M38C89MB datasheet(20/55 Pages) RENESAS

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SINGLE-CHIP 8-BIT CMOS MICROCOMPUTER

MITSUBISHI MICROCOMPUTERS

38C8 Group

Key Input Interrupt (Key-on Wake-Up)

A key input interrupt request is generated by applying “L” level to any

pin of port P2 that have been set to input mode. In other words, it is

generated when AND of input level goes from “1” to “0”. An example

of using a key input interrupt is shown in Figure 15, where an inter-

rupt request is generated by pressing one of the keys consisted as

an active-low key matrix which inputs to ports P20–P23.

Fig. 15 Connection example when using key input interrupt and port P2 block diagram

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Port P20

latch

Port P21

latch

Port P22

latch

Port P23

latch

Port P24

latch

Port P25

latch

Port P26

latch

Port P27

latch

P20 input

P21 input

P22 input

P23 input

P24 output

P25 output

P26 output

P27 output

PULL register A

Bit 5 = “1”

Port P2

Input reading circuit

Port PXx

“L” level output

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P-channel transistor for pull-up

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CMOS output buffer

Key input interrupt request

Port P27 direction

Port P26 direction

Port P25 direction

Port P24 direction

Port P23 direction

Port P22 direction

Port P21 direction

Port P20 direction

PULL register A

Bit 4 = “1”

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