P89LPC921 datasheet(18/45 Pages) PHILIPS

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Philips Semiconductors

P89LPC920/921/922

8-bit microcontrollers with two-clock 80C51 core

Product data

Rev. 06 — 21 November 2003

18 of 45

9397 750 12285

8.12 I/O ports

The P89LPC920/921/922 has three I/O ports: Port 0, Port 1, and Port 3. Ports 0 and

1 are 8-bit ports, and Port 3 is a 2-bit port. The exact number of I/O pins available

depend upon the clock and reset options chosen, as shown in Table 6.

8.12.1

Port conﬁgurations

All but three I/O port pins on the P89LPC920/921/922 may be conﬁgured by software

to one of four types on a bit-by-bit basis. These are: quasi-bidirectional (standard

80C51 port outputs), push-pull, open drain, and input-only. Two conﬁguration

registers for each port select the output type for each port pin.

P1.5 (RST) can only be an input and cannot be conﬁgured.

P1.2 (SCL/T0) and P1.3 (SDA/INT0) may only be conﬁgured to be either input-only or

open-drain.

Fig 6.

Interrupt sources, interrupt enables, and power-down wake-up sources.

002aaa418

IE0

EX0

IE1

EX1

BOPD

EBO

KBIF

EKBI

INTERRUPT

TO CPU

WAKE-UP

(IF IN POWER-DOWN)

EWDRT

CMF2

CMF1

EA (IE0.7)

TF0

ET0

TF1

ET1

TI & RI/RI

ES/ESR

EST

EI2C

RTCF

ERTC

(RTCCON.1)

WDOVF

Table 6:

Number of I/O pins available

Clock source

Reset option

Number of I/O pins

(20-pin package)

On-chip oscillator or watchdog oscillator

No external reset (except during power-up)

External RST pin supported

External clock input

No external reset (except during power-up)

External RST pin supported

Low/medium/high speed oscillator

(external crystal or resonator)

No external reset (except during power-up)

External RST pin supported

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