Philips Semiconductors

Product specification

87C652/87C654

80C51 8-bit microcontroller

1999 Jul 23

5

PIN DESCRIPTIONS

PIN NUMBER

MNEMONIC

DIP

LCC

QFP

TYPE

NAME AND FUNCTION

20

22

16

I

Ground: 0 V reference.

40

44

38

I

Power Supply: This is the power supply voltage for normal, idle, and power-down operation.

P0.0–0.7

39–32

43–36

37–30

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-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 in the 87C654. External pull-ups are required during

program verification.

P1.0–P1.7

1–8

2–9

40–44,

1–3

I/O

Port 1: Port 1 is an 8-bit bidirectional I/O port with internal pull-ups, except P1.6 and P1.7

which are open drain. 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

Port 1 also receives the low-order address byte during program memory verification.

Alternate functions include:

P1.6

7

8

2

I/O

P1.7

8

9

3

I/O

P2.0–P2.7

21–28

24–31

18–25

I/O

Port 2: Port 2 is an 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 internal

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 external data memory that use 8-bit

addresses (MOV @Ri), port 2 emits the contents of the P2 special function register.

P3.0–P3.7

10–17

11,

13–19

5,

7–13

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 being pulled low will source current because of the pull-ups.

family, as listed below:

10

11

5

I

RxD (P3.0): Serial input port

11

13

7

O

TxD (P3.1): Serial output port

12

14

8

I

INT0 (P3.2): External interrupt

13

15

9

I

INT1 (P3.3): External interrupt

14

16

10

I

T0 (P3.4): Timer 0 external input

15

17

11

I

T1 (P3.5): Timer 1 external input

16

18

12

O

WR (P3.6): External data memory write strobe

17

19

13

O

RD (P3.7): External data memory read strobe

RST

9

10

4

I

Reset: A high on this pin for two machine cycles while the oscillator is running, resets the

ALE/PROG

30

33

27

I/O

Address Latch Enable/Program Pulse: Output pulse for latching the low byte of the

address during an access to external memory. In normal operation, ALE is emitted at a

constant rate of 1/6 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.

PSEN

29

32

26

O

Program Store Enable: The read strobe to external program memory. When the 87C654 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.

31

35

29

I

External Access Enable/Programming Supply Voltage: EA must be externally held low to

enable the device to fetch code from external program memory locations 0000H and 1FFFH

for 87C652 and 3FFFH for 87C654. If EA is held high, the device executes from internal

program memory unless the program counter contains an address greater than 3FFFH. This

XTAL1

19

21

15

I

Crystal 1: Input to the inverting oscillator amplifier and input to the internal clock generator

circuits.

XTAL2

18

20

14

O

Crystal 2: Output from the inverting oscillator amplifier.

NOTE: