
SINGLE-CHIP 8-BIT CMOS MICROCOMPUTER
MITSUBISHI MICROCOMPUTERS
7560 Group
33
(2) Asynchronous Serial I/O (UART) Mode
Clock asynchronous serial I/O mode (UART) is selected by setting
the serial I/O1 mode selection bit of the serial I/O1 control register
to
“
0
”
.
Eight serial data transfer formats can be selected, and the transfer
formats used by a transmitter and receiver must be identical.
The transmit and receive shift registers each have a buffer regis-
ter, but the two buffers have the same address (0018
16
) in
memory. Since the shift register cannot be written to or read from
directly, transmit data is written to the transmit buffer, and receive
data is read from the receive buffer.
The transmit buffer can also hold the next data to be transmitted
during transmitting, and the receive buffer register can hold re-
ceived one-byte data while the next one-byte data is being re-
ceived.
Fig. 30 Block diagram of UART serial I/O1
Fig. 31 Operation of UART serial I/O1 function
X
IN
1/4
O
r
E
l
e
P
E F
E
1/16
1
/
1
6
Data bus
R
l
e
e
c
c
t
e
o
i
n
v
e
b
i
b
t
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
R
e
e
c
c
e
e
i
i
v
v
e
e
b
i
n
u
t
f
e
f
e
r
r
u
f
p
u
l
l
r
f
e
l
a
q
g
u
e
(
R
s
B
F
)
r
t
t
B
a
u
d
Address 001C
16
r
a
t
e
g
e
n
e
r
a
t
o
r
F
r
e
q
u
e
n
c
y
d
i
v
i
s
i
o
n
r
a
t
i
o
1
/
(
n
+
1
)
S
T
/
S
P
/
P
A
g
e
n
e
r
a
t
o
r
Transmit buffer register
D
a
t
a
b
u
s
T
r
a
n
s
m
i
t
s
h
i
f
t
r
e
g
i
s
t
e
r
Address 0018
16
T
r
a
n
s
m
i
t
s
h
i
f
t
r
e
g
i
s
t
e
r
s
h
i
f
t
c
o
m
p
l
e
t
i
o
n
f
l
a
g
(
T
S
C
)
T
s
r
u
a
r
n
e
s
g
m
i
s
i
e
t
r
b
u
Address 0019
16
f
f
e
r
e
m
p
t
y
f
l
a
g
(
T
B
E
)
Transmit interrupt request
S
T
d
e
t
e
c
t
o
r
SP detector
U
A
R
T
c
o
Address 001B
16
n
t
r
o
l
r
e
g
i
s
t
e
r
Character length selection bit
A
d
d
r
e
s
s
0
0
1
A
1
6
B
R
G
c
o
u
n
t
s
o
u
r
c
e
s
e
l
e
c
t
i
o
n
b
i
t
Transmit interrupt source selection bit
S
e
r
i
a
l
I
/
O
1
s
y
n
c
h
r
o
n
i
z
a
t
i
o
n
c
l
o
c
k
s
e
l
e
c
t
i
o
n
b
i
t
Clock control circuit
C
h
a
r
a
c
t
e
n
g
t
h
s
e
i
7
b
i
t
s
8
b
i
t
s
S
e
r
i
a
l
I
/
O
1
c
o
n
t
r
o
l
r
e
g
i
s
t
e
r
P4
6
/S
CLK1
S
e
r
i
a
l
I
/
O
1
s
t
a
t
t
P4
4
/R
X
D
P4
5
/T
X
D
T
T
S
B
C
E
=
=
“
“
0
1
”
”
R
B
F
=
“
0
”
T
B
E
=
“
0
”
TBE =
“
0
”
R
B
F
=
“
1
”
RBF =
“
1
”
S
T
D
0
D
1
S
P
D
0
D
1
ST
S
P
T
B
E
=
“
1
”
TSC =
“
1
”
ST
D
0
D
1
SP
D
0
D
1
S
T
S
P
Transmit buffer register write signal
Generated at 2nd bit in 2-stop-bit mode
1 start bit
7 or 8 data bits
1 or 0 parity bit
1 or 2 stop bit (s)
1
2
3
:
E
T
S
a
I
r
h
e
f
/
O
r
o
e
l
e
t
e
1
r
f
e
t
t
h
c
l
a
r
t
g
i
a
h
e
o
n
l
d
r
r
o
e
/
s
a
l
t
e
1
r
i
s
r
e
c
a
m
g
t
r
l
i
e
I
i
t
i
s
o
n
c
/
O
s
t
e
o
i
1
i
r
.
c
e
t
f
t
c
u
i
r
a
o
r
s
t
e
n
s
p
e
a
r
m
r
a
t
u
i
t
t
i
t
p
i
o
h
e
t
n
n
s
e
e
h
a
q
r
r
a
m
u
u
s
e
s
t
e
t
t
r
d
i
e
m
o
q
e
e
c
u
d
u
e
(
t
h
r
s
T
a
s
t
S
t
w
o
C
t
h
h
c
=
e
e
u
n
r
“
R
r
1
B
t
h
e
”
)
F
e
c
,
f
r
e
y
l
e
a
g
c
f
a
s
b
i
v
t
t
t
e
e
o
i
n
c
r
o
b
b
g
m
u
e
t
e
f
e
w
e
s
r
e
t
“
f
e
r
a
1
u
n
n
”
l
l
w
s
(
f
a
l
h
m
t
g
e
i
t
1
n
s
(
i
n
t
s
B
e
e
t
o
F
r
r
p
)
t
r
u
b
a
p
b
i
t
c
s
s
f
o
m
o
o
m
i
t
u
r
r
e
b
c
e
s
u
e
c
f
s
e
“
1
f
e
e
p
”
r
l
t
.
i
o
n
)
.
:
:
s
c
r
I
O
e
n
e
v
n
r
r
t
e
p
c
e
c
e
f
t
a
R
t
t
e
n
t
e
t
t
c
n
h
r
c
e
g
i
o
i
s
n
t
e
b
r
i
t
h
(
a
T
s
I
e
)
m
o
p
f
t
t
i
h
e
d
e
s
(
T
e
B
r
i
E
a
=
“
1
”
)
o
r
h
n
b
h
r
e
t
C
l
N
o
t
e
s
S
e
r
i
a
l
o
u
t
p
u
t
T
x
D
S
e
r
i
a
l
i
n
p
u
t
R
x
D
Receive buffer register read signal
Transmit or receive clock
(Notes 1, 2)
(Notes 1, 2)