Electronics America Single-Chip Microcontrollers User's Manual

CHAPTER 12 SERIAL INTERFACE 1A0
User’s Manual U15331EJ4V1UD 227
(2) Communication operation
In 3-wire serial I/O mode, data transmission/reception is performed in 8-bit units. Data is
transmitted/received bit by bit in synchronization with the serial clock.
Serial I/O shift register 1A0 (SIO1A0) shift operations are performed in synchronization with the fall of the
serial clock (SCK10). Then transmit data is held in the SO10 latch and output from the SO10 pin. Also,
receive data input to the SI10 pin is latched in the SIO1A0 on the rise of SCK10.
At the end of an 8-bit transfer, the operation of SIO1A0 stops automatically, and the interrupt request signal
(INTCSI10) is generated.
Figure 12-5. 3-Wire Serial I/O Mode Timing (1/2)
(i) Master operation timing
12345678
DO7 DO6 DO5 DO4 DO3 DO2 DO1 DO0
DI7 DI6 DI5 DI4 DI3 DI2 DI1 DI0
SCK10
SO10
Note
SI10
SIO1A0
write
INTCSI10
Note The value of the last bit previously output is output.