2001 Apr 06

7

Philips Semiconductors

Preliminary specification

P87C51MB2/P87C51MC2

80C51 8-bit microcontroller family with extended memory

64KB/96KB OTP with 2KB/3KB RAM

PIN DESCRIPTIONS

MNEMONIC

PIN NO.

TYPE NAME AND FUNCTION

P0.0 - P0.7

43 - 36

I/O

Port 0: Port 0 is an open drain, bidirectional I/O port. Port 0 pins that have 1s written to

them float and can be used as high-impendance 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.

P1.0 - P1.7

2 - 9

I/O

Port 1: Port 1 is an 8-bit bidirectional I/O port with internal pull-ups on all pins. Port 1 pins

that 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. (Note: When SFR bit SPEN (SPCTL.6) is ’1’, the pull-ups at P1.4 and

P1.5 are disabled.)

2

I/O

P1.0

T2

Timer/Counter 2 external count input/Clockout

3

I

P1.1

T2EX

Timer/Counter 2 Reload/Capture/Direction Control

4

I

P1.2

ECI

External Clock Input to the PCA

5

I/O

P1.3

CEX0

Capture/Compare External I/O for PCA module 0

6

I/O

P1.4

CEX1

Capture/Compare External I/O for PCA module 1 (with pull-up on

pin)

I/O

MOSI

SPI Master Out/Slave In (Selected when SFR bit SPEN (SPCTL.6)

is ’1’, in which case the pull-up for this pin is disabled)

7

I/O

P1.5

CEX2

Capture/Compare External I/O for PCA module 2 (with pull-up on

pin)

I/O

SPICLK

SPI Clock (Selected when SFR bit SPEN (SPCTL.6) is ’1’, in which

case the pull-up for this pin is disabled)

8

I/O

P1.6

CEX3

Capture/Compare External I/O for PCA module 3

9

I/O

P1.7

CEX4

Capture/Compare External I/O for PCA module 4

P2.0 - P2.7

24 - 31

I/O

Port 2: Port 2 is a 8-bit bidirectional I/O port with internal pull-ups. Port 2 pins that 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

address byte during fetches from external program memory and during accesses to

external data memory that use 16-bit addresses ( MOVX @ DPTR) or 23-bit addresses

(MOVX @EPTR, EMOV). In this application, it uses strong internal pull-ups when emitting

1s. During accesses to external data memory that use 8-bit addresses ( MOV @ Ri), port2

emits the contents of the P2 Special Function Register.

Note that when 23-bit address is used, address bits A16-A22 will be output to P2.0-P2.6

when ALE is High, and address bits A8-A14 are output to P2.0-P2.6 when ALE is Low.

Address bit A15 is output on P2.7 regardless of ALE.

P3.0 - P3.7

11,13 -19

I/O

Port 3: Port 3 is an 8-bit bidirectional I/O port with internal pull-ups. Port 3 pins that 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 pulled low will source current because of the internal

pull-ups.

11

I

P3.0

RXD0

Serial input port 0

13

O

P3.1

TXD0

Serial output port 0

14

I

P3.2

INT0

External interrupt 0

15

I

P3.3

INT1

External interrupt 1

16

I

P3.4

T0

Timer0 external input

17

I

P3.5

T1

Timer1 external input

18

O

P3.6

WR

External data memory write strobe

19

O

P3.7

RD

External data memory read strobe