MC68HC908GR4MP datasheet(121/286 Pages) FREESCALE

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MC68HC908GR8 • MC68HC908GR4 Data Sheet, Rev. 7

Freescale Semiconductor

121

Chapter 13

Keyboard Interrupt (KBI)

13.1 Introduction

The keyboard interrupt module (KBI) provides four independently maskable external interrupts which are

accessible via PTA0–PTA3. When a port pin is enabled for keyboard interrupt function, an internal pullup

device is also enabled on the pin.

13.2 Features

•

Four keyboard interrupt pins with separate keyboard interrupt enable bits and one keyboard

interrupt mask

•

Hysteresis buffers

•

Programmable edge-only or edge- and level- interrupt sensitivity

•

Exit from low-power modes

•

I/O (input/output) port bit(s) software configurable with pullup device(s) if configured as input port

bit(s)

13.3 Functional Description

Writing to the KBIE3–KBIE0 bits in the keyboard interrupt enable register independently enables or

disables each port A pin as a keyboard interrupt pin. Enabling a keyboard interrupt pin also enables its

internal pullup device. A low level applied to an enabled keyboard interrupt pin latches a keyboard

interrupt request.

Figure 13-1. Keyboard Module Block Diagram

KB0IE

KB3IE

KEYBOARD

INTERRUPT

CLR

VDD

MODEK

IMASKK

KEYBOARD

INTERRUPT FF

REQUEST

VECTOR FETCH

DECODER

ACKK

INTERNAL BUS

RESET

TO PULLUP

KBD3

KBD0

TO PULLUP

SYNCHRONIZER

KEYF

ENABLE

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