Philips P80C31X2, P80C32X2, P80C51X2, P80C52X2, P80C54X2 User Manual

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INTEGRATED CIRCUITS

P80C31X2/32X2 P80C51X2/52X2/54X2/58X2 P87C51X2/52X2/54X2/58X2

80C51 8-bit microcontroller family

4K/8K/16K/32K ROM/OTP 128B/256B RAM low voltage (2.7 to 5.5 V), low power, high speed (30/33 MHz)

Product data Supersedes data of 2002 Sep 12

2003 Jan 24

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Philips Semiconductors Product data

80C51 8-bit microcontroller family

4K/8K/16K/32K ROM/OTP, low voltage (2.7 to 5.5 V), low power, high speed (30/33 MHz)

DESCRIPTION

The Philips microcontrollers described in this data sheet are high-performance static 80C51 designs incorporating Philips’ high-density CMOS technology with operation from 2.7 V to 5.5 V . They support both 6-clock and 12-clock operation.

The P8xC31X2/51X2 and P8xC32X2/52X2/54X2/58X2 contain 128 byte RAM and 256 byte RAM respectively, 32 I/O lines, three 16-bit counter/timers, a six-source, four-priority level nested interrupt structure, a serial I/O port for either multi-processor communications, I/O expansion or full duplex UART, and on-chip oscillator and clock circuits.

selectable modes of power reduction — idle mode and power-down mode — are available. The idle mode freezes the CPU while allowing the RAM, timers, serial port, and interrupt system to continue functioning. The power-down mode saves the RAM contents but freezes the oscillator, causing all other chip functions to be inoperative. Since the design is static, the clock can be stopped without loss of user data. Then the execution can be resumed from the point the clock was stopped.

SELECTION TABLE

For applications requiring more ROM and RAM, as well as more on-chip peripherals, see the P89C66x and P89C51Rx2 data sheets.

P80C3xX2; P80C5xX2;

P87C5xX2

In addition, the devices are low power static designs which offer a wide range of operating frequencies down to zero. Two software

Type Memory Timers Serial Interfaces

Max.

Freq.

Range

at 6-clk

at 3V

/ 12-clk

RAM

ROM

OTP

P87C58X2 P80C58X2 P87C54X2 P80C54X2 P87C52X2 P80C52X2 P87C51X2 P80C51X2 P80C32X2 P80C31X2

NOTE:

C = Inter-Integrated Circuit Bus; CAN = Controller Area Network; SPI = Serial Peripheral Interface; PCA = Programmable Counter Array;

1. I

256B – 32K – 3 – – – 256B 32K – – 3 – – – 256B – 16K – 3 – – – 256B 16K – – 3 – – – 256B – 8K – 3 – – – 256B 8K – – 3 – – – 128B – 4K – 3 – – – 128B 4K – – 3 – – – 256B – – – 3 – – – 128B – – – 3 – – –

Flash

# of Timers

PWM

PCA

UART

CAN

SPI

ADC bits/ch.

I/O Pins

Interrupts

(External)

Program

Security

Default Clock

Rate

Optional

– – – – 32 6 (2)

– – – – 32 6 (2) – 12–clk 6-clk 30/33 0–16 0–30/33

12–clk 6-clk 30/33 0–16 0–30/33

Clock Rate

(MHz)

ADC = Analog-to-Digital Converter; PWM = Pulse Width Modulation

Freq. Range at 5V (MHz)

2003 Jan 24 853-2337 29260

Philips Semiconductors Product data

80C51 8-bit microcontroller family

4K/8K/16K/32K ROM/OTP, low voltage (2.7 to 5.5 V), low power, high speed (30/33 MHz)

FEATURES

•80C51 Central Processing Unit

– 4 kbytes ROM/EPROM (P80/P87C51X2) – 8 kbytes ROM/EPROM (P80/P87C52X2) – 16 kbytes ROM/EPROM (P80/P87C54X2) – 32 kbytes ROM/EPROM (P80/P87C58X2) – 128 byte RAM (P80/P87C51X2 and P80C31X2) – 256 byte RAM (P80/P87C52/54X2/58X2 and P80C32X2) – Boolean processor – Fully static operation – Low voltage (2.7 V to 5.5 V at 16 MHz) operation

•12-clock operation with selectable 6-clock operation (via software

or via parallel programmer)

•Memory addressing capability

– Up to 64 kbytes ROM and 64 kbytes RAM

•Power control modes:

– Clock can be stopped and resumed – Idle mode – Power-down mode

•CMOS and TTL compatible

•Two speed ranges at V

– 0 to 30 MHz with 6-clock operation – 0 to 33 MHz with 12-clock operation

= 5 V

P80C3xX2; P80C5xX2;

P87C5xX2

•PLCC, DIP, TSSOP or LQFP packages

•Extended temperature ranges

•Dual Data Pointers

•Security bits:

– ROM (2 bits) – OTP (3 bits)

•Encryption array - 64 bytes

•Four interrupt priority levels

•Six interrupt sources

•Four 8-bit I/O ports

•Full-duplex enhanced UART

– Framing error detection – Automatic address recognition

•Three 16-bit timers/counters T0, T1 (standard 80C51) and

additional T2 (capture and compare)

•Programmable clock-out pin

•Asynchronous port reset

•Low EMI (inhibit ALE, slew rate controlled outputs, and 6-clock

mode)

•Wake-up from Power Down by an external interrupt.

2003 Jan 24

Philips Semiconductors Product data

80C51 8-bit microcontroller family

4K/8K/16K/32K ROM/OTP, low voltage (2.7 to 5.5 V), low power, high speed (30/33 MHz)

P80C3xX2; P80C5xX2;

P87C5xX2

P80C31/32X2 ORDERING INFORMATION (ROMLESS)

Type number Package Temperature

Name Description Version

P80C31X2BA PLCC44 plastic leaded chip carrier; 44 leads P80C31X2BN DIP40 plastic dual in-line package; 40 leads (600 mil) P80C32X2BA PLCC44 plastic leaded chip carrier; 44 leads P80C32X2BN DIP40 plastic dual in-line package; 40 leads (600 mil) P80C32X2BBD LQFP44 plastic low profile quad flat package; 44 leads; body 10 x 10 x 1.4 mm P80C32X2FA PLCC44 plastic leaded chip carrier; 44 leads P80C32X2FN DIP40 plastic dual in-line package; 40 leads (600 mil)

