SNIU028D February 2016 – September 2020 UCD3138 , UCD3138064 , UCD3138064A , UCD3138128 , UCD3138A , UCD3138A64
A Receive Byte message consists of the device address, a single data byte and an optional PEC byte. Data is being read from the slave in a Receive Byte message. To initiate a Receive Byte message, the firmware programs the device address, the R/W bit and the optional PEC_EN into the Master Control Register. The R/W bit is enabled high to indicate a read message type (data transmitted from Slave to Master).
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.