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(2) Communication operation
The 3-wire serial I/O mode is used for data transmission/reception in 8-bit units. Data transmission/reception
is carried out bit-wise 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.
SCK1
SI1
SO1
CSIIF1
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Write to SIO1
Caution SO1 pin will be low by writing to SIO1.
420
CHAPTER 17 SERIAL INTERFACE CHANNEL 1
Figure 17-5. 3-Wire Serial I/O Mode Timings
1
2
3
DI7
DI6
DI5
DO7
DO6
DO5
Transfer start synchronizing with the falling edge of SCK1
4
5
6
DI4
DI3
DI2
DO4
DO3
DO2
7
8
DI1
DI0
DO1
DO0
End of Transfer
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