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CHAPTER 18 SERIAL INTERFACE CHANNEL 0 (
µ
PD78078Y Subseries)
(9) Start of transfer
A serial transfer is started by setting transfer data in the 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. Set CSIE0 to 1 before writing data in SIO0. Setting CSIE0 to 1 after writing data in SIO0
does not initiate transfer operation.
2. Because the N-ch open-drain output must be high-impedance state during data reception,
set bit 7 (BSYE) of the serial bus interface control register (SBIC) to 1 before writing FFH
to SIO0.
However, do not write FFH to the SIO0 during data reception when using the wake-up
function (setting the bit 5 (WUP) of the serial operation mode register 0 (CSIM0)). N-ch
open-drain output always enters the high-impedance state even when FFH is not written
to SIO0.
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.
When an 8-bit data transfer ends, serial transfer is stopped automatically and the interrupt request flag (CSIIF0)
is set.