SNIU028D February 2016 – September 2020 UCD3138 , UCD3138064 , UCD3138064A , UCD3138128 , UCD3138A , UCD3138A64
The PMBus Interface must support the Group Command Protocol. The Group Command Protocol is used to send commands to more than one device within the same message. When devices on the PMBus detect the stop condition at the conclusion of the Group Command message, the received commands are executed concurrently. To initiate a Group Command, the GRP_CMD bit within the Master Control Register must be set when programming the slave address for the first device in the message. The rest of the message is processed as a write byte/word message. At the conclusion of the first part of the Group Command message, the firmware programs the next device address in the Master Control Register. The PMBus Interface will initiate a repeated start on the bus and start the next part of the message. When programming the last device address of the Group Command message, the firmware must disable the GRP CMD bit when programming the Master Control Register.