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RMees's avatar
RMees
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7 years ago

SuperlightII word alignment fails on cable.

I have ported the SuperLightII example design on a Nallatech 385 board (ARIA 10 10AX115S2F45I2SGES).

The IP works fine if I use a loopback device on the QSFP port.

But when I connect two ports, each connected to a SuperlightII IP instance, the IP fails to link up most of the time.

I looked into the internal status and I can see that the word alignment is not achieved on 1 or 2 lanes.

On the few occasions that I get linkup, I am able to transfer 32MB of data without error.

I used the transceiver toolkit to check the link. The toolkit never detects any error.

Are there any changes I need to do to the IP for it to work on a cable instead of a loopback device?

3 Replies

  • Gigi's avatar
    Gigi
    Icon for New Contributor rankNew Contributor
    7 years ago

    Hi @RMees​

    Are you using optical or copper cables?

    Are you using hardware tested and recommended by Nallatech (now BittWare)?

    Thanks,

    G

  • RMees's avatar
    RMees
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    7 years ago

    At the moment I use a Cisco QSFP-40G-SR4 module, instead of the Finisar that Nallatech has used for testing.

    Finisar modules have been ordered and should arrive this week.

    I think that if the transceiver toolkit test doesnt detect any errors then the physical link is not causing the problem.

    As I understand it the word alignment is reached by the NIOS core adjusting the data capture.

  • Nathan_R_Intel's avatar
    Nathan_R_Intel
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    7 years ago
    It seems with the QSFP module, the signal is degraded that you cannot achieve word alignment. Suggest to try increasing your Transmitter Vod and Pre-emphasis Post Tap 1 value to check if you can get an error free transmission. Regards, Nathan