. 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 data register when the SI flag is set. Software should not attempt
to access the SMB0DAT register when the SMBus is enabled 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 shifted out MSB first. After a byte 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 present on the bus. In the event of lost arbitration, the transition from
master transmitter to slave receiver is made with the correct data or address in SMB0DAT.
236
Preliminary Rev 0.6
24.5. SMBus Transfer Modes
The SMBus interface may be configured to operate as master and/or slave. At any particular time, it will be
operating in one of the following four modes: Master Transmitter, Master Receiver, Slave Transmitter, or Slave
Receiver. The SMBus interface enters Master Mode any time a START is generated, and remains in Master Mode
until it loses an arbitration or generates a STOP. An SMBus interrupt is generated at the end of all SMBus byte
frames. The position of the ACK interrupt when operating as a receiver depends on whether hardware ACK
generation is enabled. As a receiver, the interrupt for an ACK occurs before the ACK with hardware ACK
generation disabled, and after the ACK when hardware ACK generation is enabled. As a transmitter, interrupts
occur after the ACK, regardless of whether hardware ACK generation is enabled or not.
24.5.1. Write Sequence (Master)
During a write sequence, an SMBus master writes data to a slave device. The master in this transfer will be a
transmitter during the address byte, and a transmitter during all data bytes. The SMBus interface generates 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 transmits one or more bytes of serial
data. After each byte is transmitted, an acknowledge bit is generated by the slave. The transfer is ended when the
STO bit is set and a STOP is generated. The interface will switch to Master Receiver Mode if SMB0DAT is not
written following a Master Transmitter interrupt. Figure 24.5 shows a typical master write sequence. Two transmit
data bytes are shown, though any number of bytes may be transmitted. Notice that all of the “data byte transferred”
interrupts occur after the ACK cycle in this mode, regardless of whether hardware ACK generation is enabled.
Interrupts with Hardware ACK Enabled (EHACK = 1)
S
SLA
W
A
Data Byte
A
Data Byte
A
P
Interrupts with Hardware ACK Disabled (EHACK = 0)
S = START
P = STOP
A = ACK
W = WRITE
SLA = Slave Address
Received by SMBus
Interface
Transmitted by
SMBus Interface
Figure 24.5. Typical Master Write Sequence
Preliminary Rev 0.6
237
System Management Bus / I2C (SMBus0)
C8051F85x/86x
System Management Bus / I2C (SMBus0)
C8051F85x/86x
24.5.2. Read Sequence (Master)
During a read sequence, an SMBus master reads data from a slave device. The master in this transfer will be a
transmitter during the address byte, and a receiver during all data bytes. The SMBus interface generates 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 on SDA
while the SMBus outputs the serial clock. The slave transmits one or more bytes of serial data.
If hardware ACK generation is disabled, the ACKRQ is set to 1 and an interrupt is generated after each received
byte. Software must write the ACK bit at that time to ACK or NACK the received byte.
With hardware ACK generation enabled, the SMBus hardware will automatically generate the ACK/NACK, and
then post the interrupt. It is important to note that the appropriate ACK or NACK value should be set up by
the software prior to receiving the byte when hardware ACK generation is enabled.
Writing a 1 to the ACK bit generates an ACK; writing a 0 generates a NACK. Software should write a 0 to the ACK
bit for the last data transfer, to transmit a NACK. The interface exits Master Receiver Mode after the STO bit is set
and a STOP is generated. The interface will switch to Master Transmitter Mode if SMB0DAT is written while an
active Master Receiver. Figure 24.6 shows a typical master read sequence. Two received data bytes are shown,
though any number of bytes may be received. Notice that the ‘data byte transferred’ interrupts occur at different
places in the sequence, depending on whether hardware ACK generation is enabled. The interrupt occurs before
the ACK with hardware ACK generation disabled, and after the ACK when hardware ACK generation is enabled.
Interrupts with Hardware ACK Enabled (EHACK = 1)
S
SLA
R
A
Data Byte
A
Data Byte
N
Interrupts with Hardware ACK Disabled (EHACK = 0)
S = START
P = STOP
A = ACK
N = NACK
R = READ
SLA = Slave Address
Received by SMBus
Interface
Transmitted by
SMBus Interface
Figure 24.6. Typical Master Read Sequence
238
Preliminary Rev 0.6
P
24.5.3. Write Sequence (Slave)
During a write sequence, an SMBus master writes data to a slave device. The slave in this transfer will be a
receiver during the address byte, and a receiver during all data bytes. When slave events are enabled (INH = 0),
the interface enters Slave Receiver Mode when a START followed by a slave address and direction bit (WRITE in
this case) is received. If hardware ACK generation is disabled, upon entering Slave Receiver Mode, an interrupt is
generated and the ACKRQ bit is set. The software must respond to the received slave address with an ACK, or
ignore the received slave address with a NACK. If hardware ACK generation is enabled, the hardware will apply
the ACK for a slave address which matches the criteria set up by SMB0ADR and SMB0ADM. The interrupt will
occur after the ACK cycle.
If the received slave address is ignored (by software or hardware), slave interrupts will be inhibited until the next
START is detected. If the received slave address is acknowledged, zero or more data bytes are received.
If hardware ACK generation is disabled, the ACKRQ is set to 1 and an interrupt is generated after each received
byte. Software must write the ACK bit at that time to ACK or NACK the received byte.
With hardware ACK generation enabled, the SMBus hardware will automatically generate the ACK/NACK, and
then post the interrupt. It is important to note that the appropriate ACK or NACK value should be set up by
the software prior to receiving the byte when hardware ACK generation is enabled.
The interface exits Slave Receiver Mode after receiving a STOP. The interface will switch to Slave Transmitter
Mode if SMB0DAT is written while an active Slave Receiver. Figure 24.7 shows a typical slave write sequence. Two
received data bytes are shown, though any number of bytes may be received. Notice that the ‘data byte
transferred’ interrupts occur at different places in the sequence, depending on whether hardware ACK generation
is enabled. The interrupt occurs before the ACK with hardware ACK generation disabled, and after the ACK when
hardware ACK generation is enabled.
Interrupts with Hardware ACK Enabled (EHACK = 1)
S
SLA
W
A
Data Byte
A
Data Byte
A
P
Interrupts with Hardware ACK Disabled (EHACK = 0)
S = START
P = STOP
A = ACK
W = WRITE
SLA = Slave Address
Received by SMBus
Interface
Transmitted by
SMBus Interface
Figure 24.7. Typical Slave Write Sequence
Preliminary Rev 0.6
239
System Management Bus / I2C (SMBus0)
C8051F85x/86x
System Management Bus / I2C (SMBus0)
C8051F85x/86x
24.5.4. Read Sequence (Slave)
During a read sequence, an SMBus master reads data from a slave device. The slave in this transfer will be a
receiver during the address byte, and a transmitter during all data bytes. When slave events are enabled (INH = 0),
the interface enters Slave Receiver Mode (to receive the slave address) when a START followed by a slave
address and direction bit (READ in this case) is received. If hardware ACK generation is disabled, upon entering
Slave Receiver Mode, an interrupt is generated and the ACKRQ bit is set. The software must respond to the
received slave address with an ACK, or ignore the received slave address with a NACK. If hardware ACK
generation is enabled, the hardware will apply the ACK for a slave address which matches the criteria set up by
SMB0ADR and SMB0ADM. The interrupt will occur after the ACK cycle.
If the received slave address is ignored (by software or hardware), slave interrupts will be inhibited until the next
START is detected. If the received slave address is acknowledged, zero or more data bytes are 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 written to before SI is cleared (an error condition may be
generated if SMB0DAT is written following a received NACK while in slave transmitter mode). The interface exits
slave transmitter mode after receiving a STOP. The interface will switch to slave receiver mode if SMB0DAT is not
written following a Slave Transmitter interrupt. Figure 24.8 shows a typical slave read sequence. Two transmitted
data bytes are shown, though any number of bytes may be transmitted. Notice that all of the “data byte transferred”
interrupts occur after the ACK cycle in this mode, regardless of whether hardware ACK generation is enabled.
Interrupts with Hardware ACK Enabled (EHACK = 1)
S
SLA
R
A
Data Byte
A
Data Byte
N
P
Interrupts with Hardware ACK Disabled (EHACK = 0)
S = START
P = STOP
N = NACK
R = READ
SLA = Slave Address
Received by SMBus
Interface
Transmitted by
SMBus Interface
Figure 24.8. Typical Slave Read Sequence
24.6. SMBus Status Decoding
The current SMBus status can be easily decoded using the SMB0CN register. The appropriate actions to take in
response to an SMBus event depend on whether hardware slave address recognition and ACK generation is
enabled or disabled. Table 24.5 describes the typical actions when hardware slave address recognition and ACK
generation is disabled. Table 24.6 describes the typical actions when hardware slave address recognition and ACK
generation is enabled. In the tables, STATUS VECTOR refers to the four upper bits of SMB0CN: MASTER,
TXMODE, STA, and STO. The shown response options are only the typical responses; application-specific
procedures are allowed as long as they conform to the SMBus specification. Highlighted responses are allowed by
hardware but do not conform to the SMBus specification.
240
Preliminary Rev 0.6
1100
Set STA to restart transfer.
1
0 X
1110
Abort transfer.
