NEC PD78F9488 - Manual (Page 236)

CHAPTER 12 SERIAL INTERFACE 1A0
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User’s Manual U15331EJ4V1UD
(3) Communication operation
(a) Basic transmit/receive mode
This transmit/receive mode is the same as the 3-wire serial I/O mode in which the specified number of
data are transmitted/received in 8-bit units.
Serial transfer is started when any data is written to serial I/O shift register 1A0 (SIO1A0) while bit 7
(CSIE10) of serial operation mode register 1A0 (CSIM1A0) is set to 1.
Upon completion of transmission of the last byte, the interrupt request flag (CSIIF10) is set. The
termination of automatic transmission/reception should be checked by using bit 3 (TRF0) of automatic
data transmit/receive control register 0 (ADTC0), not by CSIIF10 because CSIIF10 of the interrupt
request flag is cleared if an interrupt is acknowledged.
Figure 12-7 shows the basic transmit/receive mode operation timing, and Figure 12-8 shows the
operation flowchart.
Figure 12-9 shows buffer RAM operation at 6-byte transmission.
Figure 12-7. Basic Transmit/Receive Mode Operation Timing
SCK10
SO10 D7 D6 D5 D4 D3 D2 D1 D0 D7 D6 D5 D4 D3 D2 D1 D0
CSIIF10
TRF0
SI10 D7 D6 D5 D4 D3 D2 D1 D0 D7 D6 D5 D4 D3 D2 D1 D0
Interval
Cautions 1. Because, in the basic transmit/receive 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 automatic
data transmit/receive interval specification register 0 (ADTI0) (refer to 12.4.3 (5)
Interval time of automatic transmission/reception).
2. When TRF0 is cleared, the SO10 pin becomes low level.
Remark CSIIF10: Interrupt request flag
TRF0: Bit 3 of automatic data transmit/receive control register 0 (ADTC0)