
7542 Group
Rev.3.02 Oct 31, 2006 Page 46 of 134
REJ03B0006-0302
Fig. 52 Block diagram of clock synchronous serial I/O1
Fig. 53 Operation of clock synchronous serial I/O1 function
Serial I/O
The 7542 Group has Serial I/O1 and Serial I/O2. Except that Serial
I/O1 has the bus collision detection function and the T
X
D
2
output
structure for Serial I/O2 is CMOS only, they have the same function.
●
Serial I/O1
Serial I/O1 can be used as either clock synchronous or asynchro-
nous (UART) serial I/O. A dedicated timer is also provided for
baud rate generation.
(1) Clock Synchronous Serial I/O1 Mode
Clock synchronous serial I/O1 mode can be selected by setting
the serial I/O1 mode selection bit of the serial I/O1 control register
(bit 6) to “1”.
For clock synchronous serial I/O1, the transmitter and the receiver
must use the same clock. If an internal clock is used, transfer is
started by a write signal to the TB/RB.
1
/
4
1
/
4
F
/
F
P
1
2
/
S
C
L
K
1
S
e
r
i
a
l
I
/
O
1
s
t
a
t
u
s
r
e
g
i
s
t
e
r
Serial I/O1 control register
P
1
3
/
S
R
D
Y
1
P
1
0
/
R
X
D
1
/
C
A
P
0
P
1
1
/
T
X
D
1
X
IN
Receive buffer register 1
A
d
d
r
e
s
s
0
0
1
8
1
6
R
e
c
e
i
v
e
s
h
i
f
t
r
e
g
i
s
t
e
r
1
R
e
c
e
i
v
e
b
u
f
f
e
r
f
u
l
l
f
l
a
g
(
R
B
F
)
Receive interrupt request (RI)
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 1
Address 001C
16
BRG count source selection bit
C
l
o
c
k
c
o
n
t
r
o
l
c
i
r
c
u
i
t
Falling-edge detector
T
r
a
n
s
m
i
t
b
u
f
f
e
r
r
e
g
i
s
t
e
r
1
Data bus
A
d
d
r
e
s
s
0
0
1
8
1
6
Shift clock
T
r
a
n
s
m
i
t
s
h
i
f
t
c
o
m
p
l
e
t
i
o
n
f
l
a
g
(
T
S
C
)
T
r
a
n
s
m
i
t
b
u
f
f
e
r
e
m
p
t
y
f
l
a
g
(
T
B
E
)
T
r
a
n
s
m
i
t
i
n
t
e
r
r
u
p
t
r
e
q
u
e
s
t
(
T
I
)
Transmit interrupt source selection bit
Address 0019
16
Data bus
A
d
d
r
e
s
s
0
0
1
A
1
6
Transmit shift register 1
D
7
D
7
D
0
D
1
D
2
D
3
D
4
D
5
D
6
D
0
D
1
D
2
D
3
D
4
D
5
D
6
RBF = 1
TSC = 1
TBE = 0
TBE = 1
TSC = 0
Transfer shift clock
(1/2 to 1/2048 of the internal
clock, or an external clock)
Serial output TxD
1
Serial input RxD
1
Write pulse to receive/transmit
buffer register 1 (address 0018
16
)
Overrun error (OE)
detection
Notes 1: As the transmit interrupt (TI), which can be selected, either when the transmit buffer has emptied (TBE=1) or after
the transmit shift operation has ended (TSC=1), by setting the transmit interrupt source selection bit (TIC) of the
serial I/O1 control register.
2: If data is written to the transmit buffer register when TSC=0, the transmit clock is generated continuously and serial
data is output continuously from the TxD
1
pin.
3: The receive interrupt (RI) is set when the receive buffer full flag (RBF) becomes “1” .
Receive enable signal
S
RDY1