SPRUII0F May 2019 – June 2024 TMS320F28384D , TMS320F28384D-Q1 , TMS320F28384S , TMS320F28384S-Q1 , TMS320F28386D , TMS320F28386D-Q1 , TMS320F28386S , TMS320F28386S-Q1 , TMS320F28388D , TMS320F28388S
This section describes some of the message types for PMBus and how to determine which message type is being received in slave mode. This section is oriented toward the most efficient mode of operation – with automatic address and command acknowledgment and is also oriented toward having Packet Error Checking (PEC) enabled.
If automatic address acknowledgment is disabled, all messages start by setting the SLAVE_ADDR_READY bit high. Read commands have two instructions one for the read and one for the write. If automatic command acknowledgment is enabled, the DATA READY bit is set high, as well. If the message has no PEC, the number of bytes available is n-1. For example with PEC, a QUICK COMMAND has one byte. With no PEC, a QUICK COMMAND has zero bytes.
Note that the byte count does not increment as bytes arrive. No bits are set in the PMBST register until a stop message is received, the receive buffer is full, or a fault occurs. Then, all appropriate bit values are placed in the register together. All that is necessary to receive a quick command is to ACK the message by writing a one to the PMBACK register.