The MPM3695-10 datasheet isn’t clear about the size of the READ_TEMPERATURE_1 PMBus command. Is it 8-bit plus sign or 9-bit plus sign?
The command description indicates 8-bit plus sign and a range of -255 to +255.
READ_TEMPERATURE_1 (8Dh)
The READ_TEMPERATURE_1 command returns the internal sensed temperature. This value is also
used internally for over-temperature fault and warning detection. This data has a range between
-255°C and +255°C.
READ_TEMPERATURE_1 is a 2-byte, twos complement integer. The sign bit is bit[9]. Table 5 shows
the relationship between direct and real-world values.
But then it refers to Table 5 which shows 9-bits plus sign and a range of -511 to +511.
Table 5: Direct and Real-World Values for READ_TEMPERATURE_1
Welcome to the forum! Apparently the table was generated with Excel and it defaults to 9 bits plus sign so +511 to -511. But the MPM3695-10 and other versions use just 8 bits plus sign so are valid only for -255 to +255. Realistically its a formality since the device likely wont operate well at over +150’C or below -50’C.
Thanks for the clarification James. I don’t know if you are making an update to the datasheet, but if I understand correctly it should say:
READ_TEMPERATURE_1 (8Dh)
The READ_TEMPERATURE_1 command returns the internal sensed temperature. This value is also
used internally for over-temperature fault and warning detection. This data has a range between
-255°C and +254°C.
READ_TEMPERATURE_1 is a 2-byte, twos complement integer. The sign bit is bit[8]. Table 5 shows
the relationship between direct and real-world values.
With the bitfield table having “Sign” in the column for Bit 8 (the ninth bit).