NEC uPD78P078 - Manual (Page 336)

CHAPTER 17 SERIAL INTERFACE CHANNEL 0 (
µ
PD78078 SUBSERIES)
336
SCK0
“H”
SB0 (SB1)
(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 17-12. 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 If the SB0 (SB1) line changes from low level to high level while the SCK0 line is in high
level, this is recognized as a bus release signal. Therefore, if the changing timing of
bus fluctuates because of the substrate capacity, etc., it may be recognized as a bus
release signal even while data is being transmitted. Care should be taken for the wiring.
(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 17-13. Command Signal
The command signal indicates that the master device is going to transmit a command to the slave device
(however, the command signal following a bus release signal indicates that the master device is going
to transmit an address).
The slave device incorporates hardware to detect the command signal.
Caution If the SB0 (SB1) line changes from high level to low level while the SCK0 line is in high
level, this is recognized as a command signal. Therefore, if the changing timing of bus
fluctuates because of the substrate capacity, etc., it may be recognized as a command
signal even while data is being transmitted. Care should be taken for the wiring.
SCK0
“H”
SB0 (SB1)