CHAPTER 14 SERIAL INTERFACE CHANNEL 1279User’s Manual U11302EJ4V0UM(3) Communication operation(a) Basic transmission/reception modeThis transmission/reception mode is the same as the 3-wire serial I/O mode in which the specifiednumber of data are transmitted/received in 8-bit units.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 automaticdata transmit/receive control register (ADTC), not CSIIF1.If busy control and strobe control are not executed, the P23/STB and P24/BUSY pins can be usedas normal I/O ports.Figure 14-8 shows the basic transmission/reception mode operation timing, and Figure 14-9 showsthe operation flowchart. The operation of the buffer RAM to transmit/receive 6-byte data is shownin Figure 14-10.Figure 14-8. Basic Transmission/Reception Mode Operation TimingSCK1SO1 D7 D6 D5 D4 D3 D2 D1 D0 D7 D6 D5 D4 D3 D2 D1 D0CSIIF1TRFSI1 D7 D6 D5 D4 D3 D2 D1 D0 D7 D6 D5 D4 D3 D2 D1 D0IntervalCautions 1. Because, in the basic transmission/reception mode, the automatic transmit/receive function writes/reads data to/from the buffer RAM after 1-byte transmission/reception, an interval is inserted until 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 theautomatic 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 flagTRF: Bit 3 of the automatic data transmit/receive control register (ADTC)
