Comments on: Controlling the power supplies on a Xilinx KC705 FPGA board with PMBus https://billauer.se/blog/2018/01/pmbus-vadj-fmc/ Anything I found worthy to write down. Thu, 26 Mar 2026 13:15:15 +0000 hourly 1 http://wordpress.org/?v=3.1.2 By: Dwight Larson https://billauer.se/blog/2018/01/pmbus-vadj-fmc/comment-page-1/#comment-1491 Dwight Larson Sun, 12 Apr 2020 15:02:16 +0000 https://billauer.se/blog/?p=5350#comment-1491 Here are a couple tips/corrections that might help... You got 0xFF results after an inadvertent STOP condition because no PMBus transaction may begin with a the "read bit" in the device address. If you don't do the repeated start, you really are starting fresh; there's no memory of the previous command code. Second - the LINEAR11 format is signed. Both the 5-bit exponent and the 11-bit mantissa are two's complement numbers. Here are a couple tips/corrections that might help…

You got 0xFF results after an inadvertent STOP condition because no PMBus transaction may begin with a the “read bit” in the device address. If you don’t do the repeated start, you really are starting fresh; there’s no memory of the previous command code.

Second – the LINEAR11 format is signed. Both the 5-bit exponent and the 11-bit mantissa are two’s complement numbers.

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