SOT187-2 0 to +70 SOT129-1 0 to +70 SOT187-2 0 to +70 SOT129-1 0 to +70 SOT389-1 0 to +70 SOT187-2 –40 to +85 SOT129-1 –40 to +85

Range (°C)

P87C51X2 ORDERING INFORMATION (4 KBYTE OTP)

Type number Package Temperature

Name Description Version

P87C51X2BA PLCC44 plastic leaded chip carrier; 44 leads SOT187-2 0 to +70 P87C51X2BN DIP40 plastic dual in-line package; 40 leads (600 mil) SOT129-1 0 to +70 P87C51X2BBD LQFP44 plastic low profile quad flat package; 44 leads; body 10 x 10 x 1.4 mm SOT389-1 0 to +70 P87C51X2FA PLCC44 plastic leaded chip carrier; 44 leads SOT187-2 –40 to +85 P87C51X2FBD LQFP44 plastic low profile quad flat package; 44 leads; body 10 x 10 x 1.4 mm SOT389-1 –40 to +85

Range (°C)

P87C52X2 ORDERING INFORMATION (8 KBYTE OTP)

Type number Package Temperature

Name Description Version

P87C52X2BA PLCC44 plastic leaded chip carrier; 44 leads SOT187-2 0 to +70 P87C52X2BN DIP40 plastic dual in-line package; 40 leads (600 mil) SOT129-1 0 to +70 P87C52X2BBD LQFP44 plastic low profile quad flat package; 44 leads; body 10 x 10 x 1.4 mm SOT389-1 0 to +70 P87C52X2FA PLCC44 plastic leaded chip carrier; 44 leads SOT187-2 –40 to +85 P87C52X2FN DIP40 plastic dual in-line package; 40 leads (600 mil) SOT129-1 –40 to +85 P87C52X2FBD LQFP44 plastic low profile quad flat package; 44 leads; body 10 x 10 x 1.4 mm SOT389-1 –40 to +85

Range (°C)

P87C54X2 ORDERING INFORMATION (16 KBYTE OTP)

Type number Package Temperature

Name Description Version

P87C54X2BA P87C54X2BN P87C54X2BBD LQFP44 plastic low profile quad flat package; 44 leads; body 10 x 10 x 1.4 mm SOT389-1 0 to +70 P87C54X2BDH TSSOP38 plastic thin shrink small outline package; 38 leads; body width 4.4 mm;

P87C54X2FA P87C54X2FBD LQFP44 plastic low profile quad flat package; 44 leads; body 10 x 10 x 1.4 mm SOT389-1 –40 to +85

PLCC44 DIP40

PLCC44

plastic lead chip carrier; 44 leads plastic dual in-line package; 40 leads (600 mil)

lead pitch 0.5 mm plastic lead chip carrier; 44 leads

SOT187-2 SOT129-1

SOT510-1 0 to +70

SOT187-2

Range (°C)

0 to +70 0 to +70

–40 to +85

P87C58X2 ORDERING INFORMATION (32 KBYTE OTP)

Type number Package Temperature

Name Description Version

P87C58X2BA P87C58X2BN P87C58X2BBD LQFP44 plastic low profile quad flat package; 44 leads; body 10 x 10 x 1.4 mm SOT389-1 0 to +70 P87C58X2FA P87C58X2FBD LQFP44 plastic low profile quad flat package; 44 leads; body 10 x 10 x 1.4 mm SOT389-1 –40 to +85 P87C58X2FN

All OTP parts listed here are also available as ROM parts (80C5xX2). Please contact your Philips representative if you would like to order a ROM part.

PLCC44 DIP40

PLCC44

DIP40

plastic lead chip carrier; 44 leads plastic dual in-line package; 40 leads (600 mil)

plastic lead chip carrier; 44 leads

plastic dual in-line package; 40 leads (600 mil)

SOT187-2 SOT129-1

SOT187-2

SOT129-1

Range (°C)

0 to +70 0 to +70

–40 to +85

2003 Jan 24

Philips Semiconductors Product data

80C51 8-bit microcontroller family

P80C3xX2; P80C5xX2;

4K/8K/16K/32K ROM/OTP, low voltage (2.7 to 5.5 V), low power, high speed (30/33 MHz)

P ART NUMBER DERIVATION

Memory Temperature Range Package

P87C51X2

7 = OTP 0 = ROM or

ROMless

The following table illustrates the correlation between operating mode, power supply and maximum external clock frequency:

Operating Mode

6-clock 5 V ± 10% 30 MHz 6-clock 2.7 V to 5.5 V 16 MHz 12-clock 5 V ± 10% 33 MHz 12-clock 2.7 V to 5.5 V 16 MHz

5 = ROM/OTP 3 = ROMless

1 = 128 BYTES RAM

4 KBYTES ROM/OTP

2 = 256 BYTES RAM

8 KBYTES ROM/OTP

4 = 256 BYTES RAM

16 KBYTES ROM/OTP

8 = 256 BYTES RAM

32 KBYTES ROM/OTP

Power Supply Maximum Clock Frequency

X2 = 6-clock mode available

B = 0 °C TO +70 °C F = –40 °C TO +85 °C

A = PLCC N = DIP BD = LQFP DH = TSSOP

P87C5xX2

2003 Jan 24

Philips Semiconductors Product data

80C51 8-bit microcontroller family

4K/8K/16K/32K ROM/OTP, low voltage (2.7 to 5.5 V), low power, high speed (30/33 MHz)

BLOCK DIAGRAM 1

Accelerated 80C51 CPU

(12-clk mode, 6-clk mode)

0K / 4K / 8K / 16K /

32 kbyte

CODE ROM / EPROM

128 / 256 Byte

Data RAM

Port 3

Configurable I/Os

P80C3xX2; P80C5xX2;

P87C5xX2

Full-duplex enhanced

UART

Timer 0 Timer 1

Timer 2

Resonator

Port 2

Configurable I/Os

Port 1

Configurable I/Os

Port 0

Configurable I/Os

OscillatorCrystal or

su01579

2003 Jan 24

Philips Semiconductors Product data

80C51 8-bit microcontroller family

4K/8K/16K/32K ROM/OTP, low voltage (2.7 to 5.5 V), low power, high speed (30/33 MHz)

BLOCK DIAGRAM 2 (CPU-ORIENTED)

P0.0–P0.7 P2.0–P2.7

PORT 0

DRIVERS

RAM ADDR

RAM

ACC

TMP2

PORT 0

LATCH

TMP1

PORT 2

DRIVERS

PORT 2

LATCH

P80C3xX2; P80C5xX2;

