SPRUJ53B April 2024 – September 2024 TMS320F28P550SJ , TMS320F28P559SJ-Q1
The Process Call (Figure 27-16) protocol consists of a Write Word message, followed by a Read Word message, without a stop condition between the two messages. A PEC byte can be appended to the read data from the target as an option to the message protocol. The PMBCCR register includes a PRC_CALL bit, which enables the transmission of a Process Call message onto the PMBus. The PMBus module automatically generates a repeated start condition and initiates the Read Word portion of the message when the process call bit is enabled.
To complete the Write Word portion of the Process Call, the PMBTXBUF register is loaded with the command byte in bits 7-0 and the data bytes are loaded into bits 23-8 of the register.
After programming the PMBCCR register, the PMBus module transmits the Process Call Message. The firmware can wait for an End of Message interrupt from the module to determine the validity of the message. Upon the receipt of the EOM, the PMBSTS register can indicate the receipt of 2 bytes from the Read Word portion of the Process Call message and the status of the target acknowledgment of the transmit data. If PEC processing is enabled, the PEC_VAL bit within the PMBSTS register indicates the accuracy of the PEC byte received from the target during the Read Word part of the message.
The PRC_CALL bit within the PMBCCR register must be disabled for the next non-Process Call message. Note that any write to the PMBCCR register initiates a message, so reconfiguration of the controller is not recommended until the firmware requires a new message to be transmitted.