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TPSM8D6C24: Read PMbus registers

Itzik Zalma
Prodigy 70 points
Part Number: TPSM8D6C24

Tool/software:

Hi

I tried to read parameters from PMBUS and I succeed to read:

READ_IOUT (0x8C)

READ TEMPERATURE_1 (0x8D)

READ_VIN (0x88)

But when I tried to read READ_VOUT I didn't get any answer ( the chip not answer)

Do I need special configuration to read the READ_VOUT register?

Thanks

  • 0
    TI__Expert 6556 points

    Hello, 

    No special setting should be required to read vout. If you can provide pmbus transaction log that will help us investigate some possibilities

    Best regards,

    Britton

  • 0 in reply to Britton Jones
    Prodigy 70 points

    Hi

    Thanks for answer, some extra explanation 

    When we are reading IOUT (0x8C), Vin (0x88) or Temperature (0x8D) we are receiving valid values.

    When we try to read VOUT (0x8B) we receive the previous data. For example if we read Vin before VOUT, the results reading VOUT will be the last VIN reading.

    Attached a picture of VOUT transaction:
    Our ID is 0x28

    Opcode 0x8B

    What’s the difference between VOUT and the other 3 opcodes that we successfully read?

    Thanks,

  • 0 in reply to Itzik Zalma
    TI__Expert 6556 points

    Hi Itzik, 

    The only difference between READ_VOUT and the other telemetry commands is that VOUT's value is dependent on the formatting in VOUT_MODE; the absolute vs relative format, as well as the exponent parameter. 

    Are you familiar with our Fusion Power Designer GUI for PMBUS evaluation? We have a convenient transaction log that generates a text file of all of the PMBUS transactions sent/received from the device. This will likely help us debug further. I would like to see the returned transaction value for VOUT_MODE, then for READ_VOUT. Then testing a read of READ_VIN, followed by another read of READ_VOUT. I would like to see how this behaves

    Link to Fusion Digital Power Designer: https://www.ti.com/tool/FUSION_DIGITAL_POWER_DESIGNER

    After the device is detected you may use the top menu bar to turn on PMBUS logging and to open up the low level SAA / I2C /PMBUS tool and perform transactions in hex format. You can share the text log here after

    Best regards,

    Britton