P87C5xX2

ROM/EPROM

STACK

POINTER

PROGRAM ADDRESS REGISTER

PSEN

ALE/PROG

EA / V

RST

TIMING

AND

CONTROL

OSCILLATOR

XTAL1 XTAL2

INSTRUCTION

NOTE:

1. P3.2 and P3.5 absent in the TSSOP38 package.

PSW

PORT 1

LATCH

PORT 1

DRIVERS

P1.0–P1.7

ALU

SFRs

TIMERS

PORT 3

LATCH

PORT 3

DRIVERS

P3.0–P3.7

BUFFER

INCRE-

MENTER

8 16

PROGRAM COUNTER

DPTR’S

MULTIPLE

su01723

2003 Jan 24

Philips Semiconductors Product data

80C51 8-bit microcontroller family

4K/8K/16K/32K ROM/OTP, low voltage (2.7 to 5.5 V), low power, high speed (30/33 MHz)

LOGIC SYMBOL

XTAL1

ADDRESS AND

PORT 0

XTAL2

RST

EA/V

ALE/PROG RxD TxD

INT0

INT1

SECONDARY FUNCTIONS

PSEN

PORT 3

PORT 1PORT 2

NOTE:

/P3.2 and T1/P3.5 are absent in the TSSOP38 package.

1. INT0

DATA BUS

T2 T2EX

ADDRESS BUS

SU01724

P80C3xX2; P80C5xX2;

PLASTIC DUAL IN-LINE PACKAGE PIN CONFIGURA TIONS

T2/P1.0

T2EX/P1.1

P1.2 P1.3 P1.4 P1.5 P1.6 P1.7

RST RxD/P3.0 TxD/P3.1

/P3.2

INT0

/P3.3

INT1

T0/P3.4 T1/P3.5

/P3.6

/P3.7

XTAL2 XTAL1

1 2 3 4 5 6 7 8

9 10 11 12 13 14 15 16 17 18 19 20

DUAL

IN-LINE

PACKAGE

40 39 38 37 36 35 34 33 32 31 30 29 28 27 26 25 24 23 22 21

P87C5xX2

P0.0/AD0 P0.1/AD1 P0.2/AD2 P0.3/AD3 P0.4/AD4 P0.5/AD5 P0.6/AD6 P0.7/AD7 EA

ALE PSEN P2.7/A15 P2.6/A14 P2.5/A13 P2.4/A12 P2.3/A11 P2.2/A10 P2.1/A9 P2.0/A8

SU01063

2003 Jan 24

Philips Semiconductors Product data

80C51 8-bit microcontroller family

4K/8K/16K/32K ROM/OTP, low voltage (2.7 to 5.5 V), low power, high speed (30/33 MHz)

PLASTIC LEADED CHIP CARRIER PIN FUNCTIONS

6140

Pin Function

1 NIC* 2 P1.0/T2 3 P1.1/T2EX 4 P1.2 5 P1.3 6 P1.4 7 P1.5 8 P1.6

9 P1.7 10 RST 11 P3.0/RxD 12 NIC* 13 P3.1/TxD 14 P3.2/INT0 15 P3.3/INT1

* NO INTERNAL CONNECTION

PLCC

18 28

Pin Function

16 P3.4/T0 17 P3.5/T1 18 P3.6/WR 19 P3.7/RD 20 XTAL2 21 XTAL1 22 V

23 NIC* 24 P2.0/A8 25 P2.1/A9 26 P2.2/A10 27 P2.3/A11 28 P2.4/A12 29 P2.5/A13 30 P2.6/A14

Pin Function

31 P2.7/A15 32 PSEN 33 ALE 34 NIC* 35 EA/V 36 P0.7/AD7 37 P0.6/AD6 38 P0.5/AD5 39 P0.4/AD4 40 P0.3/AD3 41 P0.2/AD2 42 P0.1/AD1 43 P0.0/AD0 44 V

SU01062

P80C3xX2; P80C5xX2;

P87C5xX2

PLASTIC THIN SHRINK SMALL OUTLINE PACK PIN FUNCTIONS

Pin Function

27 P0.1/AD1 28 P0.0/AD0 29 V

30 P1.0/T2 31 P1.1/T2EX 32 P1.2 33 P1.3 34 P1.4 35 P1.5 36 P1.6 37 P1.7 38 RST

su01725

Pin Function

1 P3.0/RxD 2 P3.1/TxD 3 P3.3/INT1 4 P3.4/T0 5 P3.6/WR 6 P3.7/RD 7 XTAL2 8 XTAL1 9V

10 P2.0/A8 11 P2.1/A9 12 P2.2/A10 13 P2.3/A11

TSSOP

19 20

Pin Function

14 P2.4/A12 15 P2.5/A13 16 P2.6/A14 17 P2.7/A15 18 PSEN 19 ALE/PROG 20 EA/V 21 P0.7/AD7 22 P0.6/AD6 23 P0.5/AD5 24 P0.4/AD4 25 P0.3/AD3 26 P0.2/AD2

LOW PROFILE QUAD FLAT PACK PIN FUNCTIONS

44 34

LQFP

12 22

Pin Function

1 P1.5 2 P1.6 3 P1.7 4 RST 5 P3.0/RxD 6 NIC* 7 P3.1/TxD 8 P3.2/INT0

9 P3.3/INT1 10 P3.4/T0 11 P3.5/T1 12 P3.6/WR 13 P3.7/RD 14 XTAL2 15 XTAL1

* NO INTERNAL CONNECTION

Pin Function

16 V

17 NIC* 18 P2.0/A8 19 P2.1/A9 20 P2.2/A10 21 P2.3/A11 22 P2.4/A12 23 P2.5/A13 24 P2.6/A14 25 P2.7/A15 26 PSEN 27 ALE 28 NIC*

29 EA 30 P0.7/AD7

Pin Function

31 P0.6/AD6 32 P0.5/AD5 33 P0.4/AD4 34 P0.3/AD3 35 P0.2/AD2 36 P0.1/AD1 37 P0.0/AD0 38 V

39 NIC* 40 P1.0/T2 41 P1.1/T2EX 42 P1.2 43 P1.3 44 P1.4

SU01487

2003 Jan 24

Philips Semiconductors Product data

80C51 8-bit microcontroller family

4K/8K/16K/32K ROM/OTP, low voltage (2.7 to 5.5 V), low power, high speed (30/33 MHz)

