Philips Semiconductors

Product specification

80C550/83C550/87C550

80C51 8-bit microcontroller family

4K/128 OTP/ROM/ROMless, 8 channel 8 bit A/D, watchdog timer

1998 May 01

5

PIN DESCRIPTION

PIN NO.

MNEMONIC

DIP

LCC

TYPE

NAME AND FUNCTION

20

24

I

Ground: 0V reference.

40

44

I

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

1

1

I

Analog Power Supply: Analog supply voltage.

2

4

I

Analog Ground: Analog 0V reference.

Vref+

Vref–

2

3

I

I

P0.0–0.7

39–32

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-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 S87C550. External pull-ups are required during program verification.

P1.0–P1.7

3–8

5–12

I

Port 1: Port 1 is an 8-bit input only port (6-bit in the DIP package; bits P1.6 and P1.7 are not

implemented). Port 1 digital input can be read out any time.

ADC0–ADC7

3–8

5–12

ADCx: Inputs to the analog multiplexer input of the 8-bit A/D. There are only six A/D inputs in the

DIP package.

P2.0–P2.7

21–28

25–32

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 pull-ups. (See DC

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

14–21

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. (See DC Electrical

10

14

I

RxD (P3.0): Serial input port

11

15

O

TxD (P3.1): Serial output port

12

16

I

INT0 (P3.2): External interrupt

13

17

I

INT1 (P3.3): External interrupt

14

18

I

T0 (P3.4): Timer 0 external input

15

19

I

T1 (P3.5): Timer 1 external input

16

20

O

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

17

21

O

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

RST

9

13

I

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

ALE/PROG

30

34

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

33

O

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

31

35

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 to 0FFFH. If EA is held

high, the device executes from internal program memory unless the program counter contains an

address greater than 0FFFH. For the 80C550 ROMless part, EA must be held low for the part to

EPROM programming.

XTAL1

19

23

I

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

XTAL2

18

22

O

Crystal 2: Output from the inverting oscillator amplifier.