CHAPTER 15 SERIAL INTERFACE CHANNEL 1
257
(3) Communication operation
(a) Basic transmission/reception mode
This transmission/reception mode is the same as the 3-wire serial I/O mode in which specified number
of data are transmitted/received in 8-bit units.
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 the CSIIF1.
If busy control and strobe control are not executed, the P23/STB and P24/BUSY pins can be used as
normal input/output ports.
Figure 15-8 shows the basic transmission/reception mode operation timings, Figure 15-9 shows the
operation flowchart. The operation of the buffer RAM in 6-byte transmission/reception mode is shown
in Figure 15-10.
Figure 15-8. Basic Transmission/Reception Mode Operation Timings
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
Cautions 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 till 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 the
automatic data transmit/receive interval specify register (ADTI) (see (5) Automatic
data transmit/receive interval).
When TRF is cleared, SO1 pin becomes low level.
2.
Remarks 1.
CSIIF1: Interrupt request flag
2.
TRF: Bit 3 of the automatic data transmit/receive control register (ADTC)