P80C3xX2; P80C5xX2;

P87C5xX2

PIN DESCRIPTIONS

PIN NUMBER

MNEMONIC DIP PLCC LQFP TSSOP TYPE NAME AND FUNCTION

P0.0-0.7 39–32 43–36 37–30 28–21 I/O Port 0: Port 0 is an open-drain, bidirectional I/O port. Port 0 pins that have 1s

P1.0–P1.7 1–8 2–9 40–44,

P2.0–P2.7 21–28 24–31 18–25 10–17 I/O Port 2: Port 2 is an 8-bit bidirectional I/O port with internal pull-ups. Port 2 pins that

P3.0–P3.7 10–17 11,

RST 9 10 4 38 I Reset: A high on this pin for two machine cycles while the oscillator is running,

ALE/PROG 30 33 27 19 O Address Latch Enable/Program Pulse: Output pulse for latching the low byte of

20 22 16 9 I Ground: 0 V reference. 40 44 38 29 I Power Supply: This is the power supply voltage for normal, idle, and power-down

30–37 I/O Port 1: Port 1 is an 8-bit bidirectional I/O port with internal pull-ups. Port 1 pins that

1–3

1 2 40 30 I/O T2 (P1.0): Timer/Counter 2 external count input/clockout (see Programmable

2 3 41 31 I T2EX (P1.1): Timer/Counter 2 Reload/Capture/Direction control

1–6 I/O Port 3: Port 3 is an 8-bit bidirectional I/O port with internal pull-ups. Port 3 pins that

13–195,7–13

10 11 5 1 I RxD (P3.0): Serial input port 11 13 7 2 O TxD (P3.1): Serial output port 12 14 8 I INT0 (P3.2): External interrupt 13 15 9 3 I INT1 (P3.3): External interrupt 14 16 10 4 I T0 (P3.4): Timer 0 external input 15 17 11 I T1 (P3.5): Timer 1 external input 16 18 12 5 O WR (P3.6): External data memory write strobe 17 19 13 6 O RD (P3.7): External data memory read strobe

operation.

written to them float and can be used as high-impedance inputs. Port 0 is also the multiplexed low-order address and data bus during accesses to external program and data memory. In this application, it uses strong internal pull-ups when emitting 1s. Port 0 also outputs the code bytes during program verification and received code bytes during EPROM programming. External pull-ups are required during program verification.

have 1s written to them are pulled high by the internal pull-ups and can be used as inputs. As inputs, port 1 pins that are externally pulled low will source current because of the internal pull-ups. (See DC Electrical Characteristics: IIL). Port 1 also receives the low-order address byte during program memory verification. Alternate functions for Port 1 include:

Clock-Out)

have 1s written to them are pulled high by the internal pull-ups and can be used as inputs. As inputs, port 2 pins that are externally being pulled low will source current because of the internal pull-ups. (See DC Electrical Characteristics: IIL). Port 2 emits the high-order address byte during fetches from external program memory and during accesses to external data memory that use 16-bit addresses (MOVX @DPTR). In this application, it uses strong internal pull-ups when emitting 1s. During accesses to ex ternal data memory th at use 8-bit addresses (MOV @Ri), port 2 emits the contents of the P2 special function register. Some Port 2 pins receive the high order address bits during EPROM programming and verification.

have 1s written to them are pulled high by the internal pull-ups and can be used as inputs. As inputs, port 3 pins that are externally being pulled low will source current because of the pull-ups. (See DC Electrical Characteristics: IIL). Port 3 also serves the special features of the 80C51 family, as listed below:

resets the device. An internal diffused resistor to VSS permits a power-on reset using only an external capacitor to VCC.

the address during an access to external memory. In normal operation, ALE is emitted at a constant rate of 1/6 (12-clock Mode) or 1/3 (6-clock Mode) the oscillator frequency , and can be used for external timing or clocking. Note that one ALE pulse is skipped during each access to external data memory. This pin is also the program pulse input (PROG) during EPROM programming. ALE can be disabled by setting SFR auxiliary.0. With this bit set, ALE will be active only during a MOVX instruction.

2003 Jan 24

Philips Semiconductors Product data

80C51 8-bit microcontroller family

4K/8K/16K/32K ROM/OTP, low voltage (2.7 to 5.5 V), low power, high speed (30/33 MHz)

PIN NUMBER

MNEMONIC NAME AND FUNCTIONTYPETSSOPLQFPPLCCDIP

PSEN 29 32 26 18 O Program Store Enable: The read strobe to external program memory. When the

EA/V

XTAL1 19 21 15 8 I Crystal 1: Input to the inverting oscillator amplifier and input to the internal clock

XTAL2 18 20 14 7 O Crystal 2: Output from the inverting oscillator amplifier.

NOTES:

To avoid “latch-up” effect at power-on, the voltage on any pin at any time must not be higher than V

1. Absent in the TSSOP38 package.

31 35 29 20 I External Access Enable/Programming Supply Voltage: EA must be externally held low to enable

device is executing code from the external program memory, PSEN is activated twice each machine cycle, except that two PSEN activations are skipped during each access to external data memory. PSEN is not activated during fetches from internal program memory.

the device to fetch code from external program memory locations 0000H to 0FFFH/1FFFH/3FFFH/7FFFH. If EA is held high, the device executes from internal program memory unless the program counter contains an address greater than the on-chip ROM/OTP. This pin also receives the 12.75 V programming supply voltage (VPP) during EPROM programming. If security bit 1 is programmed, EA will be internally latched on Reset.

generator circuits.

P80C3xX2; P80C5xX2;

P87C5xX2

+ 0.5 V or VSS – 0.5 V, respectively.

