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APPLICATION
2.4 Serial I/O
2.4 Serial I/O
The 4513/4514 Group has a clock-synchronous serial I/O which can be used to transmit and receive 8-bit
data.
This section describes serial I/O functions, related registers, application examples using serial I/O and
notes.
2.4.1 Carrier functions
Serial I/O consists of the serial I/O register SI, serial I/O mode register J1, serial I/O transmit/receive
completion flag SIOF and serial I/O counter.
A clock-synchronous serial I/O uses the shift clock generated by the clock control circuit as a synchronous
clock. Accordingly, the data transmit and receive operations are synchronized with this shift clock.
In transmit operation, data is transmitted bit by bit from the S
of the shift clock.
In receive operation, data is received bit by bit from the S
shift clock.
Note: 4513/4514 Group only supports LSB-first transmission and reception.
Shift clock
When using the internal clock of 4513/4514 Group as a synchronous clock, eight shift clock pulses
are output from the S
clock as a synchronous clock, the clock that is input from the S
Data transfer rate (baudrate)
When using the internal clock, the data transfer rate can be determined by selecting the instruction
clock divided by 4 or 8.
When using an external clock, the clock frequency input to the S
rate.
Figure 2.4.1 shows the serial I/O block diagram.
X
IN
P2
/S
0
CK
P2
/S
1
OUT
P2
/S
2
IN
Fig. 2.4.1 Serial I/O block diagram
2-40
pin when a transfer operation is started. Also, when using some external
CK
Division circuit
MR
3
(divided by 2)
Internal clock
1
generation circuit
0
(divided by 3)
J1
2
1
1/4
0
1/8
S
CK
S
OUT
S
IN
J1
J1
0
1
Note: The output structure of S
4513/4514 Group User's Manual
pin synchronously with the falling edges
OUT
pin synchronously with the rising edges of the
IN
Instruction clock
Serial I/O mode register J1
J1
3
Synchronous
Serial I/O counter (3)
circuit
MSB
Serial I/O register SI (8)
TSIAB
Register B (4)
Register A (4)
and S
pins is N-channel open-drain.
CK
OUT
pin is used as the shift clock.
CK
pin determines the data transfer
CK
J1
J1
J1
2
1
0
Serial I/O interrupt
SIOF
LSB
TABSI
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