Master Write Sequence
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 generates 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 transmits 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. The interface will switch to Master Receiver Mode if SMB0DAT
is not written following a Master Transmitter interrupt.
Figure 18.5 Typical Master Write Sequence on page 241
write sequence as it appears on the bus, and
Figure 18.6 Master Write Sequence State Diagram (EHACK = 1) on page 242
corresponding firmware state machine. Two transmit data bytes are shown, though any number of bytes may be transmitted. Notice
that all of the “data byte transferred” interrupts occur after the ACK cycle in this mode, regardless of whether hardware ACK generation
is enabled.
a
A
A
A
S
W
P
Data Byte
Data Byte
SLA
S = START
P = STOP
A = ACK
W = WRITE
SLA = Slave Address
Received by SMBus
Interface
Transmitted by
SMBus Interface
Interrupts with Hardware ACK Disabled (EHACK = 0)
Interrupts with Hardware ACK Enabled (EHACK = 1)
a
b
c
d
b
c
d
Figure 18.5. Typical Master Write Sequence
EFM8UB3 Reference Manual
System Management Bus / I2C (SMB0)
silabs.com
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