
19
SINGLE-CHIP 8-BIT CMOS MICROCOMPUTER
MITSUBISHI MICROCOMPUTERS
38C8 Group
Key Input Interrupt (Key-on Wake-Up)
A key input interrupt request is generated by applying “L” level 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 15, where an inter-
rupt request is generated by pressing one of the keys consisted as
an active-low key matrix which inputs to ports P20–P23.
Fig. 15 Connection example when using key input interrupt and port P2 block diagram
✽
✽✽
✽
✽✽
✽
✽✽
✽
✽✽
✽
✽✽
✽
✽✽
✽
✽✽
✽
✽✽
P
o
r
t
P
2
0
l
a
t
c
h
P
o
r
t
P
2
1
l
a
t
c
h
P
o
r
t
P
2
2
l
a
t
c
h
Port P2
3
latch
P
o
r
t
P
2
4
l
a
t
c
h
Port P2
5
latch
Port P2
6
latch
P
o
r
t
P
2
7
l
a
t
c
h
P2
0
input
P
2
1
i
n
p
u
t
P
2
2
i
n
p
u
t
P
2
3
i
n
p
u
t
P
2
4
o
u
t
p
u
t
P
2
5
o
u
t
p
u
t
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
5
=
“
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
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
”
Port P2
6
direction
register = “1”
Port P2
5
direction
register = “1”
Port P2
4
direction
register = “1”
P
o
r
t
P
2
3
d
i
r
e
c
t
i
o
n
r
e
g
i
s
t
e
r
=
“
0
”
Port P2
2
direction
register = “0”
Port P2
1
direction
register = “0”
Port P2
0
direction
register = “0”
PULL register A
Bit 4 = “1”
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