0
1 X
—
Load next data byte into SMB0DAT.
0
0 X
1100
End transfer with STOP.
0
1 X
—
End transfer with STOP and start 1
another transfer.
1 X
—
Send repeated START.
1
0 X
1110
Switch to Master Receiver Mode 0
(clear SI without writing new data
to SMB0DAT).
0 X
1000
Acknowledge received byte;
Read SMB0DAT.
0
0
1
1000
Send NACK to indicate last byte, 0
and send STOP.
1
0
—
Send NACK to indicate last byte, 1
and send STOP followed by
START.
1
0
1110
Send ACK followed by repeated 1
A master data byte was received; ACK
START.
requested.
Send NACK to indicate last byte, 1
and send repeated START.
0
1
1110
0
0
1110
0
1
0
1
0 X
Next Status
0 X
0
0
ACK
0
0 X A master START was generated.
1100
1000
Load slave address + R/W into
SMB0DAT.
0
0
Typical Response Options
STO
ACK
ARBLOST
ACKRQ
Vector
Status
Mode
Master Receiver
Master Transmitter
1110
Current SMbus State
STA
Values to
Write
Values Read
Vector Expected
Table 24.5. SMBus Status Decoding: Hardware ACK Disabled (EHACK = 0)
A master data or address byte was
transmitted; NACK received.
A master data or address byte was
transmitted; ACK received.
Send ACK and switch to Master
Transmitter Mode (write to
SMB0DAT before clearing SI).
0
0
1
1100
Send NACK and switch to Master Transmitter Mode (write to
SMB0DAT before clearing SI).
0
0
0
1100
Preliminary Rev 0.6
241
System Management Bus / I2C (SMBus0)
C8051F85x/86x
0
A slave byte was transmitted; NACK
received.
No action required (expecting
STOP condition).
0
0 X
0001
0
0
1
A slave byte was transmitted; ACK
received.
Load SMB0DAT with next data
byte to transmit.
0
0 X
0100
0
1 X
A Slave byte was transmitted; error
detected.
No action required (expecting
Master to end transfer).
0
0 X
0001
0
0 X
—
0
0
1
0000
If Read, Load SMB0DAT with
0
data byte; ACK received address
0
1
0100
NACK received address.
0
0
0
—
If Write, Acknowledge received
address
0
0
1
0000
0
If Read, Load SMB0DAT with
data byte; ACK received address
0
1
0100
NACK received address.
0
0
0
—
Reschedule failed transfer;
NACK received address.
1
0
0
1110
0
0 X
—
No action required (transfer
complete/aborted).
0
0
0
—
Acknowledge received byte;
Read SMB0DAT.
0
0
1
0000
NACK received byte.
0
0
0
—
Abort failed transfer.
0
0 X
—
Reschedule failed transfer.
1
0 X
1110
Abort failed transfer.
0
0 X
—
Reschedule failed transfer.
1
0 X
1110
Abort failed transfer.
0
0
0
—
Reschedule failed transfer.
1
0
0
1110
An illegal STOP or bus error was
0 X X detected while a Slave Transmission
was in progress.
1
0 X
A slave address + R/W was received;
ACK requested.
Slave Receiver
0010
1
242
If Write, Acknowledge received
address
0
A STOP was detected while addressed
Clear STO.
0 X as a Slave Transmitter or Slave
Receiver.
1
1 X
Lost arbitration while attempting a
STOP.
1
0 X
A slave byte was received; ACK
requested.
0001
0000
Lost arbitration as master; slave
1 X address + R/W received; ACK
requested.
Clear STO.
0010
0
1 X
Lost arbitration while attempting a
repeated START.
0001
0
1 X
Lost arbitration due to a detected
STOP.
0000
1
1 X
Lost arbitration while transmitting a
data byte as master.
Preliminary Rev 0.6
ACK
0
Typical Response Options
STO
ACK
0
Current SMbus State
STA
ARBLOST
0101
ACKRQ
Vector
Status
Mode
Slave Transmitter
0100
Next Status
Values to
Write
Values Read
Vector Expected
Table 24.5. SMBus Status Decoding: Hardware ACK Disabled (EHACK = 0) (Continued)
Bus Error Condition
System Management Bus / I2C (SMBus0)
C8051F85x/86x
0 X A master START was generated.
0
0
0
A master data or address byte was
transmitted; NACK received.
1100
0
0
0
A master data or address byte was
1
transmitted; ACK received.
0
0
A master data byte was received;
NACK sent (last byte).
Next Status
STO
Load slave address + R/W into
SMB0DAT.
0
0 X
1100
Set STA to restart transfer.
1
0 X
1110
Abort transfer.
0
1 X
—
Load next data byte into SMB0DAT.
0
0 X
1100
End transfer with STOP.
0
1 X
—
End transfer with STOP and start 1
another transfer.
1 X
—
Send repeated START.
0 X
1110
Switch to Master Receiver Mode 0
(clear SI without writing new data
to SMB0DAT). Set ACK for initial
data byte.
0
1
1000
Set ACK for next data byte;
Read SMB0DAT.
0
0
1
1000
0
0
0
1000
1
0
0
1110
Switch to Master Transmitter
0
Mode (write to SMB0DAT before
clearing SI).
0 X
1100
Read SMB0DAT; send STOP.
0
1
0
—
Read SMB0DAT; Send STOP
followed by START.
1
1
0
1110
Initiate repeated START.
1
0
0
1110
0 X
1100
Set NACK to indicate next data
byte as the last data byte;
A master data byte was received; ACK Read SMB0DAT.
1
sent.
Initiate repeated START.
1000
0
Typical Response Options
STA
ACK
0
0
Master Receiver
ARBLOST
ACKRQ
Vector
Status
Mode
Master Transmitter
1110
Current SMbus State
ACK
Values to
Write
Values Read
Vector Expected
Table 24.6. SMBus Status Decoding: Hardware ACK Enabled (EHACK = 1)
1
Switch to Master Transmitter
0
Mode (write to SMB0DAT before
clearing SI).
Preliminary Rev 0.6
243
System Management Bus / I2C (SMBus0)
C8051F85x/86x
0
A slave byte was transmitted; NACK
received.
No action required (expecting
STOP condition).
0
0 X
0001
0
0
1
A slave byte was transmitted; ACK
received.
Load SMB0DAT with next data
byte to transmit.
0
0 X
0100
0
1 X
A Slave byte was transmitted; error
detected.
No action required (expecting
Master to end transfer).
0
0 X
0001
0
0 X
—
If Write, Set ACK for first data
A slave address + R/W was received; byte.
0 X
ACK sent.
If Read, Load SMB0DAT with
data byte
0
0
1
0000
0
0 X
0100
If Write, Set ACK for first data
byte.
0
0
1
0000
If Read, Load SMB0DAT with
data byte
0
0 X
0100
Reschedule failed transfer
1
0 X
1110
0
0 X
—
No action required (transfer
complete/aborted).
0
0
0
—
Set ACK for next data byte;
Read SMB0DAT.
0
0
1
0000
Set NACK for next data byte;
Read SMB0DAT.
0
0
0
0000
Abort failed transfer.
0
0 X
—
Reschedule failed transfer.
1
0 X
1110
Abort failed transfer.
0
0 X
—
Reschedule failed transfer.
1
0 X
1110
Abort failed transfer.
0
0 X
—
Reschedule failed transfer.
1
0 X
1110
An illegal STOP or bus error was
0 X X detected while a Slave Transmission
was in progress.
0
Slave Receiver
0010
244
0
1 X
Lost arbitration as master; slave
address + R/W received; ACK sent.
0
A STOP was detected while
0 X addressed as a Slave Transmitter or
Slave Receiver.
0
1 X
0001
Lost arbitration while attempting a
STOP.
0000
0
0 X A slave byte was received.
0010
0
1 X
Lost arbitration while attempting a
repeated START.
0001
0
1 X
Lost arbitration due to a detected
STOP.
0000
0
1 X
Lost arbitration while transmitting a
data byte as master.
Clear STO.
Clear STO.
Preliminary Rev 0.6
ACK
0
STO
ACK
0
STA
ARBLOST
0101
Typical Response Options
ACKRQ
Vector
Status
Mode
Slave Transmitter
0100
Current SMbus State
Next Status
Values to
Write
Values Read
Vector Expected
Table 24.6. SMBus Status Decoding: Hardware ACK Enabled (EHACK = 1) (Continued)
Bus Error Condition
System Management Bus / I2C (SMBus0)
C8051F85x/86x
24.7. I2C / SMBus Control Registers
Register 24.1. SMB0CF: SMBus0 Configuration
Bit
7
6
5
4
3
2
1
Name
ENSMB
INH
BUSY
EXTHOLD
SMBTOE
SMBFTE
SMBCS
Type
RW
RW
R
RW
RW
RW
RW
Reset
0
0
0
0
0
0
0
0
0
SFR Address: 0xC1
Table 24.7. SMB0CF Register Bit Descriptions
Bit
Name
7
ENSMB
Function
SMBus0 Enable.
This bit enables the SMBus0 interface when set to 1. When enabled, the interface constantly monitors the SDA and SCL pins.
6
INH
SMBus0 Slave Inhibit.
