BCM4414xD1E13A2yzz
Command Structure Overview
Write Byte protocol:
The Host always initiates PMBus™ communication with a START bit. All messages are terminated by the Host with a STOP bit. In a write
message, the master sends the slave device address followed by a write bit. Once the slave acknowledges, the master proceeds with the
command code and then similarly the data byte.
1
7
1
1
8
1
8
1
1
S
Slave Address Wr
A
Command Code
A
x = 0
Data Byte
A
x = 0
P
x = 0 x = 0
S
Start Condition
Repeated start Condition
Sr
Rd Read
Wr Write
X
A
P
Indicated that field is required to have the value of x
Acknowledge (bit may be 0 for an ACK or 1 for a NACK)
Stop Condition
From Master to Slave
From Slave to Master
…
Continued next line
Figure 1 — PAGE COMMAND (00h), WRITE BYTE PROTOCOL
Read Byte protocol:
A Read message begins by first sending a Write Command, followed by a REPEATED START Bit and a slave Address. After receiving the
READ bit, the BCM controller begins transmission of the Data responding to the Command. Once the Host receives the requested Data, it
terminates the message with a NACK preceding a stop condition signifying the end of a read transfer.
1
7
1
1
8
1
1
7
1
1
8
1
1
S
Slave Address Wr
A
Command Code
A
x = 0
Sr Slave Address Rd
A
Data Byte
A
x = 1
P
x = 0 x = 0
x = 1 x = 0
Figure 2 — ON_OFF_CONFIG COMMAND (02h), READ BYTE PROTOCOL
BCM® in a VIA Package
Page 28 of 42
Rev 1.5
10/2016
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