AT89C5131A-RDTUM datasheet(88/188 Pages) ATMEL

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4337K–USB–04/08

AT89C5130A/31A-M

17. Keyboard Interface

17.1

Introduction

The AT89C5130A/31A-M implements a keyboard interface allowing the connection of a 8 x n

matrix keyboard. It is based on 8 inputs with programmable interrupt capability on both high or

low level. These inputs are available as an alternate function of P1 and allow to exit from idle

and power down modes.

17.2

Description

The keyboard interface communicates with the C51 core through 3 special function registers:

KBLS, the Keyboard Level Selection register (Table 17-3), KBE, The Keyboard interrupt Enable

17.2.1

Interrupt

The keyboard inputs are considered as 8 independent interrupt sources sharing the same inter-

rupt vector. An interrupt enable bit (KBD in IE1) allows global enable or disable of the keyboard

interrupt (see Figure 17-1). As detailed in Figure 17-2 each keyboard input has the capability to

detect a programmable level according to KBLS.x bit value. Level detection is then reported in

interrupt flags KBF.x that can be masked by software using KBE.x bits.

This structure allow keyboard arrangement from 1 by n to 8 by n matrix and allow usage of P1

inputs for other purpose.

Figure 17-1. Keyboard Interface Block Diagram

Figure 17-2. Keyboard Input Circuitry

P1.0

Keyboard Interface

Interrupt Request

KBD

IE1.0

Input Circuitry

P1.1

Input Circuitry

P1.2

Input Circuitry

P1.3

Input Circuitry

P1.4

Input Circuitry

P1.5

Input Circuitry

P1.6

Input Circuitry

P1.7

Input Circuitry

KBDIT

P1:x

KBE.x

KBF.x

KBLS.x

Vcc

Internal Pull-up

AT89C5131A-RDTUM Datasheet(PDF) 88 Page - ATMEL Corporation

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