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CHAPTER 17 SERIAL INTERFACE CHANNEL 1
(3) Communication operation
(a) Basic transmit/receive mode
This mode is to execute data transmission/reception in 8-bit units by the specified number of times, like
in the 3-wire serial I/O mode.
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.
When the last byte has been completely transmitted, an interrupt request flag (CSIIF1) is set. 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 busy or strobe control is not performed, the P23/STB and P24/BUSY pins can be used as ordinary
I/O port pins.
Figure 17-8 shows the operation timing of the basic transmit/receive mode, and Figure 17-9 shows an
operation flowchart. The buffer RAM operation when six bytes are transmitted/received is shown in Figure
17-10.
Figure 17-8. Operation Timing of Basic Transmit/Receive Mode
Cautions 1. In the basic transmit/receive mode, the buffer RAM is written/read after 1-byte data
has been transmitted/received. Therefore, there is interval time until the next
transmission/reception is executed. Because the buffer RAM is written/read simul-
taneously with the CPU processing, the maximum interval time depends on the CPU
processing and a value of the automatic data transmit/receive 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
SI1
D7 D6 D5 D4 D3 D2 D1 D0
D7 D6 D5 D4 D3 D2 D1 D0
Interval