3820 datasheet(21/67 Pages) RENESAS

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MITSUBISHI MICROCOMPUTERS

3820 Group

SINGLE-CHIP 8-BIT CMOS MICROCOMPUTER

Key Input Interrupt (Key-on Wake Up)

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

any pin of port P3 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 9,

where an interrupt request is generated by pressing one of the

keys consisted as an active-low key matrix which inputs to ports

P20–P23.

Fig. 10 Connection example when using key input interrupt and port P2 block diagram

Port P20

latch

Port P20

direction register = "0"

Port P21

latch

Port P21

direction register = "0"

Port P22

latch

Port P22

direction register = "0"

Port P23

latch

Port P23

direction register = "0"

Port P24

latch

Port P24

direction register = "1"

Port P25

latch

Port P25

direction register = "1"

Port P26

latch

Port P26

direction register = "1"

Port P27

latch

Port P27

direction register = "1"

P20 input

P21 input

P22 input

P23 input

P24 output

P25 output

P26 output

P27 output

PULL register A

Bit 2 = "1"

Port P2

Input reading circuit

Port PXx

"L" level output

V P-channel transistor for pull-up

V V CMOS output buffer

Key input interrupt request

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