
SINGLE-CHIP 8-BIT CMOS MICROCOMPUTER
MITSUBISHI MICROCOMPUTERS
3825 Group
23
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 18, 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. 18 Connection example when using key input interrupt and port P2 block diagram
✽
✽
✽
✽
✽ ✽
✽
✽
✽
✽
✽
✽
✽
✽
✽
✽
✽
✽
✽
✽
✽
✽
✽
✽
P
o
r
t
P
20
l
a
t
c
h
Port P2
0
direction register = “0”
P
o
r
t
P
2
1
l
a
t
c
h
Port P2
1
direction register = “0”
Port P2
2
latch
Port P2
2
direction register = “0”
P
o
r
t
P
2
3
l
a
t
c
h
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”
P
o
r
t
P
2
6
l
a
t
c
h
P
o
r
t
P
2
6
d
i
r
e
c
t
i
o
n
r
e
g
i
s
t
e
r
=
“
1
”
P
o
r
t
P
2
7
l
a
t
c
h
P
o
r
t
P
2
7
d
i
r
e
c
t
i
o
n
r
e
g
i
s
t
e
r
=
“
1
”
P
2
0
i
n
p
u
t
P2
1 input
P
2
2
i
n
p
u
t
P2
3 input
P2
4 output
P2
5 output
P
2
6
o
u
t
p
u
t
P2
7 output
P
U
L
L
r
e
g
i
s
t
e
r
A
B
i
t
2
=
“
1
”
Port P2
Input reading circuit
P
o
r
t
P
X
x
“
L
”
l
e
v
e
l
o
u
t
p
u
t
✽ P
-
c
h
a
n
n
e
l
t
r
a
n
s
i
s
t
o
r
f
o
r
p
u
l
l
-
u
p
✽
✽
C
M
O
S
o
u
t
p
u
t
b
u
f
f
e
r
K
e
y
i
n
p
u
t
i
n
t
e
r
r
u
p
t
r
e
q
u
e
s
t
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