C8051F54X_14 Datasheet, PDF (198/275 Pages) Silicon Laboratories – Mixed Signal ISP Flash MCU Family

C8051F54x
20.5.1. Write Sequence (Master)
During a write sequence, an SMBus master writes data to a slave device. The master in this transfer will be
a transmitter during the address byte, and a transmitter during all data bytes. The SMBus interface gener-
ates the START condition and transmits the first byte containing the address of the target slave and the
data direction bit. In this case the data direction bit (R/W) will be logic 0 (WRITE). The master then trans-
mits one or more bytes of serial data. After each byte is transmitted, an acknowledge bit is generated by
the slave. The transfer is ended when the STO bit is set and a STOP is generated. Note that the interface
will switch to Master Receiver Mode if SMB0DAT is not written following a Master Transmitter interrupt.
Figure 20.5 shows a typical master write sequence. Two transmit data bytes are shown, though any num-
ber of bytes may be transmitted. Notice that all of the ‘data byte transferred’ interrupts occur after the ACK
cycle in this mode.
S SLA W A Data Byte A Data Byte A P
Interrupts
Received by SMBus
Interface
Transmitted by
SMBus Interface
S = START
P = STOP
A = ACK
W = WRITE
SLA = Slave Address
Figure 20.5. Typical Master Write Sequence
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