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CHAPTER 14 SERIAL INTERFACE (SIO1)
Preliminary User’s Manual U13420EJ2V0UM00
(3) Communication operation
(a) Basic transmit/receive mode
This transmit/receive mode is the same as the 3-wire serial I/O mode in which a specified number of data
are transmitted/received in 8-bit units.
Serial transfer is started when any data is written to the serial I/O shift register 1 (SIO1) while bit 7 (CSIE10)
of the serial operating mode register 1 (CSIM1) is set to 1.
Upon completion of transmission of the last byte, the interrupt request flag (CSIIF1) is set. The termination
of automatic transmission/reception should be checked by using bit 3 (TRF0) of the automatic data
transmit/receive control register (ADTC0), not by CSIIF1 because CSIIF1 of the interrupt request flag is
cleared if an interrupt is accepted.
If busy control and strobe control are not executed, the P80/STB and P81/BUSY pins can be used as
normal input/output ports.
Figure 14-7 shows the basic transmit/receive mode operation timings, and Figure 14-8 shows the
operation flowchart.
Figure 14-9 shows buffer RAM operation at 6-byte transmission.
Figure 14-7. Basic Transmit/Receive Mode Operation Timings
Cautions
1. Because, in the basic transmit/receive mode, the automatic transmit/receive function
writes/reads data to/from the buffer RAM after 1-byte transmission/reception, an
interval is inserted till the next transmission/reception. As the buffer RAM write/
read is performed at the same time as CPU processing, the maximum interval is
dependent upon CPU processing and the value of the automatic data transmit/
receive interval specification register (ADTI0) (refer to 14.4.3 (6) Automatic data
transmit/receive interval).
2. When TRF0 is cleared, the SO1 pin becomes low level.
Remark
CSIIF1: Interrupt request flag
TRF0: Bit 3 of automatic data transmit/receive control register (ADTC0)
SCK1
SO1
D7 D6 D5 D4 D3 D2 D1 D0
D7 D6 D5 D4 D3 D2 D1 D0
CSIIF1
TRF0
SI1
D7 D6 D5 D4 D3 D2 D1 D0
D7 D6 D5 D4 D3 D2 D1 D0
Interval
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