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SINGLE-CHIP 8-BIT CMOS MICROCOMPUTER
MITSUBISHI MICROCOMPUTERS
7560 Group
32
SERIAL I/O
Serial I/O1
Serial I/O1 can be used as either clock synchronous or asynchro-
nous (UART) serial I/O. A dedicated timer (baud rate generator) is
also provided for baud rate generation.
(1) Clock Synchronous Serial I/O Mode
Clock synchronous serial I/O mode is selected by setting the se-
rial I/O1 mode selection bit of the serial I/O1 control register to
“
1
”
.
For clock synchronous serial I/O mode, the transmitter and the re-
ceiver must use the same clock as an operation clock.
When an internal clock is selected as an operation clock, transmit
or receive is started by a write signal to the transmit buffer regis-
ter.
When an external clock is selected as an operation clock, serial I/
O1 becomes the state where transmit or receive can be performed
by a write signal to the transmit buffer register. Transmit and re-
ceive are started by input of an external clock.
Fig. 28 Block diagram of clock synchronous serial I/O1
Fig. 29 Operation of clock synchronous serial I/O1 function
P
4
6
/
S
C
L
K
1
P
4
7
/
S
R
D
Y
1
P
4
4
/
R
X
D
P4
5
/T
X
D
X
I
N
1
/
4
1/4
F
/
F
Serial I/O1 status register
Serial I/O1 control register
R
e
c
e
i
v
e
b
u
f
f
e
r
r
e
g
i
s
t
e
r
A
d
d
r
e
s
s
0
0
1
8
1
6
Receive shift register
Receive buffer full flag (RBF)
R
e
c
e
i
v
e
i
n
t
e
r
r
u
p
t
r
e
q
u
e
s
t
Receive clock control circuit
S
h
i
f
t
c
l
o
c
k
Serial I/O1 synchronous
clock selection bit
Frequency division ratio 1/(n+1)
Baud rate generator
A
d
d
r
e
s
s
0
0
1
C
1
6
BRG count source selection bit
F
a
l
l
i
n
g
-
e
d
g
e
d
e
t
e
c
t
o
r
Data bus
Address 0018
16
S
h
i
f
t
c
l
o
c
k
Transmit shift register shift completion flag (TSC)
Transmit interrupt source selection bit
Transmit buffer empty flag (TBE)
Address 0019
16
T
r
a
n
s
m
i
t
i
n
t
e
r
r
u
p
t
r
e
q
u
e
s
t
Data bus
A
d
d
r
e
s
s
0
0
1
A
1
6
T
r
a
n
s
m
i
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b
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r
r
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r
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r
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m
i
t
cl
o
c
k
c
o
n
t
r
o
l
c
i
r
c
u
i
t
Receive enable signal S
RDY1
D
7
D
0
D
1
D
2
D
3
D
4
D
5
D
6
RBF =
“
1
”
TSC =
“
1
”
v
e
r
r
u
d
e
t
e
c
t
TBE =
“
0
”
TBE =
“
1
”
TSC =
“
0
”
T
(
c
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1
a
/
2
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(
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)
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s 1
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.
=
:
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s
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n
r
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m
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“
0
”
,
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i
3
:
r
a
r
q
e
u
d
e
(
s
T
t
S
f
C
a
c
t
o
r
1
b
”
e
)
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t
w
b
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s
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t
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p
n
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b
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t
(
(
T
T
I
B
C
E
)
o
=
f
“
t
1
h
”
e
)
s
o
r
r
t
=
“
y
t
n
i
u
i
e
i
a
l
4
e
i
n
t
e
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r
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p
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q
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t
o
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c
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w
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r
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c
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v
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b
u
f
f
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r
f
u
l
l
f
l
a
g
(
R
B
F
)
b
e
c
o
m
e
s
“
1
”
.
D
7
D
0
D
1
D
2
D
3
D
4
D
5
D
6
(N
o
t
e
1
)
(Note 3)
(Note 2)
(Note 3)
(Note 4)