Electronics America Single-Chip Microcontrollers User's Manual

CHAPTER 11 SERIAL INTERFACE 20
User’s Manual U15331EJ4V1UD 215
Figure 11-11. 3-Wire Serial I/O Mode Timing (2/2)
(ii) Slave operation timing (CSCK20=1)
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DI7 DI6 DI5 DI4 DI3 DI2 DI1 DI0
DO7 DO6 DO5 DO4 DO3 DO2 DO1 DO0
SCK20
SI20
NoteSO20
SIO20
write
INTCSI20
Note The value of the last bit previously output is output.
(3) Transfer start
Serial transfer is started by setting transfer data to transmit shift register 20 (TXS20/SIO20) when the
following two conditions are satisfied.
• Bit 7 (CSIE20) of serial operation mode register 20 (CSIM20) = 1
• Internal serial clock is stopped or SCK20 is high after 8-bit serial transfer.
Caution If CSIE20 is set to “1” after data is written to TXS20/SIO20, transfer does not start.
Termination of 8-bit transfer stops the serial transfer automatically and generates the interrupt request signal
(INTCSI20).