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DP83826I: Is a permanent register value change possible?

Walter Ahrend
Intellectual 1350 points
Part Number: DP83826I

Tool/software:

My customer currently has 2 new prototpyes., each equipped with 2 DP83826I channels.

Because of ETH-compliance test issues he wrote new values to extended registers 0x30b and 0x30c in order to increase the output voltage swing for a specific test case.

Now one of the two prototypes does NOT return back to the default values after power-cycle, (it even has been switched off over night!) The next morning it still reads back the altered values from these registers!

The customer even re-flashed the complete prototype with a Test-Firmware that does not access any PHY on the boards but still can read back only the altered values...

Up to my knowledge this device is purely register-controlled, which is a NVM-technology and should return back to initial status after a power cycle...

Is there any other explanation possible besides a defective device? 

  • 0
    TI__Mastermind 19621 points

    Hi Walter,

    I agree that this is strange behavior.

    Questions:

    1. What are the original values vs altered values that you are writing?
    2. If you write to it again, will it stick to that new value?
    3. When power cycled, does the MDI output voltage still match the altered value?

    Regards,

    Alvaro

  • 0 in reply to Alvaro (Al-vuh-roe) Reyes
    TI__Intellectual 1350 points

    Hi Alvaro,

    here the answers to your questions:

    1. Original values are reset values i.e. VOD_CFG1 = 0x3C00, VOD_CFG2 = 0x0410, altered values are 0x3C40 and 0x13CF, respectively.
    2. Yes, the new value/s will stick, but only until the next power-cycle
    3. No, after power cycle the output voltage is the same as with reset values

    Alvaro, your questions imply that there is a possibility that our can permanently store some altered values... So is my assumption wrong that our PHY's are purely register-based with no means of permanent storage?

  • 0 in reply to Walter Ahrend
    TI__Mastermind 19621 points

    Hi Walter,

    Thank you for answering my questions. To answer yours, no our PHY does not have permanent storage.

    Walter Ahrend said:
    Yes, the new value/s will stick, but only until the next power-cycle

    "but only until the next power-cycle" what does that mean? VOD_CFG1 is set to 0x3C40, then written to another value (0x2C40 for example). If the board is power cycled, what does VOD_CFG1 read? It should be the default value of 0x3C00.

    Regards,

    Alvaro