When this bit is set to logic 1, the SMBus0 does not generate an interrupt when slave
events occur. This effectively removes the SMBus0 slave from the bus. Master Mode
interrupts are not affected.
5
BUSY
SMBus0 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 STOP or free-timeout is sensed.
4
EXTHOLD
SMBus0 Setup and Hold Time Extension Enable.
This bit controls the SDA setup and hold times.
0: SDA Extended Setup and Hold Times disabled.
1: SDA Extended Setup and Hold Times enabled.
3
SMBTOE
SMBus0 SCL Timeout Detection Enable.
This bit enables SCL low timeout detection. If set to logic 1, the SMBus0 forces Timer 3
to reload while SCL is high and allows Timer 3 to count when SCL goes low. If Timer 3 is
configured to Split Mode, only the High Byte of the timer is held in reload while SCL is
high. Timer 3 should be programmed to generate interrupts at 25 ms, and the Timer 3
interrupt service routine should reset SMBus0 communication.
2
SMBFTE
SMBus0 Free Timeout 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
SMBus0 Clock Source Selection.
These two bits select the SMBus0 clock source, which is used to generate the SMBus0
bit rate. See the SMBus clock timing section for additional details.
00: Timer 0 Overflow
01: Timer 1 Overflow
10: Timer 2 High Byte Overflow
11: Timer 2 Low Byte Overflow
Preliminary Rev 0.6
245
System Management Bus / I2C (SMBus0)
C8051F85x/86x
System Management Bus / I2C (SMBus0)
C8051F85x/86x
Register 24.2. SMB0TC: SMBus0 Timing and Pin Control
Bit
7
6
Name
SWAP
Reserved
SDD
Type
RW
R
RW
Reset
0
0
5
4
0
3
0
0
2
0
1
0
0
0
SFR Address: 0xAC
Table 24.8. SMB0TC Register Bit Descriptions
Bit
Name
7
SWAP
Function
SMBus0 Swap Pins.
This bit swaps the order of the SMBus0 pins on the crossbar.
0: SDA is mapped to the lower-numbered port pin, and SCL is mapped to the highernumbered port pin.
1: SCL is mapped to the lower-numbered port pin, and SDA is mapped to the highernumbered port pin.
6:2
Reserved
1:0
SDD
Must write reset value.
SMBus0 Start Detection Window.
These bits increase the hold time requirement between SDA falling and SCL falling for
START detection.
00: No additional hold time window (0-1 SYSCLK).
01: Increase hold time window to 2-3 SYSCLKs.
10: Increase hold time window to 4-5 SYSCLKs.
11: Increase hold time window to 8-9 SYSCLKs.
246
Preliminary Rev 0.6
Register 24.3. SMB0CN: SMBus0 Control
Bit
7
6
5
4
3
2
1
0
Name
MASTER
TXMODE
STA
STO
ACKRQ
ARBLOST
ACK
SI
Type
R
R
RW
RW
R
R
RW
RW
Reset
0
0
0
0
0
0
0
0
SFR Address: 0xC0 (bit-addressable)
Table 24.9. SMB0CN Register Bit Descriptions
Bit
Name
7
MASTER
Function
SMBus0 Master/Slave Indicator.
This read-only bit indicates when the SMBus0 is operating as a master.
0: SMBus0 operating in slave mode.
1: SMBus0 operating in master mode.
6
TXMODE
SMBus0 Transmit Mode Indicator.
This read-only bit indicates when the SMBus0 is operating as a transmitter.
0: SMBus0 in Receiver Mode.
1: SMBus0 in Transmitter Mode.
5
STA
SMBus0 Start Flag.
When reading STA, a 1 indicates that a start or repeated start condition was detected on
the bus.
Writing a 1 to the STA bit initiates a start or repeated start on the bus.
4
STO
SMBus0 Stop Flag.
When reading STO, a 1 indicates that a stop condition was detected on the bus (in slave
mode) or is pending (in master mode).
When acting as a master, writing a 1 to the STO bit initiates a stop condition on the bus.
This bit is cleared by hardware.
3
ACKRQ
SMBus0 Acknowledge Request.
0: No ACK requested.
1: ACK requested.
2
ARBLOST
SMBus0 Arbitration Lost Indicator.
0: No arbitration error.
1: Arbitration error occurred.
1
ACK
SMBus0 Acknowledge.
When read as a master, the ACK bit indicates whether an ACK (1) or NACK (0) is
received during the most recent byte transfer.
As a slave, this bit should be written to send an ACK (1) or NACK (0) to a master
request. Note that the logic level of the ACK bit on the SMBus interface is inverted from
the logic of the register ACK bit.
Preliminary Rev 0.6
247
System Management Bus / I2C (SMBus0)
C8051F85x/86x
System Management Bus / I2C (SMBus0)
C8051F85x/86x
Table 24.9. SMB0CN Register Bit Descriptions
Bit
Name
0
SI
Function
SMBus0 Interrupt Flag.
This bit is set by hardware to indicate that the current SMBus0 state machine operation
(such as writing a data or address byte) is complete. While SI is set, SCL0 is held low
and SMBus0 is stalled. SI0 must be cleared by software. Clearing SI0 initiates the next
SMBus0 state machine operation.
248
Preliminary Rev 0.6
Register 24.4. SMB0ADR: SMBus0 Slave Address
Bit
7
6
5
4
3
2
1
0
Name
SLV
GC
Type
RW
RW
Reset
0
0
0
0
0
0
0
0
SFR Address: 0xD7
Table 24.10. SMB0ADR Register Bit Descriptions
Bit
Name
7:1
SLV
Function
SMBus Hardware Slave Address.
Defines the SMBus0 Slave Address(es) for automatic hardware acknowledgement. Only
address bits which have a 1 in the corresponding bit position in SLVM are checked
against the incoming address. This allows multiple addresses to be recognized.
0
GC
General Call Address Enable.
When hardware address recognition is enabled (EHACK = 1), this bit will determine
whether the General Call Address (0x00) is also recognized by hardware.
0: General Call Address is ignored.
1: General Call Address is recognized.
Preliminary Rev 0.6
249
System Management Bus / I2C (SMBus0)
C8051F85x/86x
System Management Bus / I2C (SMBus0)
C8051F85x/86x
Register 24.5. SMB0ADM: SMBus0 Slave Address Mask
Bit
7
6
5
4
3
2
1
0
Name
SLVM
EHACK
Type
RW
RW
Reset
1
1
1
1
1
1
1
0
SFR Address: 0xD6
Table 24.11. SMB0ADM Register Bit Descriptions
Bit
Name
7:1
SLVM
Function
SMBus0 Slave Address Mask.
Defines which bits of register SMB0ADR are compared with an incoming address byte,
and which bits are ignored. Any bit set to 1 in SLVM enables comparisons with the corresponding bit in SLV. Bits set to 0 are ignored (can be either 0 or 1 in the incoming
address).
0
EHACK
Hardware Acknowledge Enable.
Enables hardware acknowledgement of slave address and received data bytes.
0: Firmware must manually acknowledge all incoming address and data bytes.
1: Automatic slave address recognition and hardware acknowledge is enabled.
250
Preliminary Rev 0.6
Register 24.6. SMB0DAT: SMBus0 Data
Bit
7
6
5
4
Name
SMB0DAT
Type
RW
Reset
0
0
0
0
3
2
1
0
0
0
0
0
SFR Address: 0xC2
Table 24.12. SMB0DAT Register Bit Descriptions
Bit
Name
7:0
SMB0DAT
Function
SMBus0 Data.
The SMB0DAT register contains a byte of data to be transmitted on the SMBus0 serial
interface or a byte that has just been received on the SMBus0 serial interface. The CPU
can safely read from or write to this register whenever the SI serial interrupt flag 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.
Preliminary Rev 0.6
251
System Management Bus / I2C (SMBus0)
C8051F85x/86x
Timers (Timer0, Timer1, Timer2 and Timer3)
C8051F85x/86x
25. Timers (Timer0, Timer1, Timer2 and Timer3)
Each MCU in the C8051F85x/86x family includes four counter/timers: two are 16-bit counter/timers compatible with
those found in the standard 8051, and two are 16-bit auto-reload timers for timing peripherals 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 and
Timer 3 are also identical and offer both 16-bit and split 8-bit timer functionality with auto-reload capabilities.
Timer 2 and Timer 3 both offer a capture function, but are different in their system-level connections. Timer 2 is
capable of performing a capture function on an external signal input routed through the crossbar, while the Timer 3
capture is dedicated to the low-frequency oscillator output. Table 25.1 summarizes the modes available to each
timer.
Table 25.1. Timer Modes
Timer 0 and Timer 1 Modes
Timer 2 Modes
Timer 3 Modes
13-bit counter/timer
16-bit timer with auto-reload
16-bit timer with auto-reload
16-bit counter/timer
Two 8-bit timers with auto-reload
Two 8-bit timers with auto-reload
8-bit counter/timer with auto-reload
Input pin capture
Low-frequency oscillator capture
Two 8-bit counter/timers
(Timer 0 only)
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.
Timer 0/1 may then be configured to use this pre-scaled clock signal or the system clock. Timer 2 and Timer 3 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
incremented on each high-to-low transition at the selected input pin (T0 or T1). Events with a frequency of up to
one-fourth the system clock frequency can be counted. The input signal need not be periodic, but it must be held at
a given level for at least two full system clock cycles to ensure the level is properly sampled.
