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(b) Basic transmission 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.
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 bit 3 (TRF) of the automatic
data transmit/receive control register (ADTC), not 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 ports.
Figure 14-11 shows the basic transmission mode operation timing, and Figure 14-12 shows the
operation flowchart. The operation of the buffer RAM to transmit 6-byte data in transmission mode
is shown in Figure 14-13.
Figure 14-11. Basic Transmission Mode Operation Timing
SCK1
SO1
D7 D6 D5 D4 D3 D2 D1 D0
CSIIF1
TRF
Cautions 1. Because, in the basic transmission 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 CPU processing
and the value of the automatic data transmit/receive interval specification
register (ADTI) (see (5) Automatic transmit/receive interval).
2. When TRF is cleared, the SO1 pin becomes low level.
Remark CSIIF1: Interrupt request flag
TRF:
Bit 3 of the automatic data transmit/receive control register (ADTC)
CHAPTER 14 SERIAL INTERFACE CHANNEL 1
Interval
User's Manual U11302EJ4V0UM
D7 D6 D5 D4 D3 D2 D1 D0
283
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