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HBhat2's avatar
HBhat2
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6 years ago

Experiment with S-10 Transceiver IO Terminations

Hi, I am performing some experiment with S-10 SoC Dev kit (L-tile). I am using FMC loopback cards to check the behavior of SERDES so as to use for my final requirement. My goal is to connect a dev...
CheepinC_altera's avatar
CheepinC_altera
Icon for Regular Contributor rankRegular Contributor
6 years ago

Hi HPB,

As I understand it, you seems to observe high BER when you are using TX output impedance 85 Ohm which is mismatching with the board trace of 100 Ohm. For your information, since there are impedance mismatch, I believe the high BER is due to the signal integrity issue. Generally it is recommended to use matching impedance.

You may try to run auto-sweep in TTK with different PMA analog settings to see if any of the combination can help for the failing case.

Please let me know if there is any concern. Thank you.

Best regards,

Chee Pin

  • HBhat2's avatar
    HBhat2
    Icon for Contributor rankContributor
    6 years ago

    Hi Chee Pin,

    <As I understand it, you seems to observe high BER when you are using TX output impedance 85 Ohm which is mismatching with the board trace of 100 Ohm.>

    Yes, you are right.

    Regarding Auto sweep, I did perform it and unable to get any best result with acceptable BER for failing cases. (Auto sweep for entire range of 0 to 31, with negative to positive boundary of pre-emphasis taps).

    Here, when I constraint only RX to 85-Ohm, then there is a good eye opening. In both the failing cases, TX is constrained to 85-ohm.

    So, I want to know, whether any Tx side configuration is there apart from VOD, pre-emphasis settings which I need to take care to transmit the signals with good integrity.

    With Regards,

    HPB