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CHAPTER 17 SERIAL INTERFACE CHANNEL 1
(b) Basic transmit mode
This mode is to execute data transmission in 8-bit units by the specified number of times.
Serial transfer is started by writing any data to the serial I/O shift register 1 (SIO1) when the bit 7 (CSIE1)
of the serial operation mode register 1 (CSIM1) is set to 1.
The interrupt request flag (CSIIF1) is set when the last byte has been completely transmitted. Note,
however, that the completion of automatic transmission/reception should be determined with the bit 3
(TRF) of the automatic transmit/receive control register (ADTC), instead of CSIIF1.
When receive operation, busy control, and strobe control are not performed, the P20/SI1, P23/STB, and
P24/BUSY pins can be used as ordinary I/O ports.
Figure 17-11 shows the operation timing of the basic transmit mode, and Figure 17-12 shows an operation
flowchart.
Figure 17-13 shows the operation of the buffer RAM when 6 bytes are transmitted.
Figure 17-11. Operation Timing of Basic Transmit Mode
Cautions 1. In the basic transmit mode, the buffer RAM is read after 1-byte data has been
transmitted. Therefore, there is an interval time until the next transmission is
executed. Because the buffer RAM is read simultaneously with the CPU processing,
the maximum interval time depends on the CPU processing and a value of the
automatic data transmission/reception time interval specification register (ADTI)
(refer to (5) Interval time of automatic transmission/reception).
2. When TRF is cleared, the SO1 pin goes low.
Remark
CSIIF1: Interrupt request flag
TRF
: Bit 3 of the automatic transmit/receive control register (ADTC)
SCK1
SO1
D7 D6 D5 D4 D3 D2 D1 D0
D7 D6 D5 D4 D3 D2 D1 D0
CSIIF1
TRF
Interval