2003 Jan 24

Philips Semiconductors Product data

80C51 8-bit microcontroller family

4K/8K/16K/32K ROM/OTP, low voltage (2.7 to 5.5 V), low power, high speed (30/33 MHz)

P80C3xX2; P80C5xX2;

P87C5xX2

Table 1. Special Function Registers

SYMBOL DESCRIPTION

ACC* Accumulator E0H AUXR# Auxiliary 8EH – – – – – – – AO xxxxxxx0B AUXR1# Auxiliary 1 A2H – – – LPEP2WUPD 0 – DPS xxx000x0B B* B register F0H CKCON Clock Control Register 8FH – – – – – – – X2 xxx00000B DPTR: Data Pointer (2 bytes)

DPH Data Pointer High 83H 00H DPL Data Pointer Low 82H 00H

IE* Interrupt Enable A8H EA – ET2 ES ET1 EX1 ET0 EX0 0x000000B

IP* Interrupt Priority B8H – – PT2 PS PT1 PX1 PT0 PX0 xx000000B IPH# Interrupt Priority High B7H – – PT2H PSH PT1H PX1H PT0H PX0H xx000000B

P0* Port 0 80H AD7 AD6 AD5 AD4 AD3 AD2 AD1 AD0 FFH

P1* Port 1 90H – – – – – – T2EX T2 FFH

P2* Port 2 A0H AD15 AD14 AD13 AD12 AD11 AD10 AD9 AD8 FFH

P3* Port 3 B0H RD WR T1 T0 INT1 INT0 TxD RxD FFH

DIRECT

ADDRESS

BIT ADDRESS, SYMBOL, OR ALTERNATIVE PORT FUNCTION

MSB LSB

E7 E6 E5 E4 E3 E2 E1 E0

F7 F6 F5 F4 F3 F2 F1 F0

AF AE AD AC AB AA A9 A8

BF BE BD BC BB BA B9 B8

87 86 85 84 83 82 81 80

97 96 95 94 93 92 91 90

A7 A6 A5 A4 A3 A2 A1 A0

B7 B6 B5 B4 B3 B2 B1 B0

RESET VALUE

00H

PCON#1Power Control 87H SMOD1 SMOD0 – POF GF1 GF0 PD IDL 00xx0000B

D7 D6 D5 D4 D3 D2 D1 D0

PSW* Program Status Word D0H CY AC F0 RS1 RS0 OV – P 000000x0B

RACAP2H# Timer 2 Capture High CBH 00H RACAP2L# Timer 2 Capture Low CAH 00H

SADDR# Slave Address A9H 00H SADEN# Slave Address Mask B9H 00H

SBUF Serial Data Buffer 99H xxxxxxxxB

9F 9E 9D 9C 9B 9A 99 98

SCON* Serial Control 98H SP Stack Pointer 81H 07H

TCON* Timer Control 88H TF1 TR1 TF0 TR0 IE1 IT1 IE0 IT0 00H

T2CON* Timer 2 Control C8H TF2 EXF2 RCLK TCLK EXEN2 TR2 C/T2 CP/RL2 00H T2MOD# Timer 2 Mode Control C9H – – – – – – T2OE DCEN xxxxxx00B

TH0 Timer High 0 8CH 00H TH1 Timer High 1 8DH 00H TH2# T imer High 2 CDH 00H TL0 Timer Low 0 8AH 00H TL1 Timer Low 1 8BH 00H TL2# Timer Low 2 CCH 00H

TMOD Timer Mode 89H GATE C/T M1 M0 GATE C/T M1 M0 00H

NOTE:

Unused register bits that are not defined should not be set by the user’s program. If violated, the device could function incorrectly. * SFRs are bit addressable. # SFRs are modified from or added to the 80C51 SFRs. – Reserved bits.

1. Reset value depends on reset source.

2. LPEP – Low Power EPROM operation (OTP only)

SM0/FE

8F 8E 8D 8C 8B 8A 89 88

CF CE CD CC CB CA C9 C8

SM1 SM2 REN TB8 RB8 TI RI 00H

2003 Jan 24

Philips Semiconductors Product data

80C51 8-bit microcontroller family

4K/8K/16K/32K ROM/OTP, low voltage (2.7 to 5.5 V), low power, high speed (30/33 MHz)

OSCILLA T OR CHARACTERISTICS Using the oscillator

XTAL1 and XTAL2 are the input and output, respectively, of an inverting amplifier . The pins can be configured for use as an on-chip oscillator, as shown in the logic symbol.

To drive the device from an external clock source, XTAL1 should be driven while XTAL2 is left unconnected. However, minimum and maximum high and low times specified in the data sheet must be observed.

Clock Control Register (CKCON)

This device provides control of the 6-clock/12-clock mode by both an SFR bit (bit X2 in register CKCON and an OTP bit (bit OX2). When X2 is 0, 12-clock mode is activated. By setting this bit to 1, the system is switching to 6-clock mode. Having this option implemented as SFR bit, it can be accessed anytime and changed to either value. Changing X2 from 0 to 1 will result in executing user code at twice the speed, since all system time intervals will be divided by 2. Changing back from 6-clock to 12-clock mode will slow down running code by a factor of 2.

The OTP clock control bit (OX2) activates the 6-clock mode when programmed using a parallel programmer, superceding the X2 bit (CKCON.0). Please also see Table 2 below.

Table 2.

OX2 clock mode bit (can only be set by parallel programmer)

erased 0 12-clock mode

erased 1 6-clock mode programmed X 6-clock mode

Programmable Clock-Out

A 50% duty cycle clock can be programmed to be output on P1.0. This pin, besides being a regular I/O pin, has two alternate functions. It can be programmed:

1. to input the external clock for Timer/Counter 2, or

2. to output a 50% duty cycle clock ranging from 61 Hz to 4 MHz at a 16 MHz operating frequency in 12-clock mode (122 Hz to 8 MHz in 6-clock mode).

To configure the Timer/Counter 2 as a clock generator , bit C/T T2CON) must be cleared and bit T20E in T2MOD must be set. Bit TR2 (T2CON.2) also must be set to start the timer.

The Clock-Out frequency depends on the oscillator frequency and the reload value of Timer 2 capture registers (RCAP2H, RCAP2L) as shown in this equation:

Oscillator Frequency

n (65536–RCAP2H,RCAP2L)

Where:

n = 2 in 6-clock mode, 4 in 12-clock mode. (RCAP2H,RCAP2L) = the content of RCAP2H and RCAP2L

taken as a 16-bit unsigned integer.

In the Clock-Out mode Timer 2 roll-overs will not generate an interrupt. This is similar to when it is used as a baud-rate generator. It is possible to use Timer 2 as a baud-rate generator and a clock

X2 bit (CKCON.0)

CPU clock mode

(default)

2 (in

P80C3xX2; P80C5xX2;

P87C5xX2

generator simultaneously. Note, however, that the baud-rate and the Clock-Out frequency will be the same.

RESET

A reset is accomplished by holding the RST pin HIGH for at least two machine cycles (24 oscillator periods in 12-clock and 12 oscillator periods in 6-clock mode), while the oscillator is running. To insure a reliable power-up reset, the RST pin must be high long enough to allow the oscillator time to start up (normally a few milliseconds) plus two machine cycles. After the reset, the part runs in 12-clock mode, unless it has been set to 6-clock operation using a parallel programmer.

