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CHAPTER 14
SERIAL INTERFACE SIO1
User’s Manual U12790EJ2V0UD
(b) Basic transmit mode
In this mode, the specified number of 8-bit unit data are transmitted.
Serial transfer is started when any data is written to serial I/O shift register 1 (SIO1) while bit 7 (CSIE1)
of serial operating mode register 1 (CSIM1) is set to 1, and bit 7 (RE) of the automatic data transmit/receive
control register (ADTC) is set to 0.
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 (TRF) of the automatic data transmit/
receive control register (ADTC), not by CSIIF1.
If a receive operation, busy control, and strobe control are not executed, the P20/SI1, P23/STB and P24/
BUSY pins can be used as normal I/O pins.
Figure 14-11 shows the basic transmit mode operation timing, and Figure 14-12 shows the operation
flowchart.
Figure 14-13 shows the buffer RAM operation when repeatedly transmitting 6 bytes.
Figure 14-11. Basic Transmit Mode Operation Timing
Cautions 1. Because, in the basic transmit mode, the automatic transmit/receive function reads
data from the buffer RAM after 1-byte transmission, an interval is inserted until the
next transmission. As the buffer RAM read is performed at the same time as CPU
processing, the maximum interval is dependent upon the CPU processing and the
value of the automatic data transmit/receive interval specification register (ADTI)
(refer to (6) Automatic data transmit/receive interval).
2. When TRF is cleared, the SO1 pin becomes low level.
Remark
CSIIF: Interrupt request flag
TRF:
Bit 3 of the automatic data transmit/receive control register (ADTC)
SCK1
SO1
D7 D6 D5 D4 D3 D2 D1 D0
CSIIF1
TRF
Interval