SNIU028D February 2016 – September 2020 UCD3138 , UCD3138064 , UCD3138064A , UCD3138128 , UCD3138A , UCD3138A64
The Write 4 Bytes message writes a 32 bit word into a specified address. The Write 4 Bytes message utilizes the PMBus write block message format. The PMBus Master initiates the message by sending the device address, a command byte of 0xF5, a block length of 0x8, the 32-bit write address location, four data bytes and a PEC byte. The Boot ROM interprets the command byte and stores the word at the write address specified by the incoming message.
Start | Device Address & R/W (0x16) | Command Byte (0xF5) | Block Size (0x08) | Write Address[31:24] |
Write Address[24:16] | Write Address[15:8] | Write Address[7:0] | Data[31:24] |
Data[23:16] | Data[15:8] | Data[7:0] | PEC | Stop |
The Write 4 Bytes message is normally very quick, and no PMBus delay is required. However, the Write 4 Bytes message can be used for writing to data and program flash, simply by writing to the appropriate address. In this case, 50 µsec should be allowed before starting the next message.