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CHAPTER 14 SERIAL INTERFACE (SIO3)
Preliminary User’s Manual U16035EJ1V0UM
(2) Communication operations
In the 3-wire serial I/O mode, data is transmitted and received in 8-bit units. Each bit of data is transmitted or
received in synchronization with the serial clock.
The serial I/O shift register 3n (SIO3n) is shifted in synchronization with the falling edge of the serial clock.
Transmission data is held in the SO3n latch and is output from the SO3n pin. Data that is received via the SI3n
pin in synchronization with the rising edge of the serial clock is latched to SIO3n.
Completion of an 8-bit transfer automatically stops operation of SIO3n and sets interrupt request flag (CSIIF3n).
Figure 14-4. Timing of 3-Wire Serial I/O Mode
Remark
n = 0, 1
(3) Transfer start
A serial transfer starts when the following two conditions have been satisfied and transfer data has been set (or
read) to serial I/O shift register 3n (SIO3n).
• SIO3n operation control bit (CSIE3n) = 1
• After an 8-bit serial transfer, either the internal serial clock is stopped or SCK3n is set to high level.
• Transmit/transmit and receive mode
When CSIE3n = 1 and MODEn = 0, transfer starts when writing to SIO3n.
• Receive-only mode
When CSIE3n = 1 and MODEn = 1, transfer starts when reading from SIO3n.
Caution
After data has been written to SIO3n, transfer will not start even if the CSIE3n bit value is set
to “1”.
Completion of an 8-bit transfer automatically stops the serial transfer operation and interrupt request flag
(CSIIF3n) is set.
Remark
n = 0, 1
SI3n
DI7
DI6
DI5
DI4
DI3
DI2
DI1
DI0
CSIIF3n
SCK3n
1
SO3n
DO7
DO6
DO5
DO4
DO3
DO2
DO1
DO0
2
3
4
5
6
7
8
Transfer completion
Transfer starts in synchronization with the SCK3n falling edge
