S
Device Addr
Wr
A
Command
A
Byte #0
A
Byte #1
A
PEC
A
P
S
Device Addr
Wr
A
Command
A
Byte #0
A
Byte #1
A
P
S
Device Addr
Wr
A
Command
A
Byte #0
A
PEC
A
P
S
Device Addr
Wr
A
Command
A
Byte #0
A
P
Master Mode Operation Reference
374
SNIU028A – February 2016 – Revised April 2016
Copyright © 2016, Texas Instruments Incorporated
PMBus Interface/I2C Interface
After programming the Master Control Register, the PMBus Interface initiates a Receive Byte message
onto the PMBus. The firmware can wait for an End of Message interrupt from the PMBus Interface to
verify the accuracy of the message transmission. Upon receipt of the EOM interrupt, the Status Register is
read to verify proper slave acknowledgement of the device address and to determine if any data is
available for reading in the Receive Data Register. If PEC_EN was asserted in the Master Control
Register, the PEC_VALID bit in the Status Register is also checked to ensure a proper PEC byte was
received from the Slave with the received data.
10.7.4 Write Byte/Word
Figure 10-27. Write Byte w/o PEC Byte
Figure 10-28. Write Byte with PEC Byte
Figure 10-29. Write Word w/o PEC Byte
Figure 10-30. Write Word with PEC Byte
The Write Byte and Write Word messages consist of a device address, a command byte, transmitted data
bytes and an optional PEC byte. Write Byte messages include a single byte, while the Write Word
messages support transmission of 2 bytes to the corresponding slave module. Similar to the Send Byte
protocol, the Master Control Register is configured to send 1 or 2 bytes, the CMD_EN bit is set to enable
command byte transmission and the optional PEC_EN bit is set.
With the command byte transmission enabled, the format of the Transmit Data Register differs from the
Send Byte protocol. In Bits 7-0 of the Transmit Data Register, the firmware must program the command
byte to be sent to the slave. The data byte(s) are programmed into bits 15-8 and bits 23-16.
After programming the Master Control Register, the PMBus Interface initiates a Write Byte/Word message
on the PMBus. The firmware can wait for an End of Message interrupt from the interface to verify the
accuracy of the message transmission. The Status Register indicates if the slave acknowledged the
message properly.