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TMDS181: Eye Scan without DDC

F.N
Expert 8760 points
Part Number: TMDS181

Hi team,

My customer is going to use TMDS181 as signal source distributor etc.
And the customer wants to use TMDS181 Eye Scan function.

So, the customer evaluated TMDS181RGZEVM Eye Scan fuction with Eye Scan tool.
The customer got eye diagram when DDC was input to TMDS181RGZEVM,
but couldn't get it when DDC wasn't input to TMDS181RGZEVM.

The customer has following two questions.

(1) Can we get eye diagram from TMDS181 when DDC isn't input to TMDS181?

(2) If we can get it from TMDS181 without DDC, is it due to Eye Scan tool
    that it can not be done with TMDS181RGZEVM without DDC?

Please let me know the answers.

Best regards,
Fumio Nakano

  • 0
    TI__Mastermind 23815 points

    Hi Fumio,

    TMDS181 only monitor DDC for changes in TMDS_CLK_RATIO, you can even write this bit by local I2C.

    Could you confirm when there is no DDC you have access to I2C registers?

    EyeScan tool only tak eye diagrams when TMDS181 is in retimer mode if the source and sink has no DDC, the source will send a default resolution that may be to small to set TMDS181 in retimer mode.

    When there is no DDC please check in EyeScan tool if the PLL is locked.

    Regards

  • 0 in reply to Moises Garcia
    TI__Expert 8760 points

    Hi Moises-san,

    Thank you for your prompt reply.

    The customer confirmed in EyeScan tool that the PLL was unlock when there was no DDC.

    The customer can access to I2C registers, so I requested the customer to read all
    the registers when there is no DDC.

    Best regards,
    Fumio Nakano

  • 0 in reply to F.N
    TI__Expert 8760 points

    Hi Moises-san,

    I heard that the customer resolved it.
    It is caused by a malfunction of the signal generator.

    By using normal signal generator, the customer could get eye diagram
    when DDC was not input to TMDS181RGZEVM

    Thank you for your support!!

    Best regards,
    Fumio Nakano

  • 0 in reply to F.N
    TI__Mastermind 23815 points
    Hi Fumio-san,

    Great news the application is working now!
    Remember TMDS181 monitors DDC for TMDS_CLK_RATIO, this is important when switching to data rates above 3.4Gbps. They will have to control this bit manually.

    Regards
  • 0 in reply to Moises Garcia
    TI__Expert 8760 points

    Hi Moises-san,

    Thank you for your advice.

    Best regards,
    Fumio Nakano