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DS90UB954-Q1: Question on Margin Analysis Program

Mitchell
Expert 4915 points
Part Number: DS90UB954-Q1

Hi Team,

My customer and I are currently looking over the new Margin Analysis Program and a question has come up on the flow chart (Figure 5) in the SNLA301 document.

How long does the AEQ dwell on each setting before moving on to the "AEQ Stop" position in the flowchart? Is this strictly a time delay, or perhaps is there some condition where a certain number of errors must occur. Or could it be a combination of both? Any clarity on how this logic works would be helpful.

The primary challenge we are facing right now is to just get a reliable link up and running. In your experience do you see most folks reverting to manual settings in order to get a reliable link? I was thinking the MAP tool should be able to automatically determine these settings. 

Thanks,
Mitchell

  • 0
    TI__Expert 3055 points
    Hi Mitchell,

    The EQ setting will be incremented if any errors/loss of lock is detected. The AEQ Stop is actually more like an AEQ Pause. If any errors or loss of lock is detected in the future, the EQ setting will be incremented again.

    If you are having trouble getting a reliable link, this typically is an indication of improper layout or cable issues. The purpose of the margin analysis tool is to help indicate the presence of these issues. There are guidelines both in the SNLA301 app note and the SNLU243 MAP user guide.

    Take a look at your results compared to the guidelines and see if that suggests some issues. If you share you results and conclusions along with the cable type, length, and # of interconnects, I can provide some additional guidance on whether the results seen are expected or acceptable.

    Regards,
    Zoe
  • 0 in reply to Zoe Nuyens
    TI__Expert 4915 points
    Hi Zoe,

    Thanks for the clarification on how the AEQ Stop timing works.

    I do have one more question on how the AEQ selects it's values. Basically, we are having trouble understanding what the 4x2 box & 4x1x3 recommendation have to do with the settings chosen by the AEQ. Can you explain further how these two are related?

    It seems that you’d want to land in the center of this region (or more specifically, at some point as far from any bad setting as possible) since it’s going to have the lowest BER. But instead, the AEQ always selects settings on the edge and seems to do so by design. By simply picking the first setting that has no errors observed within a certain brief period of time, we know two things: we have a reasonably high confidence that it has better than some atrociously high BER, and that it is adjacent to a setting that is worse.

    Thanks,
    Mitchell
  • 0 in reply to Mitchell
    TI__Expert 3055 points
    Hi Mitchell,

    Given that you have provided additional information by email, let's continue support for this offline.

    Regards,
    Zoe