Philips Semiconductors
P89LPC920/921/922/9221
8-bit microcontrollers with two-clock 80C51 core
Product data Rev. 08 — 15 December 2004 7 of 46
9397 750 14469
© Koninklijke Philips Electronics N.V. 2004. All rights reserved.
P1.0 to P1.7 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:
12 I/O P1.0 — Port 1 bit 0.
O TXD — Transmitter output for the serial port.
11 I/O P1.1 — Port 1 bit 1.
I RXD — Receiver input for the serial port.
10 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 — I
2
C serial clock input/output.
9 I/O P1.3 — Port 1 bit 3 (open-drain when used as output).
I
INT0 — External interrupt 0 input.
I/O SDA — I
2
C serial data input/output.
8 I/O P1.4 — Port 1 bit 4. High current source (P89LPC9221).
I
INT1 — External interrupt 1 input.
4IP1.5 — Port 1 bit 5 (input only).
I
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 V
DD
has
reached its specified level. When system power is removed V
DD
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 V
DD
falls below the minimum specified
operating voltage.
3 I/O P1.6 — Port 1 bit 6. High current source (P89LPC9221).
2 I/O P1.7 — Port 1 bit 7. High current source (P89LPC9221).
Table 3: Pin description
…continued
Symbol Pin Type Description
