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DP83TG720EVM-MC: Difference between roles (Master and slave)

Connor Danes
Prodigy 30 points
Part Number: DP83TG720EVM-MC


Tool/software:

Hi all, 

Whilst experimenting with adding series termination to the ethernet cable between the two dev kits, we have noticed that there seems to be a difference in error counts for either devkit when set in a different role (master/slave). The master seems to have a lower error count rate and higher signal quality index, regardless of the kit used.

Do you know why this might be?

  • 0
    TI__Genius 11930 points

    Hi Connor,

    The SQI typically would not be different between roles, it is an indication of the overall link quality.  There could be some slight difference in the connector (Routing) or cable and orientation. Do you see values that are different by more than one index(I would expect some variation which would be 1-2dB)?

  • 0 in reply to Undrea Fields
    Prodigy 30 points

    Hi Undrea,

    I am seeing this regardless of which of my development kits are in the master role, and regardless of the orientation of the cable. Here are some results which are indicative of what I am seeing:

    The load is a series termination on the wires.

    As you can see, all the counts are much different between the roles

    This was produced by connecting a cable between two PHY dev kits, assigning roles and then counting changes in the registers over 10s. (No test mode enabled)

  • 0 in reply to Connor Danes
    TI__Mastermind 37323 points

    Hi Connor,

    Can you share more details on where are you adding the series termination resistor?  Also, can you share some background for this testing?

    Thanks,

    Drew

  • 0 in reply to Drew Miller1
    Prodigy 30 points

    Hi Drew, the series resistance is soldered onto the cable, about a quarter of the way along a 10m cable, closer to the master. This is also the same if the cable is flipped, or if the dev kits have swapped roles. The background is largely us trying to get a gauge of how the error counts change with decreasing signal quality, to get a grip of how we can use these numbers