T89C5115-RATIM datasheet(5/105 Pages) ATMEL

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T89C5115

4128A–8051–04/02

P3.0:7

I/O

Port 3:

Is an 8-bit bi-directional I/O port with internal pull-ups. Port 3 pins that have 1’s

written to them are pulled high by the internal pull-up transistors and can be used as

inputs in this state. As inputs, Port 3 pins that are being pulled low externally will be a

source of current (IIL, see section "Electrical Characteristic") because of the internal

pull-ups.

The output latch corresponding to a secondary function must be programmed to one

for that function to operate (except for TxD ). The secondary functions are assigned

to the pins of port 3 as follows:

P3.0/RxD:

Receiver data input (asynchronous) or data input/output (synchronous) of the serial

interface

P3.1/TxD:

Transmitter data output (asynchronous) or clock output (synchronous) of the serial

interface

P3.2/INT0:

External interrupt 0 input/timer 0 gate control input

P3.3/INT1:

External interrupt 1 input/timer 1 gate control input

P3.4/T0:

Timer 0 counter input

P3.5/T1:

Timer 1 counter input

It can drive CMOS inputs without external pull-ups.

P4.0:1

I/O

Port 4:

Is an 2-bit bi-directional I/O port with internal pull-ups. Port 4 pins that have 1’s

written to them are pulled high by the internal pull-ups and can be used as inputs in

this state. As inputs, Port 4 pins that are being pulled low externally will be a source

of current (IIL, on the datasheet) because of the internal pull-up transistor.

It can drive CMOS inputs without external pull-ups.

RESET

I/O

Reset:

A high level on this pin during two machine cycles while the oscillator is running

resets the device. An internal pull-down resistor to VSS permits power-on reset

using only an external capacitor to VCC.

XTAL1

XTAL1:

Input of the inverting oscillator amplifier and input of the internal clock generator

circuits. To drive the device from an external clock source, XTAL1 should be driven,

while XTAL2 is left unconnected. To operate above a frequency of 16 MHz, a duty

cycle of 50% should be maintained.

XTAL2

XTAL2:

Output from the inverting oscillator amplifier.

Table 1. Pin Description (Continued)

Pin Name

Type

Description

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