Wire Serial I/O Mode Timing - NEC PD789488 User Manual

(2) Communication operation
In 3-wire serial I/O mode, data transmission/reception is performed in 8-bit units.
received bit by bit in synchronization with the serial clock.
Transmit shift register 20 (TXS20/SIO20) and receive shift register 20 (RXS20) shift operations are
performed in synchronization with the fall of the serial clock (SCK20). Then transmit data is held in the SO20
latch and output from the SO20 pin. Also, receive data input to the SI20 pin is latched in receive buffer
register 20 (RXB20/SIO20) on the rise of SCK20.
At the end of an 8-bit transfer, the operation of TXS20/SIO20 and RXS20 stops automatically, and the
interrupt request signal (INTCSI20) is generated.
SIO20
write
SCK20
SO20
Note
SI20
INTCSI20
Note The value of the last bit previously output is output.
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CHAPTER 11 SERIAL INTERFACE 20
Figure 11-11. 3-Wire Serial I/O Mode Timing (1/2)
(i) Master operation timing (CSCK20=0)
1 2 3
DO7 DO6 DO5
DI7 DI6 DI5
User's Manual U15331EJ4V1UD
4 5 6
DO4 DO3 DO2
DI4 DI3 DI2
Data is transmitted/
7 8
DO1 DO0
DI1 DI0