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CHAPTER 15 SERIAL INTERFACE CHANNEL 0 (
μ
PD78018F SUBSERIES)
SCK0
"H"
SB0 (SB1)
(a) Bus release signal (REL)
The bus release signal is the positive transition signal of the SB0 (SB1) line, i.e., transition from the low
to high level, when the SCK0 line is high (when the serial clock is not output).
This signal is output by the master.
Figure 15-11. Bus Release Signal
The bus release signal indicates that the master is to transmit an address to the slave. The slave is
provided with hardware that detects the bus release signal.
Caution
A positive transition of the SB0 (SB1) pin from low to high is recognized as a bus release
signal when the SCK0 line is high. If the change timing of the bus is shifted due to the
influence of the board capacitance, data that is transmitted may be identified as bus
release signal by mistake. Exercise care in wiring.
(b) Command signal (CMD)
The command signal is the negative transition signal of the SB0 (SB1) line, i.e., transition from the high
to low level, when the SCK0 line is high (when the serial clock is not output). This signal is output by
the master.
Figure 15-12. Command Signal
The command signal indicates that the master is going to transmit a command to the slave (however,
the command signal following the bus release signal indicates that an address is to be transmitted).
The slave is provided with hardware that detects the command signal.
Caution
A positive transition of the SB0 (SB1) pin from high to low is recognized as a command
signal when the SCK0 line is high. If the change timing of the bus is shifted due to the
influence of the board capacitance, data that is transmitted may be identified as
command signal by mistake. Exercise care in wiring.
SCK0
"H"
SB0 (SB1)