SPRUJ53B April 2024 – September 2024 TMS320F28P550SJ , TMS320F28P559SJ-Q1
A Send Byte message (Figure 4-3) consists of the device address, a single data byte, and an optional PEC byte. To process the PEC byte correctly, PEC processing must be enabled in the PMBTCR register. In automatic address acknowledge mode, the data and optional PEC byte are acknowledged without firmware interaction. The module generates an End of Message interrupt, reads the status register and finds the data ready indication bit set. In manual mode, the address is acknowledged by the firmware, while the remaining data and PEC bytes are acknowledged by the module.
The PMBus module stores Data Byte #0 into the PMBRXBUF register. The data byte is stored into bits 7-0. In non-PEC mode, the RX Byte Count in the PMBSTS register indicates one byte received. If PEC processing is enabled, the PEC byte is also stored into the PMBRXBUF register, with the PEC byte residing in bits 15-8. The RX Byte Count in the PMBSTS register indicates two bytes received. The PEC Valid bit in the PMBSTS register indicates the validity of the received PEC byte.
When a Send Byte message is received, the Data Ready bit is set along with the EOM and, assuming that the PEC is valid, the PEC valid bit. The read byte count (RD_BYTE_COUNT) register contains a 2. All that is necessary to receive a send byte command is to ACK the message by writing a 1 to the PMBACK register. Before doing the ACK, read the byte from the lowest byte of the PMBRXBUF register.