Sbi Communication And Signals; Sbi Transfer Timing; Bus Release Signal - NEC PD78212 User Manual

10.6 SBI COMMUNICATION AND SIGNALS

This section describes the format of the SBI serial data and signals to be used.
Serial data transferred via SBI can be divided into three groups: address, command, and data. Each frame of serial
data is formed as shown below:
(bus release signal) + (command signal) + 8-bit data + ACK + (BUSY)
Fig. 10-13 shows the transfer timing of the address, command, and data.
Address transfer
SCK
SB0

Bus release signal

Command transfer
SCK
SB0
Data transfer
SCK
SB0
The master device outputs the bus release signal and command signal. The slave device outputs BUSY. Either
the master or slave device can output ACK. (Usually, the device receiving 8-bit data outputs ACK.)
The master device continues serial clock output during the period from the start of 8-bit data transfer to the release
of BUSY.
10.6.1 Bus Release Signal (REL)
The bus release signal is the SB0 line going from low to high while the SCK line is high (the serial clock is not
output). The master device outputs this signal.
The bus release signal indicates that the master device is going to send an address to a slave device. The slave
device contains hardware to detect the bus release signal.
Chapter 10 Clock Synchronous Serial Interface
Fig. 10-13 SBI Transfer Timing
A7
Command signal
C7
D7
Fig. 10-14 Bus Release Signal
SCK
"H"
SB0
8 9
A0 ACK BUSY
9
C0 ACK BUSY READY
8 9
D0 ACK BUSY READY
10
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