NEC 78014Y Series User Manual page 426

(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 specified number of data are
transmitted/received in 8-bit units.
Serial transfer starts when any data is written to the serial I/O shift register 1 (SIO1) while the serial operating
mode register 1 (CSIM1) bit 7 (CSIE1) is set to 1.
Upon completion of transmission of the last byte, the interrupt request flag (CSIIF1) is set. However, the
termination of automatic transmission/reception should be judged by using bit 3 (TRF) of the automatic data
transmit/receive control register (ADTC), not 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 17-7 shows the basic transmit/receive mode operation timings, and Figure 17-8 shows the operation
flowchart. In addition, Figure 17-9 shows the buffer RAM operation in 6-byte transmission/reception.
SCK1
SO1
SI1
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CSIIF1
TRF
Cautions 1. Because, in the basic transmit/receive mode, the automatic transmit/receive function
Remark CSIIF1 : Interrupt request flag
426
CHAPTER 17 SERIAL INTERFACE CHANNEL 1
Figure 17-7. Basic Transmit/Receive Mode Operation Timings
D7 D6 D5 D4 D3 D2 D1 D0
D7 D6 D5 D4 D3 D2 D1 D0
writes/reads data to/from the buffer RAM after 1-byte transmission/reception, an
interval is inserted until 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 (see (5) Automatic data
transmit/receive interval).
2. When TRF is cleared, the SO1 pin becomes low.
TRF : Bit 3 of the automatic data transmit/receive control register (ADTC)
Interval
D7 D6 D5 D4 D3 D2 D1 D0
D7 D6 D5 D4 D3 D2 D1 D0