NEC uPD78056Y User Manual
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CHAPTER 18 SERIAL INTERFACE CHANNEL 1
(2) Communication operation
The 3-wire serial I/O mode is used for data transmission/reception in 8-bit units. Bit-wise data transmission/
reception is carried out in synchronization with the serial clock.
Shift operation of the serial I/O shift register 1 (SIO1) is carried out at the falling edge of the serial clock SCK1.
The transmit data is held in the SO1 latch and is output from the SO1 pin. The receive data input to the SI1
pin is latched into SIO1 at the rising edge of SCK1.
Upon termination of 8-bit transfer, the SIO1 operation stops automatically and the interrupt request flag
(CSIIF1) is set.
Figure 18-6. 3-Wire Serial I/O Mode Timings
Caution
SO1 pin becomes low level by SIO1 write.
SI1
SCK1
1
2
3
4
5
6
7
8
DI7
DI6
DI5
DI4
DI3
DI2
DI1
DI0
SO1
DO7
DO6
DO5
DO4
DO3
DO2
DO1
DO0
CSIIF1
Transfer Start at the Falling Edge of SCK1
End of Transfer
SIO1 Write