Technical information

20
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
P2
0–P23.
Fig. 10 Connection example when using key input interrupt and port P2 block diagram
Port P2 0
latch
Port P2
0
direction register = "0"
Port P2
1
latch
Port P2
1
direction register = "0"
Port P2
2
latch
Port P2
2
direction register = "0"
Port P2
3
latch
Port P2
3
direction register = "0"
Port P2
4
latch
Port P2
4
direction register = "1"
Port P2
5
latch
Port P2
5
direction register = "1"
Port P2
6
latch
Port P2
6
direction register = "1"
Port P2
7
latch
Port P2
7
direction register = "1"
P2
0 input
P2
1 input
P2
2 input
P2
3 input
P2
4 output
P2
5 output
P2
6 output
P2
7 output
PULL register A
Bit 2 = "1"
Port P2
Input reading circuit
Port PXx
"L" level output
✽ P-channel transistor for pull-up
✽ ✽ CMOS output buffer
Key input interrupt request
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