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CHAPTER 16 SERIAL INTERFACE CHANNEL 0 (
μ
PD780058 Subseries)
(a) Bus release signal (REL)
The bus release signal is a signal with the SB0 (SB1) line which has changed from the low level to the
high level when the SCK0 line is at the high level (without serial clock output).
This signal is output by the master device.
Figure 16-12. Bus Release Signal
The bus release signal indicates that the master device is going to transmit an address to the slave device.
The slave device incorporates hardware to detect the bus release signal.
Caution
The transition of the SB0 (SB1) line from low to high when the SCK0 line is high is
recognized as a bus release signal. If the transition timing of the bus is shifted due to
the influence of board capacitance, transmitted data may be judged as a bus release
signal. Exercise care in wiring so that noise is not superimposed on the signal lines.
(b) Command signal (CMD)
The command signal is a signal with the SB0 (SB1) line which has changed from the high level to the
low level when the SCK0 line is at the high level (without serial clock output). This signal is output by
the master device.
Figure 16-13. Command Signal
The command signal indicates that the master is to transmit a command to the slave (however, the
command signal following the bus release signal indicates that an address is transmitted).
The slave device incorporates hardware to detect the command signal.
Caution
The transition of the SB0 (SB1) line from high to low when the SCK0 line is high is
recognized as a command signal. If the transition timing of the bus is shifted due to the
influence of board capacitance, transmitted data may be judged as a command signal.
Exercise care in wiring so that noise is not superimposed on the signal lines.
SCK0
"H"
SB0 (SB1)
SCK0
"H"
SB0 (SB1)