Specifications
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
P
45/
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
R
ece
i
ve
b
u
ff
er
f
u
ll
fl
ag
(RBF)
R
e
c
e
i
v
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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
S
er
i
a
l
I
/
O
1 sync
h
ronous
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 se
l
ect
i
on
bi
t
F
a
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-
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d
g
e
d
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t
o
r
D
ata
b
us
Add
ress 001816
S
h
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c
k
T
ransm
i
t s
hif
t reg
i
ster s
hif
t comp
l
et
i
on
fl
ag
(TSC)
T
ransm
i
t
b
u
ff
er empty
fl
ag
(TBE)
T
r
a
n
s
m
i
t
i
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t
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r
r
u
p
t
r
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t
T
ransm
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i
nterrupt source se
l
ect
i
on
bi
t
Add
ress 001916
D
ata
b
us
A
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d
r
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s
s
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1
A
1
6
T
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R
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i
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i
gna
l
S
RDY1
D
7
D
0
D
1
D
2
D
3
D
4
D
5
D
6
RBF
= “1”
TSC = “1”
TBE
= “0”
TBE
= “1”
TSC = “0”
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(
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E
)
d
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2
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w
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T
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=
“
0
”
,
t
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T
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D
p
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.
3
:
S
e
l
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c
t
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s
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r
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I
/
O
1
t
r
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r
h
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s
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m
p
t
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d
(
T
B
E
=
“
1
”
)
o
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d
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(
T
S
C
=
“
1
”
)
,
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(
T
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)
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I
/
O
1
c
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t
r
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r
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g
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t
e
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.
4
:
T
h
e
s
e
r
i
a
l
I
/
O
1
r
e
c
e
i
v
e
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c
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v
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b
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f
f
e
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
)
(N
ote
3)
(N
ote
2)
(N
ote
3)
(N
ote 4
)