All four timers are capable of clocking other peripherals and triggering events in the system. The individual
peripherals select which timer to use for their respective functions. Table 25.2 summarizes the peripheral
connections for each timer. Note that the Timer 2 and Timer 3 high overflows apply to the full timer when operating
in 16-bit mode or the high-byte timer when operating in 8-bit split mode.
Table 25.2. Timer Peripheral Clocking / Event Triggering
Function
T0
Overflow
UART0 Baud Rate
SMBus0 Clock Rate
T1
Overflow
T2 High
Overflow
T2 Low
Overflow
X
X
T3 High
Overflow
T3 Low
Overflow
X
X
X
SMBus0 SCL Low Timeout
X
PCA0 Clock
X
ADC0 Conversion Start
X
X*
X*
X*
*Note: The high-side overflow is used when the timer is in16-bit mode. The low-side overflow is used in 8-bit mode.
252
Preliminary Rev 0.6
X*
25.1. Timer 0 and Timer 1
Timer 0 and Timer 1 are each implemented as a16-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
Timer 1 as well as indicate status. Timer 0 interrupts can be enabled by setting the ET0 bit in the IE register.
Timer 1 interrupts can be enabled by setting the ET1 bit in the IE register. 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 for the operating modes described below.
Preliminary Rev 0.6
253
Timers (Timer0, Timer1, Timer2 and Timer3)
C8051F85x/86x
Timers (Timer0, Timer1, Timer2 and Timer3)
C8051F85x/86x
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 should be masked out or ignored when
reading. As the 13-bit timer register increments and overflows from 0x1FFF (all ones) to 0x0000, the timer overflow
flag TF0 in TCON is set and an interrupt will occur if Timer 0 interrupts are enabled.
The CT0 bit in the TMOD register selects the counter/timer's clock source. When CT0 is set to logic 1, high-to-low
transitions at the selected Timer 0 input pin (T0) increment the timer register. Clearing CT 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.
Setting the TR0 bit 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. Setting GATE0 to 1 allows the timer to be controlled by the
external input signal INT0, facilitating pulse width measurements
TR0
GATE0
INT0
Counter/Timer
0
X
X
Disabled
1
0
X
Enabled
1
1
0
Disabled
1
1
1
Enabled
Note: X = Don't Care
Setting TR0 does not force the timer to reset. The timer registers should be loaded with the desired initial value
before the timer is enabled.
TL1 and TH1 form the 13-bit register for Timer 1 in the same manner as described above 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 INT1 is
used with Timer 1; the /INT1 polarity is defined by bit IN1PL in register IT01CF.
T0M
Pre-scaled Clock
CT0
0
0
SYSCLK
1
1
T0
TR0
TCLK
GATE0
INT0
IN0PL
TL0
(5 bits)
TH0
(8 bits)
TF0
(Interrupt Flag)
XOR
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.
254
Preliminary Rev 0.6
25.1.3. Mode 2: 8-bit Counter/Timer with Auto-Reload
Mode 2 configures Timer 0 and Timer 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
enables the timer when either GATE0 in the TMOD register is logic 0 or when the input signal INT0 is active as
defined by bit IN0PL in register IT01CF.
T0M
Pre-scaled Clock
CT0
0
0
SYSCLK
1
1
T0
TR0
TCLK
GATE0
INT0
IN0PL
TL0
(8 bits)
TH0
(8 bits)
XOR
TF0
(Interrupt Flag)
Reload
Figure 25.2. T0 Mode 2 Block Diagram
Preliminary Rev 0.6
255
Timers (Timer0, Timer1, Timer2 and Timer3)
C8051F85x/86x
Timers (Timer0, Timer1, Timer2 and Timer3)
C8051F85x/86x
25.1.4. Mode 3: Two 8-bit Counter/Timers (Timer 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, CT0, GATE0 and TF0. TL0 can
use either the system clock or an external input signal as its timebase. The TH0 register is restricted to a timer
function sourced by the system clock or prescaled clock. TH0 is enabled using the 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 settings. 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.
T0M
CT0
Pre-scaled Clock
0
TH0
(8 bits)
TR1
SYSCLK
1
TF1
(Interrupt Flag)
0
1
T0
TR0
TCLK
GATE0
INT0
IN0PL
TL0
(8 bits)
XOR
Figure 25.3. T0 Mode 3 Block Diagram
256
Preliminary Rev 0.6
TF0
(Interrupt Flag)
25.2. Timer 2 and Timer 3
Timer 2 and Timer 3 are functionally equivalent, with the only differences being the top-level connections to other
parts of the system, as detailed in Table 25.1 and Table 25.2.
The timers are 16 bits wide, formed by two 8-bit SFRs: TMRnL (low byte) and TMRnH (high byte). Each timer may
operate in 16-bit auto-reload mode or (split) 8-bit auto-reload mode. The TnSPLIT bit in TMRnCN defines the timer
operation mode.
The timers may be clocked by the system clock, the system clock divided by 12, or the external oscillator source
divided by 8. Note that the external oscillator source divided by 8 is synchronized with the system clock.
25.2.1. 16-bit Timer with Auto-Reload
When TnSPLIT is zero, the timer operates as a 16-bit timer with auto-reload. In this mode, the timer may be
configured to clock from 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 reload
registers (TMRnRLH and TMRnRLL) is loaded into the main timer count register as shown in Figure 25.4, and the
High Byte Overflow Flag (TFnH) is set. If the timer interrupts are enabled, an interrupt will be generated on each
timer overflow. Additionally, if the timer interrupts are enabled and the TFnLEN bit is set, an interrupt will be
generated each time the lower 8 bits (TMRnL) overflow from 0xFF to 0x00.
TnXCLK
SYSCLK / 12
TnML
TFnL
Overflow
0
0
EXTCLK / 8
SYSCLK
1
TRn
TCLK
TMRnL
TMRnH
TFnH
Overflow
1
Interrupt
TFnLEN
TMRnRLL TMRnRLH
Reload
Figure 25.4. 16-Bit Mode Block Diagram
Preliminary Rev 0.6
257
Timers (Timer0, Timer1, Timer2 and Timer3)
C8051F85x/86x
Timers (Timer0, Timer1, Timer2 and Timer3)
C8051F85x/86x
25.2.2. 8-bit Timers with Auto-Reload
When TnSPLIT is set, the timer operates as two 8-bit timers (TMRnH and TMRnL). Both 8-bit timers operate in
auto-reload mode as shown in Figure 25.5. TMRnRLL holds the reload value for TMRnL; TMRnRLH holds the
reload value for TMRnH. The TRn bit in TMRnCN handles the run control for TMRnH. TMRnL is always running
when configured for 8-bit auto-reload mode.
Each 8-bit timer may be configured to clock from SYSCLK, SYSCLK divided by 12, or the external oscillator clock
source divided by 8. The Clock Select bits (TnMH and TnML in CKCON) select either SYSCLK or the clock defined
by the External Clock Select bit (TnXCLK in TMRnCN), as follows:
TnMH
TnXCLK
0
0
0
1
TMRnH Clock Source
TnML
TnXCLK
TMRnL Clock Source
SYSCLK / 12
0
0
SYSCLK / 12
1
External Clock / 8
0
1
External Clock / 8
X
SYSCLK
1
X
SYSCLK
The TFnH bit is set when TMRnH overflows from 0xFF to 0x00; the TFnL bit is set when TMRnL overflows from
0xFF to 0x00. When timer interrupts are enabled, an interrupt is generated each time TMRnH overflows. If tmier
interrupts are enabled and TFnLEN is set, an interrupt is generated each time either TMRnL or TMRnH overflows.
When TFnLEN is enabled, software must check the TFnH and TFnL flags to determine the source of the timer
interrupt. The TFnH and TFnL interrupt flags are not cleared by hardware and must be manually cleared by
software.
TnXCLK
TnMH
SYSCLK / 12
0
External Clock / 8
1
TMRnRLH
0
1
SYSCLK
TRn
TCLK
TMRnH
TMRnRLL
TnML
Reload
TFnH
Overflow
Reload
Interrupt
TFnLEN
1
TCLK
TMRnL
0
Figure 25.5. 8-Bit Mode Block Diagram
258
Preliminary Rev 0.6
TFnL
Overflow
25.2.3. Capture Mode
Capture mode allows an external input (Timer 2) or the low-frequency oscillator clock (Timer 3) to be measured
against the system clock or an external oscillator source. The timer can be clocked from the system clock, the
system clock divided by 12, or the external oscillator divided by 8, depending on the TnML, and TnXCLK settings.
Setting TFnCEN to 1 enables Capture Mode. In this mode, TnSPLIT should be set to 0, as the full 16-bit timer is
used. Upon a falling edge of the input capture signal, the contents of the timer register (TMRnH:TMRnL) are loaded
into the reload registers (TMRnRLH:TMRnRLL) and the TFnH flag is set. By recording the difference between two
successive timer capture values, the period of the captured signal can be determined with respect to the selected
timer clock.
