3822 datasheet(21/59 Pages) RENESAS

21 / 59 page

Rev.1.20

Dec 24, 2003

page 21 of 57

3822 Group (A ver.)

Key Input Interrupt (Key-on wake-up)

A Key-on wake-up interrupt request is generated by applying a

falling edge to any pin of port P2 that have been set to input mode.

In other words, it is gener1ated when AND of input level goes from

“1” to “0”. An example of using a key input interrupt is shown in

Figure 17, 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. 17 Connection example when using key input interrupt and port P2 block diagram

Port PXX

“L” level output

Port P27

direction register = “1”

P27 output

P26 output

PULL register A bit 2 = “1”

P25 output

P24 output

P23 input

Port P26

latch

Port P25

latch

Port P24

latch

Port P23

latch

Port P27

latch

Port P25

direction register = “1”

Port P24

direction register = “1”

Port P23

direction register = “0”

P22 input

P21 input

P20 input

Port P22

latch

Port P21

latch

Port P20

latch

Port P22

direction register = “0”

Port P21

direction register = “0”

Port P20

direction register = “0”

Port P2

Input reading circuit

✽ P-channel transistor for pull-up

✽✽ CMOS output buffer

Key input interrupt request

Port P26

direction register = “1”

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