LOW POWER MODES Stop Clock Mode

The static design enables the clock speed to be reduced down to 0 MHz (stopped). When the oscillator is stopped, the RAM and Special Function Registers retain their values. This mode allows step-by-step utilization and permits reduced system power consumption by lowering the clock frequency down to any value. For lowest power consumption the Power Down mode is suggested.

Idle Mode

In idle mode (see Table 3), the CPU puts itself to sleep while all of the on-chip peripherals stay active. The instruction to invoke the idle mode is the last instruction executed in the normal operating mode before the idle mode is activated. The CPU contents, the on-chip RAM, and all of the special function registers remain intact during this mode. The idle mode can be terminated either by any enabled interrupt (at which time the process is picked up at the interrupt service routine and continued), or by a hardware reset which starts the processor in the same manner as a power-on reset.

Power-Down Mode

To save even more power, a Power Down mode (see Table 3) can be invoked by software. In this mode, the oscillator is stopped and the instruction that invoked Power Down is the last instruction executed. The on-chip RAM and Special Function Registers retain their values down to 2.0 V and care must be taken to return VCC to the minimum specified operating voltages before the Power Down Mode is terminated.

Either a hardware reset or external interrupt can be used to exit from Power Down. Reset redefines all the SFRs but does not change the on-chip RAM. An external interrupt allows both the SFRs and the on-chip RAM to retain their values. WUPD (AUXR1.3–Wakeup from Power Down) enables or disables the wakeup from power down with external interrupt. Where:

WUPD = 0: Disable WUPD = 1: Enable

To properly terminate Power Down, the reset or external interrupt should not be executed before V operating level and must be held active long enough for the oscillator to restart and stabilize (normally less than 10 ms).

To terminate Power Down with an external interrupt, INT0 must be enabled and configured as level-sensitive. Holding the pin low restarts the oscillator but bringing the pin back high completes the exit. Once the interrupt is serviced, the next instruction to be executed after RETI will be the one following the instruction that put the device into Power Down.

is restored to its normal

or INT1

2003 Jan 24

Philips Semiconductors Product data

80C51 8-bit microcontroller family

4K/8K/16K/32K ROM/OTP, low voltage (2.7 to 5.5 V), low power, high speed (30/33 MHz)

Low-Power EPROM operation (LPEP)

The EPROM array contains some analog circuits that are not required when V greater than 4 V . The LPEP bit (AUXR.4), when set, will powerdown these analog circuits resulting in a reduced supply current. This bit should be set ONLY for applications that operate at a V 4 V.

Design Consideration

When the idle mode is terminated by a hardware reset, the device normally resumes program execution from where it left off, up to two machine cycles before the internal reset algorithm takes control. On-chip hardware inhibits access to internal RAM in this event, but access to the port pins is not inhibited. To eliminate the possibility of an unexpected write when Idle is terminated by reset, the instruction

is less than 4 V, but are required for a V

less than

following the one that invokes Idle should not be one that writes to a port pin or to external memory.

ONCE Mode

The ONCE (“On-Circuit Emulation”) Mode facilitates testing and debugging of systems without the device having to be removed from the circuit. The ONCE Mode is invoked in the following way:

1. Pull ALE low while the device is in reset and PSEN

2. Hold ALE low as RST is deactivated. While the device is in ONCE Mode, the Port 0 pins go into a float

state, and the other port pins and ALE and PSEN high. The oscillator circuit remains active. While the device is in this mode, an emulator or test CPU can be used to drive the circuit. Normal operation is restored when a normal reset is applied.

P80C3xX2; P80C5xX2;

P87C5xX2

is high;

are weakly pulled

Table 3. External Pin Status During Idle and Power-Down Modes

MODE PROGRAM MEMORY ALE PSEN PORT 0 PORT 1 PORT 2 PORT 3

Idle Internal 1 1 Data Data Data Data Idle External 1 1 Float Data Address Data Power-down Internal 0 0 Data Data Data Data Power-down External 0 0 Float Data Data Data

TIMER 0 AND TIMER 1 OPERATION Timer 0 and Timer 1

The “Timer” or “Counter” function is selected by control bits C/T in the Special Function Register TMOD. These two Timer/Counters have four operating modes, which are selected by bit-pairs (M1, M0) in TMOD. Modes 0, 1, and 2 are the same for both Timers/Counters. Mode 3 is different. The four operating modes are described in the following text.

Mode 0

Putting either Timer into Mode 0 makes it look like an 8048 T imer, which is an 8-bit Counter with a divide-by-32 prescaler. Figure 2 shows the Mode 0 operation.

In this mode, the Timer register is configured as a 13-bit register . As the count rolls over from all 1s to all 0s, it sets the Timer interrupt flag TFn. The counted input is enabled to the Timer when TRn = 1 and either GA TE = 0 or INTn Timer to be controlled by external input INTn measurements). TRn is a control bit in the Special Function Register TCON (Figure 3).

The 13-bit register consists of all 8 bits of THn and the lower 5 bits of TLn. The upper 3 bits of TLn are indeterminate and should be ignored. Setting the run flag (TRn) does not clear the registers.

Mode 0 operation is the same for Timer 0 as for Timer 1. There are two different GA TE bits, one for Timer 1 (TMOD.7) and one for Timer 0 (TMOD.3).

= 1. (Setting GATE = 1 allows the

, to facilitate pulse width

Mode 1

Mode 1 is the same as Mode 0, except that the Timer register is being run with all 16 bits.

Mode 2

Mode 2 configures the Timer register as an 8-bit Counter (TLn) with automatic reload, as shown in Figure 4. Overflow from TLn not only sets TFn, but also reloads TLn with the contents of THn, which is preset by software. The reload leaves THn unchanged.

Mode 2 operation is the same for Timer 0 as for Timer 1.

Mode 3

Timer 1 in Mode 3 simply holds its count. The effect is the same as setting TR1 = 0.

Timer 0 in Mode 3 establishes TL0 and TH0 as two separate counters. The logic for Mode 3 on Timer 0 is shown in Figure 5. TL0 uses the Timer 0 control bits: C/T pin INT0 cycles) and takes over the use of TR1 and TF1 from Timer 1. Thus, TH0 now controls the “Timer 1” interrupt.

