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(b) Basic transmit mode
In this mode, the specified number of 8-bit unit data are transmitted.
Serial transfer starts when any data is written to the serial I/O shift register 1 (SIO1) while the serial operating
mode register 1 (CSIM1) bit 7 (CSIE1) is set to 1.
Upon completion of transmission of the last byte, the interrupt request flag (CSIIF1) is set. However, the
termination of automatic transmission/reception should be judged by using bit 3 (TRF) of the automatic data
transmit/receive control register (ADTC), not CSIIF1.
If receive operation, busy control and strobe control are not executed, the P20/SI1, P23/STB and P24/BUSY
pins can be used as normal input/output ports.
Figure 17-10 shows the basic transmission mode operation timings, and Figure 17-11 shows the operation
flowchart. In addition, Figure 17-12 shows the buffer RAM operation in 6-byte transmission.
SCK1
SO1
CSIIF1
TRF
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Cautions 1. Because, in the basic transmit mode, the automatic transmit/receive function reads
Remark CSIIF1 : Interrupt request flag
430
CHAPTER 17 SERIAL INTERFACE CHANNEL 1
Figure 17-10. Basic Transmit Mode Operation Timings
D7 D6 D5 D4 D3 D2 D1 D0
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 CPU processing (see (5)
Automatic data transmit/receive interval).
2. When TRF is cleared, the SO1 pin becomes low.
TRF
: Bit 3 of the automatic data transmit/receive control register (ADTC)
Interval
D7 D6 D5 D4 D3 D2 D1 D0
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