TnXCLK
SYSCLK / 12
TnML
0
0
External Clock / 8
SYSCLK
T2 Pin (Timer 2)
L-F Oscillator (Timer 3)
1
TRn
TCLK
TMRnL
TMRnH
Capture
1
TFnCEN
TMRnRLL TMRnRLH
TFnH
(Interrupt)
Figure 25.6. Capture Mode Block Diagram
Preliminary Rev 0.6
259
Timers (Timer0, Timer1, Timer2 and Timer3)
C8051F85x/86x
Timers (Timer0, Timer1, Timer2 and Timer3)
C8051F85x/86x
25.3. Timer Control Registers
Register 25.1. CKCON: Clock Control
Bit
7
6
5
4
3
2
1
0
Name
T3MH
T3ML
T2MH
T2ML
T1M
T0M
SCA
Type
RW
RW
RW
RW
RW
RW
RW
Reset
0
0
0
0
0
0
0
0
SFR Address: 0x8E
Table 25.3. CKCON Register Bit Descriptions
Bit
Name
7
T3MH
Function
Timer 3 High Byte Clock Select.
Selects the clock supplied to the Timer 3 high byte (split 8-bit timer mode only).
0: Timer 3 high byte uses the clock defined by the T3XCLK bit in TMR3CN.
1: Timer 3 high byte uses the system clock.
6
T3ML
Timer 3 Low Byte Clock Select.
Selects the clock supplied to Timer 3. Selects the clock supplied to the lower 8-bit timer
in split 8-bit timer mode.
0: Timer 3 low byte uses the clock defined by the T3XCLK bit in TMR3CN.
1: Timer 3 low byte uses the system clock.
5
T2MH
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.
4
T2ML
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.
3
T1M
Timer 1 Clock Select.
Selects the clock source supplied to Timer 1. Ignored when C/T1 is set to 1.
0: Timer 1 uses the clock defined by the prescale field, SCA.
1: Timer 1 uses the system clock.
2
T0M
Timer 0 Clock Select.
Selects the clock source supplied to Timer 0. Ignored when C/T0 is set to 1.
0: Counter/Timer 0 uses the clock defined by the prescale field, SCA.
1: Counter/Timer 0 uses the system clock.
260
Preliminary Rev 0.6
Table 25.3. CKCON Register Bit Descriptions
Bit
Name
1:0
SCA
Function
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)
Preliminary Rev 0.6
261
Timers (Timer0, Timer1, Timer2 and Timer3)
C8051F85x/86x
Timers (Timer0, Timer1, Timer2 and Timer3)
C8051F85x/86x
Register 25.2. TCON: Timer 0/1 Control
Bit
7
6
5
4
3
2
1
0
Name
TF1
TR1
TF0
TR0
IE1
IT1
IE0
IT0
Type
RW
RW
RW
RW
RW
RW
RW
RW
Reset
0
0
0
0
0
0
0
0
SFR Address: 0x88 (bit-addressable)
Table 25.4. TCON Register Bit Descriptions
Bit
Name
7
TF1
Function
Timer 1 Overflow Flag.
Set to 1 by hardware when Timer 1 overflows. This flag can be cleared by software but is
automatically cleared when the CPU vectors to the Timer 1 interrupt service routine.
6
TR1
Timer 1 Run Control.
Timer 1 is enabled by setting this bit to 1.
5
TF0
Timer 0 Overflow Flag.
Set to 1 by hardware when Timer 0 overflows. This flag can be cleared by software but is
automatically cleared when the CPU vectors to the Timer 0 interrupt service routine.
4
TR0
Timer 0 Run Control.
Timer 0 is enabled by setting this bit to 1.
3
IE1
External Interrupt 1.
This flag is set by hardware when an edge/level of type defined by IT1 is detected. It can
be cleared by software but is automatically cleared when the CPU vectors to the External
Interrupt 1 service routine in edge-triggered mode.
2
IT1
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 register IT01CF.
0: INT1 is level triggered.
1: INT1 is edge triggered.
1
IE0
External Interrupt 0.
This flag is set by hardware when an edge/level of type defined by IT0 is detected. It can
be cleared by software but is automatically cleared when the CPU vectors to the External
Interrupt 0 service routine in edge-triggered mode.
0
IT0
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.
0: INT0 is level triggered.
1: INT0 is edge triggered.
262
Preliminary Rev 0.6
Register 25.3. TMOD: Timer 0/1 Mode
Bit
7
6
Name
GATE1
CT1
Type
RW
RW
Reset
0
0
5
4
3
2
T1M
GATE0
CT0
T0M
RW
RW
RW
RW
0
0
0
0
1
0
0
0
SFR Address: 0x89
Table 25.5. TMOD Register Bit Descriptions
Bit
Name
7
GATE1
Function
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 defined by bit IN1PL in register IT01CF.
6
CT1
Counter/Timer 1 Select.
0: Timer Mode. Timer 1 increments on the clock defined by T1M in the CKCON register.
1: Counter Mode. Timer 1 increments on high-to-low transitions of an external pin (T1).
5:4
T1M
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-Reload
11: Mode 3, Timer 1 Inactive
3
GATE0
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 defined by bit IN0PL in register IT01CF.
2
CT0
Counter/Timer 0 Select.
0: Timer Mode. Timer 0 increments on the clock defined by T0M in the CKCON register.
1: Counter Mode. Timer 0 increments on high-to-low transitions of an external pin (T0).
1:0
T0M
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-Reload
11: Mode 3, Two 8-bit Counter/Timers
Preliminary Rev 0.6
263
Timers (Timer0, Timer1, Timer2 and Timer3)
C8051F85x/86x
Timers (Timer0, Timer1, Timer2 and Timer3)
C8051F85x/86x
Register 25.4. TL0: Timer 0 Low Byte
Bit
7
6
5
4
Name
TL0
Type
RW
Reset
0
0
0
0
3
2
1
0
0
0
0
0
SFR Address: 0x8A
Table 25.6. TL0 Register Bit Descriptions
Bit
Name
7:0
TL0
Function
Timer 0 Low Byte.
The TL0 register is the low byte of the 16-bit Timer 0.
264
Preliminary Rev 0.6
Register 25.5. TL1: Timer 1 Low Byte
Bit
7
6
5
4
Name
TL1
Type
RW
Reset
0
0
0
0
3
2
1
0
0
0
0
0
SFR Address: 0x8B
Table 25.7. TL1 Register Bit Descriptions
Bit
Name
7:0
TL1
Function
Timer 1 Low Byte.
The TL1 register is the low byte of the 16-bit Timer 1.
Preliminary Rev 0.6
265
Timers (Timer0, Timer1, Timer2 and Timer3)
C8051F85x/86x
Timers (Timer0, Timer1, Timer2 and Timer3)
C8051F85x/86x
Register 25.6. TH0: Timer 0 High Byte
Bit
7
6
5
4
Name
TH0
Type
RW
Reset
0
0
0
0
3
2
1
0
0
0
0
0
SFR Address: 0x8C
Table 25.8. TH0 Register Bit Descriptions
Bit
Name
7:0
TH0
Function
Timer 0 High Byte.
The TH0 register is the high byte of the 16-bit Timer 0.
266
Preliminary Rev 0.6
Register 25.7. TH1: Timer 1 High Byte
Bit
7
6
5
4
Name
TH1
Type
RW
Reset
0
0
0
0
3
2
1
0
0
0
0
0
SFR Address: 0x8D
Table 25.9. TH1 Register Bit Descriptions
Bit
Name
7:0
TH1
Function
Timer 1 High Byte.
The TH1 register is the high byte of the 16-bit Timer 1.
Preliminary Rev 0.6
267
Timers (Timer0, Timer1, Timer2 and Timer3)
C8051F85x/86x
Timers (Timer0, Timer1, Timer2 and Timer3)
C8051F85x/86x
Register 25.8. TMR2CN: Timer 2 Control
Bit
7
6
5
4
3
2
1
0
Name
TF2H
TF2L
TF2LEN
TF2CEN
T2SPLIT
TR2
Reserved
T2XCLK
Type
RW
RW
RW
RW
RW
RW
R
RW
Reset
0
0
0
0
0
0
0
0
SFR Address: 0xC8 (bit-addressable)
Table 25.10. TMR2CN Register Bit Descriptions
Bit
Name
7
TF2H
Function
Timer 2 High Byte Overflow Flag.
Set by hardware when the Timer 2 high byte overflows from 0xFF to 0x00. In 16 bit
mode, this will occur when Timer 2 overflows from 0xFFFF to 0x0000. When the Timer 2
interrupt is enabled, setting this bit causes the CPU to vector to the Timer 2 interrupt service routine. This bit is not automatically 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
TF2CEN
Timer 2 Capture Enable.
When set to 1, this bit enables Timer 2 Capture Mode. If TF2CEN is set and Timer 2
interrupts are enabled, an interrupt will be generated on a falling edge of the selected T2
input pin, and the current 16-bit timer value in TMR2H:TMR2L will be copied to
TMR2RLH:TMR2RLL.
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.
2
TR2
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 mode.
1
Reserved
Must write reset value.
0
T2XCLK
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 either 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).
268
Preliminary Rev 0.6
Register 25.9. TMR2RLL: Timer 2 Reload Low Byte
Bit
7
6
5
4
Name
TMR2RLL
Type
RW
Reset
0
0
0
0
3
2
1
0
0
0
0
0
SFR Address: 0xCA
Table 25.11. TMR2RLL Register Bit Descriptions
Bit
Name
7:0
TMR2RLL
Function
Timer 2 Reload Low Byte.
