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(9) Start of transfer
A serial transfer is started by setting transfer data in serial I/O shift register 0 (SIO0) if the following two conditions
have been satisfied:
• The serial interface channel 0 operation control bit (CSIE0) = 1.
• After an 8-bit serial transfer, the internal serial clock is stopped or SCL is low.
Cautions 1. Setting CSIE0 to 1 after writing data in SIO0 does not initiate transfer operation.
When an 8-bit data transfer ends, serial transfer is stopped automatically and the interrupt request flag (CSIIF0)
is set.
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CHAPTER 16 SERIAL INTERFACE CHANNEL 0 ( µ PD78014Y Subseries)
2. Because the N-ch open-drain output must be set to high-impedance at the time of data
reception, write FFH to the serial I/O shift register 0 (SIO0) in advance. However, when wake-
up function is used (that is, bit 5 (WUP) of serial operating mode register 0 (CSIM0) is set),
do not write FFH to SIO0 before data reception. Without writing FFH to SIO0, the N-ch open-
drain output is always high-impedance state.
3. If data is written to SIO0 while the slave is in the wait state, that data is held. The transfer
is started when SCL is output after the wait state is cleared.
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