
346
CHAPTER 15
SERIAL INTERFACE SIO3
User’s Manual U12790EJ2V0UD
SCK3
SI3
SO3
CSIIF3
Transfer starts at falling edge of SCK3
Transfer ends
123
4
5
6
7
8
DI7
DI6
DI5
DO7
DO6
DO5
DI4
DI3
DI2
DO4
DO3
DO2
DI1
DI0
DO1
DO0
(2) Communication operation
In the 3-wire serial I/O mode, data is transmitted or received in 8-bit units. Data is transmitted or received
in synchronization with the serial clock.
The shift operation of serial I/O shift register 3 (SIO3) is performed at the falling edge of the serial clock (SCK3).
The transmit data is held in SO3 and is output from the SO3 pin. The receive data input to the SI3 pin is latched
to SIO3 at the falling edge of the serial clock.
When 8-bit data has been transferred, the operation of SIO3 is automatically stopped, and the interrupt request
flag (CSIIF3) is set.
Figure 15-4. Timing in 3-Wire Serial I/O Mode
(3) Starting transfer
Serial transfer is started by writing (or reading) transfer data to serial I/O shift register 3 (SIO3) when the
following conditions are satisfied.
Operation control bit of SIO3 (bit 7 (CSIE3) of serial operation mode register 3 (CSIM3)) = 1
If the internal serial clock is stopped or SCK3 is high after transfer of 8-bit serial data
Transmit/receive mode
Transfer is started if SIO3 is written when bit 7 (CSIE3) of CSIM3 = 1, and bit 2 (MODE) = 0
Receive mode
Transfer is started if SIO3 is read when bit 7 (CSIE3) of CSIM3 = 1, and bit 2 (MODE) = 1
Caution
Serial transfer is not started even if 1 is written to CSIE3 after data is written to SIO3.
On completion of transfer of the 8-bit data, serial transfer is automatically stopped, and the interrupt request
flag (CSIIF3) is set.