
CHAPTER 15 SERIAL INTERFACE CHANNEL 1
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(b) Basic transmission mode
In this mode, a specified number of 8-bit unit data are transmitted.
Serial transfer is started when any data is written to the serial I/O shift register 1 (SIO1) while bit 7
(CSIE1) of the 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. To judge
completion, however, use bit 3 (TRF) of the automatic data transmit/receive control register (ADTC)
instead of CSIIF1.
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/output ports.
Figure 15-11 shows the basic transmission mode operation timings, Figure 15-12 shows the operation
flowchart. The operation of the buffer RAM in 6-byte transmission mode is shown in Figure 15-13.
Figure 15-11. 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 buffer RAM after 1-byte transmission, an interval is inserted
till 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 specify register (ADTI)
(see (5) Automatic data transmit/receive interval).
When TRF is cleared, the SO1 pin becomes low level.
2.
Remark
CSIIF1: Interrupt request flag
TRF: Bit 3 of the automatic data transmit/receive control register (ADTC)