
9
3851 Group
(Built-in 16 KB ROM)
SINGLE-CHIP 8-BIT CMOS MICROCOMPUTER
MITSUBISHI MICROCOMPUTERS
Fig. 7 Port block diagram (1)
(
1
)
P
o
r
t
s
P
0
,
P
1
r
e
c
t
o
n
r
e
i
s
t
e
r
Data bus
Port latch
(2) Port P20
Port X
C
switch bit
Oscillator
P
o
r
t
P
2
1
Data bus
Port latch
r
e
c
t
o
n
r
e
i
s
t
e
r
Port X
C
switch bi
(
3
)
P
o
r
t
P
21
P
o
r
t
X
C
s
w
i
t
c
h
b
i
D
a
t
a
b
u
s P
o
r
t
l
a
t
c
h
r
e
c
t
o
n
r
e
i
s
t
e
r
S
u
b
-
c
l
o
c
k
g
e
n
e
r
a
t
i
n
g
c
i
r
c
u
i
t
i
n
p
u
(
4
)
P
o
r
t
P
2
2
D
a
t
a
b
u
s
Port latch
rect
on
re
ister
S
D
A
o
u
t
p
u
t
I C-BUS interface enable bi
SDA/SCL pin selection bi
SDA inpu
2
(5) Port P2
3
D
a
t
a
b
u
s
Port latch
r
e
c
t
o
n
r
e
i
s
t
e
r
S
C
L
o
u
t
p
u
I C-BUS interface enable bi
SDA/SCL pin selection bi
SCL inpu
2
(
6
)
P
o
r
t
P
2
4
Data bus
Port latch
rect
on
re
ister
S
D
A
o
u
t
p
u
t
Serial I/O enable bit
Receive enable bi
I
C
-
B
U
S
i
n
t
e
r
f
a
c
e
e
n
a
b
l
e
b
i
SDA/SCL pin selection bi
2
SDA inpu
S
e
r
i
a
l
I
/
O
i
n
p
u
t
(7) Port P2
5
D
a
t
a
b
u
s
Port latch
rect
on
re
ister
S
C
L
o
u
t
p
u
I C bus interface enable bi
S
D
A
/
S
C
L
p
i
n
s
e
l
e
c
t
i
o
n
b
i
S
e
r
i
a
l
I
/
O
e
n
a
b
l
e
b
i
t
T
r
a
n
s
m
i
t
e
n
a
b
l
e
b
i
2
SCL inpu
Serial I/O outpu
P
-
c
h
a
n
n
e
l
o
u
t
p
u
t
d
i
s
a
b
l
e
b
i
t
(8) Port P2
6
D
a
t
a
b
u
s
P
o
r
t
l
a
t
c
h
r
e
c
t
o
n
r
e
i
s
t
e
r
S
e
r
i
a
l
c
l
o
c
k
o
u
t
p
u
Serial I/O mode selection bi
S
e
r
i
a
l
I
/
O
e
n
a
b
l
e
b
i
t
Serial I/O enable bit
Serial I/O clock selection bit
E
x
t
e
r
n
a
l
c
l
o
c
k
i
n
p
u
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