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DS90UB925/6 BIST Question

will oneill
Prodigy 100 points

Hello,

I want to make use of the Built-In Self Test feature of the the DS90UB925/6. I have a two boards connected like this, [Board 1] <-> [Serialiser] <--> [Deserialiser] <-> [Peripheral board].

I'm planning on disabling/enabling BIST on the deserialiser via the I2C interface, although I find that as soon as I enable it, I lose the I2C link between the serialiser/deserialiser, meaning I can't disable it. 
Is controlling BIST via I2C not supported in this configuration or should this work?

Thanks,

Will.

  • 0
    TI__Genius 13475 points

    Will - this should work.

    Have you tried enabling/disabling BIST by use of the BIST pin on the deserializer?, and confirmed that this works?

    Assuming that the pin mode BIST works, can you confirm that the I2C link is working by writing to, and then reading back from the registers in the deserializer from the serializer.

     

  • 0 in reply to Mark Sauerwald88474
    Prodigy 100 points

    Hello,

    I only have access to the deserialiser using the I2C interface via the serialiser.  I can read the registers initially like this:

    [   19.347329] Reg 0: 58h
    [   19.455194] Reg 1: 04h
    [   19.558662] Reg 2: 00h
    [   19.662198] Reg 3: F0h
    [   19.765680] Reg 4: FEh
    [   19.869181] Reg 5: 1Eh
    [   19.972685] Reg 6: 00h
    [   20.076193] Reg 7: 18h
    [   20.180190] Reg 8: 00h
    [   20.283670] Reg 9: 00h

    Then after writing 01h (BIST Enable) to register 24h (BIST Control), the I2C read calls time out.

    I've also tried writing 07h or 03h to BIST Control to use different clock sources, and it does the same thing.

  • 0 in reply to will oneill
    Prodigy 100 points

    Hi,

    Any idea about this one? If I don't have access to the pins, and only have access via the I2C interface from the serialiser, does the I2C interface work after the BIST is enabled?  If it doesn't we need to look into an alternate method of testing the interface.

    Thanks,

    Will.

  • 0 in reply to will oneill
    TI__Genius 13475 points

    Will

    The I2C backchannel should continue to work during BIST operation.

    Mark

     

  • 0 in reply to Mark Sauerwald88474
    Prodigy 100 points

    Ah okay, do you know what would cause the interface to stop working, or if there is some configuration setting I should be using while making use of BIST to maintain the I2C connection?

    Thanks,
    Will.

  • 0 in reply to will oneill
    Prodigy 100 points

    Hi, I'm still having trouble with this.  The datasheet for the serialiser says this regarding the I2C interface:

    The bidirectional control channel is implemented via embedded signaling in the high-speed forward channel (serializer to deserializer)
    as well as lower speed signaling in the reverse channel (deserializer to serializer).

    doesn't this imply that when the BIST is enabled, and the HS_FC is used for the test, I2C comms will only work from deserialiser to serialiser.?

  • 0 in reply to will oneill
    TI__Intellectual 2515 points
    Hi Team,

    Please allow me to get into this communication.
    Because I had same trouble, tried to post question,
    and found this topic on E2E forum.

    I tried to access registers in DS90UB926 (De-serialize) through DS90UB925 (Serializer)
    It works good in normal operation mode.
    However, when I switched to BIST mode, either PIN mode or register mode, I cannot access
    Register in remote device (DS90UB926 De-serializer).

    I suspect that in BIST mode, low speed data seemed to be blocked.
    Can you check with EVK and/or designer, if this behavior is as designed or not?

    Mita
  • 0 in reply to Kikuo Mita
    TI__Intellectual 1820 points

    Mita-san,

    The I2C pass-through feature is not available when in BIST mode. Both the forward channel and the backchannel are sending randomized patterns when BIST mode is activated. For this reason, BIST must be controlled locally at the deserializer side (either by pin or through register).

    Best Regards,

  • 0 in reply to Naomi Sugiura42
    TI__Intellectual 2515 points

    Sugiura-san,

    Thank you for the answer.

    Mita