
CHAPTER 15 SERIAL INTERFACE CHANNEL 1
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(c) Repeat transmission mode
In this mode, data stored in the buffer RAM is transmitted repeatedly.
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.
Unlike the basic transmission mode, after the last byte (data in address FAC0H) has been transmitted,
the interrupt request flag (CSIIF1) is not set, the value at the time when the transmit function was started
is set in the automatic data transmit/receive address pointer (ADTP) again, and the buffer RAM contents
are transmitted again.
When a reception operation, busy control and strobe control are not performed, the P20/SI1, P23/STB
and P24/BUSY pins can be used as normal input/output ports.
The repeat transmission mode operation timing is shown in Figure 15-14, and the operation flowchart
in Figure 15-15. The operation of the buffer RAM in 6-byte repeat transmission mode is shown in Figure
15-16.
Figure 15-14. Repeat Transmission Mode Operation Timings
D7 D6 D5 D4 D3 D2 D1 D0
D7 D6 D5 D4 D3 D2 D1 D0
Interval
Interval
D7 D6 D5
SCK1
SO1
Caution
Since, in the repeat transmission mode, a read is performed on the buffer RAM after
the transmission of one byte, the interval is included in the period up to the next
transmission. As the buffer RAM read is performed at the same time as CPU
processing, the maximum interval is dependent upon the CPU operation and the value
of the automatic data transmit/receive interval specify register (ADTI) (see (5) Automatic
data transmit/receive interval).