M3885 datasheet(25/103 Pages) RENESAS

25 / 103 page

3885 Group

SINGLE-CHIP 8-BIT CMOS MICROCOMPUTER

MITSUBISHI MICROCOMPUTERS

Fig. 18 Connection example when using key input interrupt and port P3 block diagram

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✻✻

✻

✻✻

✻

✻✻

✻

✻✻

✻

✻✻

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✻✻

Port P30

latch

Port P30

direction register = “0”

Port P31

latch

Port P31

direction register = “0”

Port P32

latch

Port P32

direction register = “0”

Port P33

latch

Port P33

direction register = “0”

Port P34

latch

Port P34

direction register = “1”

Port P35

latch

Port P35

direction register = “1”

Port P36

latch

Port P36

direction register = “1”

Port P37

latch

Port P37

direction register = “1”

P30 input

P31 input

P32 input

P33 input

P34 output

P35 output

P36 output

P37 output

Port control register 1

Bit 5 = “0”

Port P3 input circuit

Comparator circuit

Port PXx

“L” level output

✻ P-channel transistor for pull-up

✻✻ CMOS output buffer

Key input interrupt request

Port control register 1

Bit 4 = “1”

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 the logical AND of all port P3 input

goes from “1” to “0”. An example of using a key input interrupt is

shown in Figure 18, where an interrupt request is generated by

pressing one of the keys consisted as an active-low key matrix

which inputs to ports P30–P33.

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