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DDC101: No data present on DOUT

Dan Krones
Prodigy 60 points

Part Number: DDC101
Other Parts Discussed in Thread: DDC112,

system clock is 2 mhz

I have loaded a setup word and am producing regular fds pulses

I see data valid going low and data transmit is going low prior to clocks

I am issuing 20 clocks and then turning off the data transmit signal

there is never any data on the data out line - always low

assistance is needed!

  • 0
    TI__Genius 11550 points

    Hi Dan,

    The DDC101 is currently not recommended for new designs. We recommend DDC112 as an alternative device for your design. 

    Thanks.

    -TC

  • 0 in reply to TCT
    Prodigy 60 points

    I am aware of this fact however our system already has a DDC101 installed in it and I need to get this part working.  Can you assist?

  • 0 in reply to Dan Krones
    TI__Genius 11550 points

    Hi Dan,

    It is difficult to say exactly what the issue is with the given information. In order to help us understand better and to debug the issue, please let us know some details. 

    1. Is the system with the DDC101 design working previously? 

    2. Are you seeing this issue on some system or only on a specific system?

    3. Does this happen with different devices or they all behave the same?

    4. It will be helpful if you can provide some scope shots of your signals.

    Thanks

    -TC

  • 0 in reply to TCT
    Prodigy 60 points

    This is a new design.  I have only tested 2 systems so far and they both perform the same way.

    It seems the image I embedded did not stay embedded.  This edit attaches a screen shot.

    DOUT tri-states until it is enabled by pulling the data transmit in low (TX channel 4).  DOUT was always just low and we were trying to diagnose if it was even being enabled at all.  I tacked a 10k pullup resistor on the DOUT line which is why this screen shot shows DOUT as high until the DDC pulls it low when Data Transmit In is enabled.

  • 0 in reply to Dan Krones
    TI__Genius 11550 points

    Hi Dan,

    Thanks for the scope plot. This is a really old device that has limited support. I'll check with the team and get back to you.  

    Thanks.

    -TC

  • 0 in reply to TCT
    Prodigy 60 points

    I just figured out what was wrong.  The Read Data/Setup In pin was being held low which disabled the output.  As soon as I de-asserted that pin I got data on DOUT.

    Thanks for the assistance!

    -Dan

  • 0 in reply to Dan Krones
    TI__Genius 11550 points

    Hi Dan,

    Thanks for the update. It is good to hear you got the device working in your system. . 

    Thanks.

    -TC