3-Wire Serial I/O Mode Timing - NEC 78K0 User Manual

(2) 1-byte transmission/reception communication operation
(a) 1-byte transmission/reception
When bit 7 (CSIAE0) and bit 6 (ATE0) of serial operation mode specification register 0 (CSIMA0) = 1, 0,
respectively, if communication data is written to serial I/O shift register 0 (SIOA0), the data is output via
the SOA0 pin in synchronization with the SCKA0 falling edge, and then input via the SIA0 pin in
synchronization with SCKA0 falling edge, and stored in the SIOA0 register in synchronization with the
rising edge 1 clock later.
Data transmission and data reception can be performed simultaneously.
If only reception is to be performed, communication can only be started by writing a dummy value to the
SIOA0 register.
When communication of 1 byte is complete, an interrupt request signal (INTACSI) is generated.
In 1-byte transmission/reception, the setting of bit 5 (ATM0) of CSIMA0 is invalid.
Be sure to read data after confirming that bit 0 (TSF0) of serial status register 0 (CSIS0) = 0.
SCKA0
SIA0
SOA0
TSF0
ACSIIF
SIOA0 write
Caution The SOA0 pin becomes low level by an SIOA0 write.
CHAPTER 17 SERIAL INTERFACE CSIA0
Figure 17-10. 3-Wire Serial I/O Mode Timing
1 2 3
DI7 DI6 DI5
DO7 DO6 DO5
*
Transfer starts at falling edge of SCKA0
User's Manual U15947EJ2V0UD
4 5 6
DI4 DI3 DI2
DO4 DO3 DO2
7 8
DI1 DI0
DO1 DO0
End of transfer
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