When operating in one of the auto-reload modes, TMR2RLL holds the reload value for
the low byte of Timer 2 (TMR2L). When oeprating in capture mode, TMR2RLL is the captured value of TMR2L.
Preliminary Rev 0.6
269
Timers (Timer0, Timer1, Timer2 and Timer3)
C8051F85x/86x
Timers (Timer0, Timer1, Timer2 and Timer3)
C8051F85x/86x
Register 25.10. TMR2RLH: Timer 2 Reload High Byte
Bit
7
6
5
4
Name
TMR2RLH
Type
RW
Reset
0
0
0
0
3
2
1
0
0
0
0
0
SFR Address: 0xCB
Table 25.12. TMR2RLH Register Bit Descriptions
Bit
Name
7:0
TMR2RLH
Function
Timer 2 Reload High Byte.
When operating in one of the auto-reload modes, TMR2RLH holds the reload value for
the high byte of Timer 2 (TMR2H). When oeprating in capture mode, TMR2RLH is the
captured value of TMR2H.
270
Preliminary Rev 0.6
Register 25.11. TMR2L: Timer 2 Low Byte
Bit
7
6
5
4
Name
TMR2L
Type
RW
Reset
0
0
0
0
3
2
1
0
0
0
0
0
SFR Address: 0xCC
Table 25.13. TMR2L Register Bit Descriptions
Bit
Name
7:0
TMR2L
Function
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.
Preliminary Rev 0.6
271
Timers (Timer0, Timer1, Timer2 and Timer3)
C8051F85x/86x
Timers (Timer0, Timer1, Timer2 and Timer3)
C8051F85x/86x
Register 25.12. TMR2H: Timer 2 High Byte
Bit
7
6
5
4
Name
TMR2H
Type
RW
Reset
0
0
0
0
3
2
1
0
0
0
0
0
SFR Address: 0xCD
Table 25.14. TMR2H Register Bit Descriptions
Bit
Name
7:0
TMR2H
Function
Timer 2 High Byte.
In 16-bit mode, the TMR2H register contains the high byte of the 16-bit Timer 2. In 8-bit
mode, TMR2H contains the 8-bit high byte timer value.
272
Preliminary Rev 0.6
Register 25.13. TMR3CN: Timer 3 Control
Bit
7
6
5
4
3
2
1
0
Name
TF3H
TF3L
TF3LEN
TF3CEN
T3SPLIT
TR3
Reserved
T3XCLK
Type
RW
RW
RW
RW
RW
RW
R
RW
Reset
0
0
0
0
0
0
0
0
SFR Address: 0x91
Table 25.15. TMR3CN Register Bit Descriptions
Bit
Name
7
TF3H
Function
Timer 3 High Byte Overflow Flag.
Set by hardware when the Timer 3 high byte overflows from 0xFF to 0x00. In 16 bit
mode, this will occur when Timer 3 overflows from 0xFFFF to 0x0000. When the Timer 3
interrupt is enabled, setting this bit causes the CPU to vector to the Timer 3 interrupt service routine. This bit is not automatically cleared by hardware.
6
TF3L
Timer 3 Low Byte Overflow Flag.
Set by hardware when the Timer 3 low byte overflows from 0xFF to 0x00. TF3L will be
set when the low byte overflows regardless of the Timer 3 mode. This bit is not automatically cleared by hardware.
5
TF3LEN
Timer 3 Low Byte Interrupt Enable.
When set to 1, this bit enables Timer 3 Low Byte interrupts. If Timer 3 interrupts are also
enabled, an interrupt will be generated when the low byte of Timer 3 overflows.
4
TF3CEN
Timer 3 Capture Enable.
When set to 1, this bit enables Timer 3 Capture Mode. If TF3CEN is set and Timer 3
interrupts are enabled, an interrupt will be generated on a falling edge of the low-frequency oscillator output, and the current 16-bit timer value in TMR3H:TMR3L will be copied to TMR3RLH:TMR3RLL.
3
T3SPLIT
Timer 3 Split Mode Enable.
When this bit is set, Timer 3 operates as two 8-bit timers with auto-reload.
0: Timer 3 operates in 16-bit auto-reload mode.
1: Timer 3 operates as two 8-bit auto-reload timers.
2
TR3
Timer 3 Run Control.
Timer 3 is enabled by setting this bit to 1. In 8-bit mode, this bit enables/disables TMR3H
only; TMR3L is always enabled in split mode.
1
Reserved
Must write reset value.
0
T3XCLK
Timer 3 External Clock Select.
This bit selects the external clock source for Timer 3. If Timer 3 is in 8-bit mode, this bit
selects the external oscillator clock source for both timer bytes. However, the Timer 3
Clock Select bits (T3MH and T3ML in register CKCON) may still be used to select
between the external clock and the system clock for either timer.
0: Timer 3 clock is the system clock divided by 12.
1: Timer 3 clock is the external clock divided by 8 (synchronized with SYSCLK).
Preliminary Rev 0.6
273
Timers (Timer0, Timer1, Timer2 and Timer3)
C8051F85x/86x
Timers (Timer0, Timer1, Timer2 and Timer3)
C8051F85x/86x
Register 25.14. TMR3RLL: Timer 3 Reload Low Byte
Bit
7
6
5
4
Name
TMR3RLL
Type
RW
Reset
0
0
0
0
3
2
1
0
0
0
0
0
SFR Address: 0x92
Table 25.16. TMR3RLL Register Bit Descriptions
Bit
Name
7:0
TMR3RLL
Function
Timer 3 Reload Low Byte.
When operating in one of the auto-reload modes, TMR3RLL holds the reload value for
the low byte of Timer 3 (TMR3L). When oeprating in capture mode, TMR3RLL is the captured value of TMR3L.
274
Preliminary Rev 0.6
Register 25.15. TMR3RLH: Timer 3 Reload High Byte
Bit
7
6
5
4
Name
TMR3RLH
Type
RW
Reset
0
0
0
0
3
2
1
0
0
0
0
0
SFR Address: 0x93
Table 25.17. TMR3RLH Register Bit Descriptions
Bit
Name
7:0
TMR3RLH
Function
Timer 3 Reload High Byte.
When operating in one of the auto-reload modes, TMR3RLH holds the reload value for
the high byte of Timer 3 (TMR3H). When oeprating in capture mode, TMR3RLH is the
captured value of TMR3H.
Preliminary Rev 0.6
275
Timers (Timer0, Timer1, Timer2 and Timer3)
C8051F85x/86x
Timers (Timer0, Timer1, Timer2 and Timer3)
C8051F85x/86x
Register 25.16. TMR3L: Timer 3 Low Byte
Bit
7
6
5
4
Name
TMR3L
Type
RW
Reset
0
0
0
0
3
2
1
0
0
0
0
0
SFR Address: 0x94
Table 25.18. TMR3L Register Bit Descriptions
Bit
Name
7:0
TMR3L
Function
Timer 3 Low Byte.
In 16-bit mode, the TMR3L register contains the low byte of the 16-bit Timer 3. In 8-bit
mode, TMR3L contains the 8-bit low byte timer value.
276
Preliminary Rev 0.6
Register 25.17. TMR3H: Timer 3 High Byte
Bit
7
6
5
4
Name
TMR3H
Type
RW
Reset
0
0
0
0
3
2
1
0
0
0
0
0
SFR Address: 0x95
Table 25.19. TMR3H Register Bit Descriptions
Bit
Name
7:0
TMR3H
Function
Timer 3 High Byte.
In 16-bit mode, the TMR3H register contains the high byte of the 16-bit Timer 3. In 8-bit
mode, TMR3H contains the 8-bit high byte timer value.
Preliminary Rev 0.6
277
Timers (Timer0, Timer1, Timer2 and Timer3)
C8051F85x/86x
Universal Asynchronous Receiver/Transmitter (UART0)
C8051F85x/86x
26. Universal Asynchronous Receiver/Transmitter (UART0)
UART0 is an asynchronous, full duplex serial port offering modes 1 and 3 of the standard 8051 UART. Enhanced
baud rate support allows a wide range of clock sources to generate standard baud rates (details in Section
“26.1. Enhanced Baud Rate Generation” on page 278). Received data buffering allows UART0 to start reception of
a second incoming data byte before software has finished reading the previous data byte.
UART0 has two associated SFRs: Serial Control Register 0 (SCON0) and Serial Data Buffer 0 (SBUF0). The
single SBUF0 location provides access to both transmit and receive registers. Writes to SBUF0 always access
the transmit register. Reads of SBUF0 always access the buffered receive register; it is not possible to
read data from the transmit register.
With UART0 interrupts enabled, an interrupt is generated each time a transmit is completed (TI is set in SCON0),
or a data byte has been received (RI is set in SCON0). The UART0 interrupt flags are not cleared by hardware
when the CPU vectors to the interrupt service routine. They must be cleared manually by software, allowing software to determine the cause of the UART0 interrupt (transmit complete or receive complete).
U A R T0
TI, R I
Interrupts
TB8
(9 th bit)
O utput Shift
R egister
Control /
C onfiguration
Baud R ate
G enerator
(Tim er 1)
TX
SB UF (8 LSBs)
TX C lk
R X C lk
Input Shift
R egister
R B8
(9 th bit)
RX
STAR T
D etection
Figure 26.1. UART0 Block Diagram
26.1. 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 26.2), 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.
