M38258MCM Datasheet, PDF (20/70 Pages) Mitsubishi Electric Semiconductor – SINGLE-CHIP 8-BIT CMOS MICROCOMPUTER

MITSUBISHI MICROCOMPUTERS
3825 Group
SINGLE-CHIP 8-BIT CMOS MICROCOMPUTER
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 generated when AND of input level goes from
“1” to “0”. An example of using a key input interrupt is shown in
Figure 16, 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.
Port PXx
"L" level output
P27 output
PULL register A
Bit 2 = "1"
Port P27
direction register = "1"
V
V V _{Port P27}
latch
V
P26 output
Port P26
direction register = "1"
V V _{Port P26}
latch
V
P25 output
V
P24 output
Port P25
direction register = "1"
V V _{Port P25}
latch
Port P24
direction register = "1"
V V _{Port P24}
latch
V
P23 input
Port P23
direction register = "0"
V V _{Port P23}
latch
V
P22 input
Port P22
direction register = "0"
V V _{Port P22}
latch
V
P21 input
Port P21
direction register = "0"
V V _{Port P21}
latch
V
P20 input
Port P20
direction register = "0"
V V _{Port P20}
latch
Key input interrupt request
Port P2
Input reading circuit
V P-channel transistor for pull-up
V V CMOS output buffer
Fig. 16 Connection example when using key input interrupt and port P2 block diagram
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