Mode 3 is provided for applications requiring an extra 8-bit timer on the counter. With Timer 0 in Mode 3, an 80C51 can look like it has three Timer/Counters. When Timer 0 is in Mode 3, Timer 1 can be turned on and off by switching it out of and into its own Mode 3, or can still be used by the serial port as a baud rate generator, or in fact, in any application not requiring an interrupt.

. TH0 is locked into a timer function (counting machine

, GATE, TR0, and TF0 as well as

2003 Jan 24

Philips Semiconductors Product data

80C51 8-bit microcontroller family

P80C3xX2; P80C5xX2;

4K/8K/16K/32K ROM/OTP, low voltage (2.7 to 5.5 V), low power, high speed (30/33 MHz)

TMOD Address = 89H Reset Value = 00H

Not Bit Addressable

76543 2 1 0

GATE C/T M1

TIMER 1 TIMER 0

BIT SYMBOL FUNCTION

TMOD.3/ GA TE Gating control when set. Timer/Counter “n” is enabled only while “INTn TMOD.7 “TRn” control pin is set. when cleared Timer “n” is enabled whenever “TRn” control bit is set.

TMOD.2/ C/T

Timer or Counter Selector cleared for Timer operation (input from internal system clock.)

TMOD.6 Set for Counter operation (input from “Tn” input pin).

M1 M0 OPERATING

0 0 8048 Timer: “TLn” serves as 5-bit prescaler. 0 1 16-bit Timer/Counter: “THn” and “TLn” are cascaded; there is no prescaler. 1 0 8-bit auto-reload Timer/Counter: “THn” holds a value which is to be reloaded

into “TLn” each time it overflows.

1 1 (Timer 0) TL0 is an 8-bit Timer/Counter controlled by the standard Timer 0 control bits.

TH0 is an 8-bit timer only controlled by Timer 1 control bits.

1 1 (Timer 1) Timer/Counter 1 stopped.

M0 GATE C/T

M1 M0

” pin is high and

SU01580

P87C5xX2

Figure 1. Timer/Counter 0/1 Mode Control (TMOD) Register

OSC

Timer n Gate bit

INTn Pin

*d = 6 in 6-clock mode; d = 12 in 12-clock mode.

÷ d*

Tn Pin

TRn

C/T = 0

C/T = 1

Control

TLn

(5 Bits)

THn

(8 Bits)

Figure 2. Timer/Counter 0/1 Mode 0: 13-Bit Timer/Counter

TFn Interrupt

SU01618

2003 Jan 24

Philips Semiconductors Product data

80C51 8-bit microcontroller family

P80C3xX2; P80C5xX2;

4K/8K/16K/32K ROM/OTP, low voltage (2.7 to 5.5 V), low power, high speed (30/33 MHz)

TCON Address = 88H Reset Value = 00H

Bit Addressable

76543210

IE0IT1IE1TR0TF0TR1TF1

BIT SYMBOL FUNCTION

TCON.7 TF1 Timer 1 overflow flag. Set by hardware on Timer/Counter overflow .

Cleared by hardware when processor vectors to interrupt routine, or clearing the bit in software. TCON.6 TR1 Timer 1 Run control bit. Set/cleared by software to turn Timer/Counter on/off. TCON.5 TF0 Timer 0 overflow flag. Set by hardware on Timer/Counter overflow .

Cleared by hardware when processor vectors to interrupt routine, or by clearing the bit in software. TCON.4 TR0 Timer 0 Run control bit. Set/cleared by software to turn Timer/Counter on/off. TCON.3 IE1 Interrupt 1 Edge flag. Set by hardware when external interrupt edge detected.

Cleared when interrupt processed. TCON.2 IT1 Interrupt 1 type control bit. Set/cleared by software to specify falling edge/low level triggered

external interrupts. TCON.1 IE0 Interrupt 0 Edge flag. Set by hardware when external interrupt edge detected.

Cleared when interrupt processed. TCON.0 IT0 Interrupt 0 Type control bit. Set/cleared by software to specify falling edge/low level

triggered external interrupts.

IT0

P87C5xX2

SU01516

OSC

Timer n Gate bit

INTn Pin

*d = 6 in 6-clock mode; d = 12 in 12-clock mode.

÷ d*

Tn Pin

TRn

Figure 3. Timer/Counter 0/1 Control (TCON) Register

C/T = 0

= 1

C/T

Control

TLn

(8 Bits)

THn

(8 Bits)

Reload

Figure 4. Timer/Counter 0/1 Mode 2: 8-Bit Auto-Reload

TFn

Interrupt

SU01619

2003 Jan 24

Philips Semiconductors Product data

80C51 8-bit microcontroller family

4K/8K/16K/32K ROM/OTP, low voltage (2.7 to 5.5 V), low power, high speed (30/33 MHz)

OSC

Timer 0 Gate bit

INT0 Pin

OSC

*d = 6 in 6-clock mode; d = 12 in 12-clock mode.

T0 Pin

÷ d*

TR0

÷ d*

TR1

C/T = 0

= 1

C/T

Control

TL0

(8 Bits)

TH0

(8 Bits)

P80C3xX2; P80C5xX2;

P87C5xX2

TF0

TF1

Interrupt

SU01620

Figure 5. Timer/Counter 0 Mode 3: Two 8-Bit Counters

TIMER 2 OPERATION Timer 2

Timer 2 is a 16-bit Timer/Counter which can operate as either an event timer or an event counter, as selected by C/T

2 in the special function register T2CON (see Figure 6). Timer 2 has three operating modes: Capture, Auto-reload (up or down counting), and Baud Rate Generator, which are selected by bits in the T2CON as shown in Table 4.

Capture Mode

In the capture mode there are two options which are selected by bit EXEN2 in T2CON. If EXEN2=0, then timer 2 is a 16-bit timer or counter (as selected by C/T

2 in T2CON) which, upon overflowing, sets bit TF2, the timer 2 overflow bit. This bit can be used to generate an interrupt (by enabling the Timer 2 interrupt bit in the IE register). If EXEN2=1, Timer 2 operates as described above, but with the added feature that a 1-to-0 transition at external input T2EX causes the current value in the Timer 2 registers, TL2 and TH2, to be captured into registers RCAP2L and RCAP2H, respectively. In addition, the transition at T2EX causes bit EXF2 in T2CON to be set, and EXF2 (like TF2) can generate an interrupt (which vectors to the same location as Timer 2 overflow interrupt. The Timer 2 interrupt service routine can interrogate TF2 and EXF2 to determine which event caused the interrupt). The capture mode is illustrated in Figure 7 (There is no reload value for TL2 and TH2 in this mode. Even when a capture event occurs from T2EX, the counter keeps on counting T2EX pin transitions or osc/12 (12-clock Mode) or osc/6 (6-clock Mode) pulses).

