P89C51RB2BA datasheet(6/52 Pages) PHILIPS

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Philips Semiconductors

Preliminary specification

89C51RB2/89C51RC2/

89C51RD2

80C51 8-bit Flash microcontroller family

16KB/32KB/64KB ISP/IAP Flash with 512B/512B/1KB RAM

1999 Sep 23

PIN DESCRIPTIONS

MNEMONIC

PIN NUMBER

TYPE

NAME AND FUNCTION

MNEMONIC

PDIP

PLCC

PQFP

TYPE

NAME AND FUNCTION

VSS

Ground: 0 V reference.

VCC

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.

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 on all pins

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 source current because of the internal

pull-ups. (See DC Electrical Characteristics: IIL).

Alternate functions for 89C51RB2/RC2/RD2 Port 1 include:

I/O

T2 (P1.0): Timer/Counter 2 external count input/Clockout (see Programmable

Clock-Out)

T2EX (P1.1): Timer/Counter 2 Reload/Capture/Direction Control

ECI (P1.2): External Clock Input to the PCA

I/O

CEX0 (P1.3): Capture/Compare External I/O for PCA module 0

I/O

CEX1 (P1.4): Capture/Compare External I/O for PCA module 1

I/O

CEX2 (P1.5): Capture/Compare External I/O for PCA module 2

I/O

CEX3 (P1.6): Capture/Compare External I/O for PCA module 3

I/O

CEX4 (P1.7): Capture/Compare External I/O for PCA module 4

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 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 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. (See DC Electrical Characteristics: IIL). Port 3 also serves

the special features of the 89C51RB2/RC2/RD2, as listed below:

RxD (P3.0): Serial input port

TxD (P3.1): Serial output port

INT0 (P3.2): External interrupt

INT1 (P3.3): External interrupt

T0 (P3.4): Timer 0 external input

T1 (P3.5): Timer 1 external input

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

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

RST

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

resets the device. An internal diffused resistor to VSS permits a power-on reset

using only an external capacitor to VCC.

ALE

Address Latch Enable: Output pulse for latching the low byte of the address

during an access to external memory. In normal operation, ALE is emitted twice

every machine cycle, and can be used for external timing or clocking. Note that one

ALE pulse is skipped during each access to external data memory. ALE can be

disabled by setting SFR auxiliary.0. With this bit set, ALE will be active only during a

MOVX instruction.

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