P89LPC921 datasheet(7/45 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

7 of 45

9397 750 12285

P1.0 - P1.7

12, 11, 10,

9, 8, 4, 3,

I/O, I [1] Port 1: Port 1 is an 8-bit I/O port with a user-conﬁgurable output type, except for three

pins as noted below. During reset Port 1 latches are conﬁgured in the input only mode

with the internal pull-up disabled. The operation of the conﬁgurable Port 1 pins as inputs

and outputs depends upon the port conﬁguration selected. Each of the conﬁgurable

port pins are programmed independently. Refer to Section 8.12.1 “Port conﬁgurations”

and Table 8 “DC electrical characteristics” for details. P1.2 - P1.3 are open drain when

used as outputs. P1.5 is input only.

All pins have Schmitt triggered inputs.

Port 1 also provides various special functions as described below:

I/O

P1.0 — Port 1 bit 0.

TXD — Transmitter output for the serial port.

I/O

P1.1 — Port 1 bit 1.

RXD — Receiver input for the serial port.

I/O

P1.2 — Port 1 bit 2 (open-drain when used as output).

I/O

T0 — Timer/counter 0 external count input or overﬂow output (open-drain when used as

output).

I/O

SCL — I2C serial clock input/output.

I/O

P1.3 — Port 1 bit 3 (open-drain when used as output).

INT0 — External interrupt 0 input.

I/O

SDA — I2C serial data input/output.

I/O

P1.4 — Port 1 bit 4.

INT1 — External interrupt 1 input.

P1.5 — Port 1 bit 5 (input only).

RST — External Reset input (if selected via FLASH conﬁguration). A LOW on this pin

resets the microcontroller, causing I/O ports and peripherals to take on their default

states, and the processor begins execution at address 0.

I/O

P1.6 — Port 1 bit 6.

I/O

P1.7 — Port 1 bit 7.

Table 3:

Pin description…continued

Symbol

Type

Description

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