89LPC925 datasheet(7/49 Pages) PHILIPS

7 / 49 page

Philips Semiconductors

P89LPC924/925

8-bit microcontrollers with accelerated two-clock 80C51 core

Product data

Rev. 03 — 15 December 2004

7 of 49

9397 750 14471

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 8.13.1 “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. When using an oscillator

frequency above 12 MHz, the reset input function of P1.5 must be enabled. An

external circuit is required to hold the device in reset at power-up until VDD has

reached its speciﬁed level. When system power is removed VDD will fall below the

minimum speciﬁed operating voltage. When using an oscillator frequency above

12 MHz, in some applications, an external brownout detect circuit may be

required to hold the device in reset when VDD falls below the minimum speciﬁed

operating voltage.

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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