
24
SINGLE-CHIP 8-BIT CMOS MICROCOMPUTER
3822 Group
MITSUBISHI MICROCOMPUTERS
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 20, 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. 20 Connection example when using key input interrupt and port P2 block diagram
P
o
r
t
P
XX
“
L
”
l
e
v
e
l
o
u
t
p
u
t
Port P2
7
direction register = “1”
P
2
7
o
u
t
p
u
t
P2
6
output
PULL register A bit 2 = “1”
P
2
5
o
u
t
p
u
t
P
2
4
o
u
t
p
u
t
P
2
3
i
n
p
u
t
P
o
r
t
P
2
6
l
a
t
c
h
P
o
r
t
P
2
5
l
a
t
c
h
P
o
r
t
P
2
4
l
a
t
c
h
Port P2
3
latch
P
o
r
t
P
2
7
l
a
t
c
h
P
o
r
t
P
2
5
d
i
r
e
c
t
i
o
n
r
e
g
i
s
t
e
r
=
“
1
”
Port P2
4
direction register = “1”
Port P2
3
direction register = “0”
P2
2
input
P
2
1
i
n
p
u
t
P
2
0
i
n
p
u
t
P
o
r
t
P
2
2
l
a
t
c
h
P
o
r
t
P
2
1
l
a
t
c
h
Port P2
0
latch
P
o
r
t
P
2
2
d
i
r
e
c
t
i
o
n
r
e
g
i
s
t
e
r
=
“
0
”
P
o
r
t
P
2
1
d
i
r
e
c
t
i
o
n
r
e
g
i
s
t
e
r
=
“
0
”
Port P2
0
direction register = “0”
P
o
r
t
P
2
I
n
p
u
t
r
e
a
d
i
n
g
c
i
r
c
u
i
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
6
d
i
r
e
c
t
i
o
n
r
e
g
i
s
t
e
r
=
“
1
”
✽
✽
✽
✽✽
✽
✽✽
✽
✽✽
✽
✽✽
✽
✽✽
✽
✽✽
✽
✽✽
Kommentare zu diesen Handbüchern