278
Preliminary Rev 0.6
Baud Rate Generator
(In Timer 1)
TL1
START
Detection
2
TX Clock
2
RX Clock
TH1
RX Timer
Figure 26.2. UART0 Baud Rate Logic
Timer 1 should be configured for Mode 2, 8-bit auto-reload. 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, SYSCLK/48, the external oscillator clock/8, or an external input
T1. For any given Timer 1 overflow rate, the UART0 baud rate is determined by Equation 26.1.
1
UartBaudRate = ---  T1_Overflow_Rate
2
Equation 26.1. UART0 Baud Rate
Timer 1 overflow rate is selected as described in the Timer section. A quick reference for typical baud rates and
system clock frequencies is given in Table 26.1.
Preliminary Rev 0.6
279
Universal Asynchronous Receiver/Transmitter (UART0)
C8051F85x/86x
Universal Asynchronous Receiver/Transmitter (UART0)
C8051F85x/86x
26.2. Operational Modes
UART0 provides standard asynchronous, full duplex communication. The UART mode (8-bit or 9-bit) is selected by
the S0MODE bit in register SCON.
26.2.1. 8-Bit UART
8-Bit UART mode uses a total of 10 bits per data byte: one start bit, eight data bits (LSB first), and one stop bit.
Data are transmitted LSB first from the TX pin and received at the RX pin. On receive, the eight data bits are stored
in SBUF0 and the stop bit goes into RB8 in the SCON register.
Data transmission begins when software writes a data byte to the SBUF0 register. The TI Transmit Interrupt Flag is
set at the end of the transmission (the beginning of the stop-bit time). Data reception can begin any time after the
REN Receive Enable bit 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: RI must be logic 0, and if MCE is logic 1, the stop bit must be
logic 1. In the event of a receive data overrun, the first received 8 bits are latched into the SBUF0 receive register
and the following overrun data bits are lost.
If these conditions are met, the eight bits of data is stored in SBUF0, the stop bit is stored in RB8 and the RI flag is
set. If these conditions are not met, SBUF0 and RB8 will not be loaded and the RI flag will not be set. An interrupt
will occur if enabled when either TI or RI is set.
MARK
SPACE
START
BIT
D0
D1
D2
D3
D4
D5
BIT TIMES
BIT SAMPLING
Figure 26.3. 8-Bit UART Timing Diagram
280
Preliminary Rev 0.6
D6
D7
STOP
BIT
26.2.2. 9-Bit UART
9-bit UART mode uses a total of eleven bits per data byte: a start bit, 8 data bits (LSB first), a programmable ninth
data bit, and a stop bit. The state of the ninth transmit data bit is determined by the value in TB8, 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 RB8 and the stop bit is ignored.
Data transmission begins when an instruction writes a data byte to the SBUF0 register. The TI Transmit Interrupt
Flag is set at the end of the transmission (the beginning of the stop-bit time). Data reception can begin any time
after the REN Receive Enable bit 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) RI must be logic 0, and (2) if MCE is logic 1, the 9th
bit must be logic 1 (when MCE 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 RB8, and the RI flag is set to 1. If the above
conditions are not met, SBUF0 and RB8 will not be loaded and the RI flag will not be set to 1. A UART0 interrupt
will occur if enabled when either TI or RI is set to 1.
MARK
SPACE
START
BIT
D0
D1
D2
D3
D4
D5
D6
D7
D8
STOP
BIT
BIT TIMES
BIT SAMPLING
Figure 26.4. 9-Bit UART Timing Diagram
Preliminary Rev 0.6
281
Universal Asynchronous Receiver/Transmitter (UART0)
C8051F85x/86x
Universal Asynchronous Receiver/Transmitter (UART0)
C8051F85x/86x
26.3. Multiprocessor Communications
9-Bit UART mode supports multiprocessor communication between a master processor and one or more slave
processors by special use of the ninth data bit. When a master processor wants to transmit to one or more slaves,
it first sends an address byte to select the target(s). An address byte differs from a data byte in that its ninth bit is
logic 1; in a data byte, the ninth bit is always set to logic 0.
Setting the MCE bit 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 (RB8 = 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 MCE bit to enable interrupts on the reception of the following data
byte(s). Slaves that weren't addressed leave their MCE 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 MCE bit to ignore all transmissions until it receives the next address byte.
Multiple addresses can be assigned to a single slave and/or a single address can be assigned to multiple slaves,
thereby enabling "broadcast" transmissions to more than one slave simultaneously. The master processor can be
configured to receive all transmissions or a protocol can be implemented such that the master/slave role is
temporarily reversed to enable half-duplex transmission between the original master and slave(s).
Master
Device
RX
TX
Slave
Device
RX
TX
Slave
Device
RX
TX
Slave
Device
RX
TX
Figure 26.5. UART Multi-Processor Mode Interconnect Diagram
282
Preliminary Rev 0.6
V+
Table 26.1. Timer Settings for Standard Baud Rates Using The Internal 24.5 MHz Oscillator
Internal Osc.
SYSCLK from
Frequency: 49 MHz
Oscillator Timer Clock
Source
Divide
Factor
SCA1–SCA0
(pre-scale
select)1
T1M1
Timer 1
Reload
Value (hex)
SYSCLK
XX2
1
0xCB
212
SYSCLK
XX
1
0x96
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
Target
Baud Rate
(bps)
Baud Rate
% Error
230400
–0.32%
106
115200
–0.32%
57600
Notes:
1. SCA1–SCA0 and T1M bit definitions can be found in Timer1 chapter.
2. X = Don’t care.
Preliminary Rev 0.6
283
Universal Asynchronous Receiver/Transmitter (UART0)
C8051F85x/86x
Universal Asynchronous Receiver/Transmitter (UART0)
C8051F85x/86x
26.4. UART Control Registers
Register 26.1. SCON0: UART0 Serial Port Control
Bit
7
6
5
4
3
2
1
0
Name
SMODE
Reserved
MCE
REN
TB8
RB8
TI
RI
Type
RW
R
RW
RW
RW
RW
RW
RW
Reset
0
1
0
0
0
0
0
0
SFR Address: 0x98 (bit-addressable)
Table 26.2. SCON0 Register Bit Descriptions
Bit
Name
7
SMODE
Function
Serial Port 0 Operation Mode.
Selects the UART0 Operation Mode.
0: 8-bit UART with Variable Baud Rate (Mode 0).
1: 9-bit UART with Variable Baud Rate (Mode 1).
6
Reserved
5
MCE
Must write reset value.
Multiprocessor Communication Enable.
This bit enables checking of the stop bit or the 9th bit in multi-drop communication buses.
The function of this bit is dependent on the UART0 operation mode selected by the
SMODE bit. In Mode 0 (8-bits), the peripheral will check that the stop bit is logic 1. In
Mode 1 (9-bits) the peripheral will check for a logic 1 on the 9th bit.
0: Ignore level of 9th bit / Stop bit.
1: RI is set and an interrupt is generated only when the stop bit is logic 1 (Mode 0) or
when the 9th bit is logic 1 (Mode 1).
4
REN
Receive Enable.
0: UART0 reception disabled.
1: UART0 reception enabled.
3
TB8
Ninth Transmission Bit.
The logic level of this bit will be sent as the ninth transmission bit in 9-bit UART Mode
(Mode 1). Unused in 8-bit mode (Mode 0).
2
RB8
Ninth Receive Bit.
RB8 is assigned the value of the STOP bit in Mode 0; it is assigned the value of the 9th
data bit in Mode 1.
1
TI
Transmit Interrupt Flag.
Set by hardware when a byte of data has been transmitted by UART0 (after the 8th bit in
8-bit UART Mode, or at the beginning of the STOP bit in 9-bit UART Mode). When the
UART0 interrupt is enabled, setting this bit causes the CPU to vector to the UART0 interrupt service routine. This bit must be cleared manually by software.
284
Preliminary Rev 0.6
Table 26.2. SCON0 Register Bit Descriptions
Bit
Name
0
RI
Function
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.
Preliminary Rev 0.6
285
Universal Asynchronous Receiver/Transmitter (UART0)
C8051F85x/86x
Universal Asynchronous Receiver/Transmitter (UART0)
C8051F85x/86x
Register 26.2. SBUF0: UART0 Serial Port Data Buffer
Bit
7
6
5
4
Name
SBUF0
Type
RW
Reset
0
0
0
0
3
2
1
0
0
0
0
0
SFR Address: 0x99
Table 26.3. SBUF0 Register Bit Descriptions
Bit
Name
7:0
SBUF0
Function
Serial Data Buffer Bits.
This SFR accesses two registers; a transmit shift register and a receive latch register.
When data is written to SBUF0, it goes to the transmit shift register and is held for serial
transmission. Writing a byte to SBUF0 initiates the transmission. A read of SBUF0
returns the contents of the receive latch.
286
Preliminary Rev 0.6
Watchdog Timer (WDT0)
C8051F85x/86x
27. Watchdog Timer (WDT0)
The C8051F85x/86x family includes a programmable Watchdog Timer (WDT) running off the low-frequency
oscillator. A WDT overflow will force the MCU into the reset state. To prevent the reset, the WDT must be restarted
by application software before overflow. If the system experiences a software or hardware malfunction preventing
the software from restarting the WDT, the WDT will overflow and cause a reset.
