SPRUJ53B April 2024 – September 2024 TMS320F28P550SJ , TMS320F28P559SJ-Q1
The PMBus module provides support for extended commands that allow for an extra 256 command codes. Both command bytes are stored in the PMBRXBUF register along with the data bytes. In recognizing the extended command messages, the Repeated Start bit and the Rd Byte Count Bits within the PMBSTS register are utilized. For Extended Command Write Byte and Write Word messages (Figure 27-12), the two command bytes are stored in bits 15-0 of the PMBRXBUF register. The initial command byte must hold the command extension code, representing utilization of the extended command protocol. The Repeated Start bit is also set, received after the retransmission of the device address. The Rd Byte Count equals 3 for an Ext Cmd Write Byte message and 4 for an Ext Cmd Write Word message.
For the Extended Command Read Byte and Read Word messages (Figure 27-13), the module generates a data ready and data request interrupt following reception of the repeated device address. The two command bytes are found in bits 15-0 of the PMBRXBUF register, with the initial command byte matching the command extension code. The firmware is required to load transmit data to complete the message back to the controller.