SPRUI33H November 2015 – June 2024 TMS320F280040-Q1 , TMS320F280040C-Q1 , TMS320F280041 , TMS320F280041-Q1 , TMS320F280041C , TMS320F280041C-Q1 , TMS320F280045 , TMS320F280048-Q1 , TMS320F280048C-Q1 , TMS320F280049 , TMS320F280049-Q1 , TMS320F280049C , TMS320F280049C-Q1
The Process Call (Figure 25-16) 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 slave as an option to the message protocol. The PMBMC 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 PMBMC 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 slave 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 slave during the Read Word part of the message.
The PRC_CALL bit within the PMBMC register must be disabled for the next non-Process Call message. Note that any write to the PMBMC register initiates a message, so reconfiguration of the master is not recommended until the firmware requires a new message to be transmitted.