Auto-Reload Mode (Up or Down Counter)

In the 16-bit auto-reload mode, Timer 2 can be configured as either a timer or counter (C/T or down. The counting direction is determined by bit DCEN (Down

2 in T2CON), then programmed to count up

Counter Enable) which is located in the T2MOD register (see Figure 8). After reset, DCEN=0 which means Timer 2 will default to counting up. If DCEN is set, Timer 2 can count up or down depending on the value of the T2EX pin.

Figure 9 shows Timer 2 which will count up automatically since DCEN=0. In this mode there are two options selected by bit EXEN2 in T2CON register. If EXEN2=0, then T imer 2 counts up to 0FFFFH and sets the TF2 (Overflow Flag) bit upon overflow. This causes the Timer 2 registers to be reloaded with the 16-bit value in RCAP2L and RCAP2H. The values in RCAP2L and RCAP2H are preset by software.

If EXEN2=1, then a 16-bit reload can be triggered either by an overflow or by a 1-to-0 transition at input T2EX. This transition also sets the EXF2 bit. The Timer 2 interrupt, if enabled, can be generated when either TF2 or EXF2 are 1.

In Figure 10 DCEN=1 which enables Timer 2 to count up or down. This mode allows pin T2EX to control the direction of count. When a logic 1 is applied at pin T2EX, Timer 2 will count up. Timer 2 will overflow at 0FFFFH and set the TF2 flag, which can then generate an interrupt, if the interrupt is enabled. This timer overflow also causes the 16-bit value in RCAP2L and RCAP2H to be reloaded into the timer registers TL2 and TH2.

A logic 0 applied to pin T2EX causes Timer 2 to count down. The timer will underflow when TL2 and TH2 become equal to the value stored in RCAP2L and RCAP2H. A Timer 2 underflow sets the TF2 flag and causes 0FFFFH to be reloaded into the timer registers TL2 and TH2.

The external flag EXF2 toggles when Timer 2 underflows or overflows. This EXF2 bit can be used as a 17th bit of resolution if needed. The EXF2 flag does not generate an interrupt in this mode of operation.

2003 Jan 24

Philips Semiconductors Product data

80C51 8-bit microcontroller family

P80C3xX2; P80C5xX2;

4K/8K/16K/32K ROM/OTP, low voltage (2.7 to 5.5 V), low power, high speed (30/33 MHz)

Table 4. Timer 2 Operating Modes

RCLK + TCLK CP/RL2 TR2 MODE

0 0 1 16-bit Auto-reload 0 1 1 16-bit Capture 1 X 1 Baud rate generator

X X 0 (off)

T2CON Address = C8H Reset Value = 00H

Bit Addressable

765432 10

TF2 EXF2 RCLK TCLK EXEN2 TR2 C/T

Symbol Position Name and Significance

TF2 T2CON.7 Timer 2 overflow flag set by a Timer 2 overflow and must be cleared by software. TF2 will not be set

EXF2 T2CON.6 Timer 2 external flag set when either a capture or reload is caused by a negative transition on T2EX and

RCLK T2CON.5 Receive clock flag. When set, causes the serial port to use Timer 2 overflow pulses for its receive clock

TCLK T2CON.4 Transmit clock flag. When set, causes the serial port to use Timer 2 overflow pulses for its transmit clock

EXEN2 T2CON.3 Timer 2 external enable flag. When set, allows a capture or reload to occur as a result of a negative

TR2 T2CON.2 Start/stop control for Timer 2. A logic 1 starts the timer. C/T

2 T2CON.1 Timer or counter select. (Timer 2)

CP/RL

2 T2CON.0 Capture/Reload flag. When set, captures will occur on negative transitions at T2EX if EXEN2 = 1. When

when either RCLK or TCLK = 1.

EXEN2 = 1. When Timer 2 interrupt is enabled, EXF2 = 1 will cause the CPU to vector to the Timer 2 interrupt routine. EXF2 must be cleared by software. EXF2 does not cause an interrupt in up/down counter mode (DCEN = 1).

in modes 1 and 3. RCLK = 0 causes Timer 1 overflow to be used for the receive clock.

in modes 1 and 3. TCLK = 0 causes Timer 1 overflows to be used for the transmit clock.

transition on T2EX if Timer 2 is not being used to clock the serial port. EXEN2 = 0 causes Timer 2 to ignore events at T2EX.

0 = Internal timer (OSC/12 in 12-clock mode or OSC/6 in 6-clock mode) 1 = External event counter (falling edge triggered).

cleared, auto-reloads will occur either with Timer 2 overflows or negative transitions at T2EX when EXEN2 = 1. When either RCLK = 1 or TCLK = 1, this bit is ignored and the timer is forced to auto-reload on Timer 2 overflow .

2 CP/RL2

P87C5xX2

SU01621

2003 Jan 24

Figure 6. Timer/Counter 2 (T2CON) Control Register

Philips Semiconductors Product data

80C51 8-bit microcontroller family

4K/8K/16K/32K ROM/OTP, low voltage (2.7 to 5.5 V), low power, high speed (30/33 MHz)

OSC

T2EX Pin

*n = 6 in 6-clock mode; n = 12 in 12-clock mode.

T2 Pin

÷ n*

Transition

Detector

C/T2 = 0

C/T

EXEN2

2 = 1

Control

TR2

Control

Capture

TL2

(8 bits)

RCAP2L RCAP2H

TH2

(8 bits)

P80C3xX2; P80C5xX2;

P87C5xX2

TF2

Timer 2

Interrupt

EXF2

SU01622

Figure 7. Timer 2 in Capture Mode

T2MOD Address = 0C9H Reset Value = XXXX XX00B

Not Bit Addressable

76543210

— — — — — — T2OE DCEN

Symbol Position Function

— Not implemented, reserved for future use.* T2OE T2MOD.1 Timer 2 Output Enable bit. DCEN T2MOD.0 Down Count Enable bit. When set, this allows Timer 2 to be configured as an up/down

counter.

* User software should not write 1s to reserved bits. These bits may be used in future 8051 family products to invoke new features.

In that case, the reset or inactive value of the new bit will be 0, and its active value will be 1. The value read from a reserved bit is indeterminate.

SU01519

Figure 8. Timer 2 Mode (T2MOD) Control Register

2003 Jan 24

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