Following a reset the WDT is automatically enabled and running with the default maximum time interval. If desired
the WDT can be disabled by system software or locked on to prevent accidental disabling. Once locked, the WDT
cannot be disabled until the next system reset. The state of the RST pin is unaffected by this reset.
The WDT consists of an internal timer running from the low-frequency oscillator. The timer measures the period
between specific writes to its control register. If this period exceeds the programmed limit, a WDT reset is
generated. The WDT can be enabled and disabled as needed in software, or can be permanently enabled if
desired. When the WDT is active, the low-frequency oscillator is forced on. All watchdog features are controlled via
the Watchdog Timer Control Register (WDTCN).
Watchdog Timer
Lock and Key
Watchdog Timer
LFOSC0
Timeout Interval
Watchdog
Reset
Figure 27.1. Watchdog Timer Block Diagram
288
Preliminary Rev 0.6
27.1. Enabling / Resetting the WDT
The watchdog timer is both enabled and reset by writing 0xA5 to the WDTCN register. The user's application
software should include periodic writes of 0xA5 to WDTCN as needed to prevent a watchdog timer overflow. The
WDT is enabled and reset as a result of any system reset.
27.2. Disabling the WDT
Writing 0xDE followed by 0xAD to the WDTCN register disables the WDT. The following code segment illustrates
disabling the WDT:
CLR EA
MOV WDTCN,#0DEh
MOV WDTCN,#0ADh
SETB EA
; disable all interrupts
; disable software watchdog timer
; re-enable interrupts
The writes of 0xDE and 0xAD must occur within 4 clock cycles of each other, or the disable operation is ignored.
Interrupts should be disabled during this procedure to avoid delay between the two writes.
27.3. Disabling the WDT Lockout
Writing 0xFF to WDTCN locks out the disable feature. Once locked out, the disable operation is ignored until the
next system reset. Writing 0xFF does not enable or reset the watchdog timer. Applications always intending to use
the watchdog should write 0xFF to WDTCN in the initialization code.
27.4. Setting the WDT Interval
WDTCN.[2:0] controls the watchdog timeout interval. The interval is given by the following equation, where Tlfosc is
the low-frequency oscillator clock period:
T LFOSC  4  WDTCN[2:0] + 3 
This provides a nominal interval range of 0.8 ms to 13.1 s. WDTCN.7 must be logic 0 when setting this interval.
Reading WDTCN returns the programmed interval. WDTCN.[2:0] reads 111b after a system reset.
Preliminary Rev 0.6
289
Watchdog Timer (WDT0)
C8051F85x/86x
Watchdog Timer (WDT0)
C8051F85x/86x
27.5. Watchdog Timer Control Registers
Register 27.1. WDTCN: Watchdog Timer Control
Bit
7
6
5
4
Name
WDTCN
Type
RW
Reset
0
0
0
1
3
2
1
0
0
1
1
1
SFR Address: 0x97
Table 27.1. WDTCN Register Bit Descriptions
Bit
Name
7:0
WDTCN
Function
WDT Control.
The WDT control field has different behavior for reads and writes.
Read:
When reading the WDTCN register, the lower three bits (WDTCN[2:0]) indicate the current timeout interval. Bit WDTCN.4 indicates whether the WDT is active (logic 1) or inactive (logic 0).
Write:
Writing the WDTCN register can set the timeout interval, enable the WDT, disable the
WDT, reset the WDT, or lock the WDT to prevent disabling.
Writing to WDTCN with the MSB (WDTCN.7) cleared to 0 will set the timeout interval to
the value in bits WDTCN[2:0].
Writing 0xA5 both enables and reloads the WDT.
Writing 0xDE followed within 4 system clocks by 0xAD disables the WDT.
Writing 0xFF locks out the disable feature until the next device reset.
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C2 Interface
C8051F85x/86x
28. C2 Interface
C8051F85x/86x devices include an on-chip Silicon Labs 2-Wire (C2) debug interface to allow flash programming
and in-system debugging with the production part installed in the end application. The C2 interface uses a clock
signal (C2CK) and a bi-directional C2 data signal (C2D) to transfer information between the device and a host
system. Details on the C2 protocol can be found in the C2 Interface Specification.
28.1. C2 Pin Sharing
The C2 protocol allows the C2 pins to be shared with user functions so that in-system debugging and flash
programming may be performed. C2CK is shared with the RST pin, while the C2D signal is shared with a port I/O
pin. This is possible because C2 communication is typically performed when the device is in the halt state, where
all on-chip peripherals and user software are stalled. In this halted state, the C2 interface can safely ‘borrow’ the
C2CK and C2D pins. In most applications, external resistors are required to isolate C2 interface traffic from the
user application. A typical isolation configuration is shown in Figure 28.1.
C8051Fxxx
/Reset (a)
C2CK
Input (b)
C2D
Output (c)
C2 Interface Master
Figure 28.1. Typical C2 Pin Sharing
The configuration in Figure 28.1 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.
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28.2. C2 Interface Registers
The following describes the C2 registers necessary to perform flash programming through the C2 interface. All C2
registers are accessed through the C2 interface, and are not available in the SFR map for firmware access.
Register 28.1. C2ADD: C2 Address
Bit
7
6
5
4
Name
C2ADD
Type
RW
Reset
0
0
0
0
3
2
1
0
0
0
0
0
This register is part of the C2 protocol.
Table 28.1. C2ADD Register Bit Descriptions
Bit
Name
7:0
C2ADD
Function
C2 Address.
The C2ADD register is accessed via the C2 interface. The value written to C2ADD
selects the target data register for C2 Data Read and Data Write commands.
0x00: C2DEVID
0x01: C2REVID
0x02: C2FPCTL
0xB4: C2FPDAT
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C8051F85x/86x
Register 28.2. C2DEVID: C2 Device ID
Bit
7
6
5
4
Name
C2DEVID
Type
R
Reset
0
0
1
1
3
2
1
0
0
0
0
0
C2 Address: 0x00
Table 28.2. C2DEVID Register Bit Descriptions
Bit
Name
7:0
C2DEVID
Function
Device ID.
This read-only register returns the 8-bit device ID: 0x30 (C8051F85x/86x).
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Preliminary Rev 0.6
Register 28.3. C2REVID: C2 Revision ID
Bit
7
6
5
4
Name
C2REVID
Type
R
Reset
X
X
X
X
3
2
1
0
X
X
X
X
C2 Address: 0x01
Table 28.3. C2REVID Register Bit Descriptions
Bit
Name
7:0
C2REVID
Function
Revision ID.
This read-only register returns the 8-bit revision ID. For example: 0x00 = Revision A,
0x01 = Revision B and 0x02 = Revision C.
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C2 Interface
C8051F85x/86x
Register 28.4. C2FPCTL: C2 Flash Programming Control
Bit
7
6
5
4
Name
C2FPCTL
Type
RW
Reset
0
0
0
0
3
2
1
0
0
0
0
0
C2 Address: 0x02
Table 28.4. C2FPCTL Register Bit Descriptions
Bit
Name
7:0
C2FPCTL
Function
Flash Programming Control Register.
This register is used to enable flash programming via the C2 interface. To enable C2
flash programming, the following codes must be written in order: 0x02, 0x01. Note that
once C2 flash programming is enabled, a system reset must be issued to resume normal
operation.
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Preliminary Rev 0.6
Register 28.5. C2FPDAT: C2 Flash Programming Data
Bit
7
6
5
4
Name
C2FPDAT
Type
RW
Reset
0
0
0
0
3
2
1
0
0
0
0
0
C2 Address: 0xB4
Table 28.5. C2FPDAT Register Bit Descriptions
Bit
Name
7:0
C2FPDAT
Function
C2 Flash Programming Data Register.
This register is used to pass flash commands, addresses, and data during C2 flash
accesses. Valid commands are listed below.
0x03: Device Erase
0x06: Flash Block Read
0x07: Flash Block Write
0x08: Flash Page Erase
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C8051F85x/86x
C8051F85x/86x
DOCUMENT CHANGE LIST
Revision 0.5 to Revision 0.6










Updated front page block diagram.
Updated ADC supply current parameters in Table 1.2, “Power Consumption,” on page 7.
Corrected flash programming voltage range in "Table 1.4. Flash Memory" on page 10.
Added ADC Power-On Time specification in Table 1.7, “ADC,” on page 12.
Added section "1.2. Typical Power Curves" on page 17.
Corrected DERIVID Information in "Table 11.2. DERIVID Register Bit Descriptions" on page 63.
Updated ADC chapter ("14. Analog-to-Digital Converter (ADC0)" on page 78) and expanded section "14.5.
Power Considerations" on page 84 with recommended power configuration settings.
Updated Figure 21.1, “Port I/O Functional Block Diagram,” on page 178.
Corrected reset value in Register 24.5, “SMB0ADM: SMBus0 Slave Address Mask,” on page 250.
Corrected description of IE0 in "Table 25.4. TCON Register Bit Descriptions" on page 262.
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CONTACT INFORMATION
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Austin, TX 78701
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and register to submit a technical support request.
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