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CHAPTER 18 SERIAL INTERFACE CHANNEL 1
(b) Basic transmission mode
In this mode, the specified number of 8-bit unit data are transmitted.
Serial transmission is started by writing the desired data to serial I/O shift register 1 (SIO1) when bit 7
(CSIE1) of serial operation mode register 1 (CSIM1) is set at 1.
When the final byte has been sent, an interrupt request flag (CSIIF1) is set. However, judge the termination
of auto send and receive, not by CSIIF1 (interrupt request flag) but by bit 3 (TRF) of the auto data send
and receive control register (ADTC).
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/ports.
Figure 18-11 shows the basic transmission mode operation timings, and Figure 18-12 shows the operation
flowchart. Figure 18-13 shows the operation of the internal buffer RAM when 6 bytes of data are
transmitted or received.
Figure 18-11. Basic Transmission Mode Operation Timings
SCK1
SO1 D7 D6 D5 D4 D3 D2 D1 D0 D7 D6 D5 D4 D3 D2 D1 D0
CSIIF1
TRF
Interval
Cautions 1. Because, in the basic transmission mode, the automatic transmit/receive function
reads data from the internal buffer RAM after 1-byte transmission, an interval is
inserted till the next transmission. As the internal 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 specify
register (ADTI) (see (5) "Automatic transmit/receive interval time").
2. When TRF is cleared, the SO1 pin becomes low level.
CSIIF1: Interrupt request flag
TRF : Bit 3 of the auto data send and receive control register (ADTC)