NEC PD78214 - Manual (Page 307)

278
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PD78214 Sub-Series
10.6.2 Command Signal (CMD)
The command signal is the SB0 line going from high to low while the SCK line is high (the serial clock is not output).
The master device outputs this signal.
Fig. 10-15 Command Signal
SCK
SB0
"H"
The slave device contains the hardware to detect the command signal.
10.6.3 Address
The master device outputs an address, which is 8-bit data, to select one of the slave devices connected to the bus
line.
Fig. 10-16 Address
SCK
SB0
1 2 3 4 5 6 7 8
Address
A7 A6 A5 A4 A3 A2 A1 A0
Command signal
Bus release signal
The 8-bit data output following the bus release signal and command signal is defined as an address. In a slave
device, the hardware detects the condition and the hardware or software checks whether the 8-bit data matches
its own number (slave address). If the 8-bit data matches a slave address, the slave device is selected. This slave
device communicates with the master device until the slave is disconnected from the master.
Fig. 10-17 Selecting a Slave Device by Its Address
Master
Sends address for
slave 2
Slave 1 Not selected
Slave 2 Selected
Slave 3 Not selected
Slave 4 Not selected