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Help with PL Ethernet with SFP module in UltraZed

daniel.santamaria

Hello,

I am trying to use the SFP+ interface of the UltraZedEV card to echo IP traffic (with PL Ethernet).

In my design with Vivado, I use the "GTH-10GBASE-R" IP core.

I have a problem with the "GT reference clock", since in the AVNET card the GTH clocks that can be used DO NOT have a frequency that is valid for the IP core "GTH-10GBASE-R", according to the "UltraScale FPGAs Transceivers Wizard (1.7)" of Vivado.

That is, the AVNET card has the following GTH clocks: 148.5MHz (GTH_REFCLK[0] for HDMI and GTH_REFCLK[5] for Aux) and 250MHz (GTH_REFCLK[2]-SDI). In addition, external clocks to the Carrier could be used, but I have no possibility of having them. These external clocks would be from the SMA interface (GTH_REFCLK[3] and GTH_REFCLK[7]) and from the FMC (GTH_REFCLK[4] and GTH_REFCLK[6]). The GTH_REFCLK[1] would remain, which is from the HDMI_RX.

Of these previous clocks, you would only be able to use the 148.5MHz and 250MHz ones, which are not valid in the core IP "GTH-10GBASE-R", according to the "UltraScale FPGAs Transceivers Wizard (1.7)" of Vivado.

I need to find a reference clock that works for the core IP "GTH-10GBASE-R"...

Somebody could help me?

Can anyone think of any other possibility to use the SFP interface on the UltraZedEV card?

Thank you for helping!

  • Hi Daniel,  Could you use an additional Clocking Wizard IP to use the given clocks and re-generate one that is compatible with the 10GBase-R IP core?  Lookup PG065 for more info on the IP.

    Cheers!

  • in reply to lightcollector

    Hello!

    Thanks for answer so soon.

    Before I was trying to create the clock that was needed with an MMCM (with the Clocking Wizard IP), but in Vivado I got an error in the implementation.

    So I searched for more information about transceiver clocks and it seems that you can only use the clocks coming directly from the Transceivers pins (in my case they are called GTH_REFCLK, or something similar), in addition to having to instantiate the primitive IBUFDS_GTE4, necessary for its correct routing.

    Therefore, I understand that I can't use other clocks that don't come from those pins. Although it is true that I am not entirely sure, but from what I have seen I understand that it must be so.

    Thank you for helping!

  • in reply to daniel.santamaria

    Hi Daniel,

    When I read the part about the IP core only accepting valid clocks I thought it was for the logic rather than its direct connection to transceiver pins.  Sorry.

    Yes, the transceivers must specifically route clocks through its own conditioning and clock domains, that part you can't get around.

    If it is an issue of not having an external clock source there are GPSDOs that are not that expensive.  What I can't tell you though is would any specific model work reliably with the Ultrazed EV; I don't know if the quality of the clock or levels are fully compatible.  Search around, one that I have used for a different purpose came from Leo Bodnar in UK.

    Regarding the EV Carrier card, both clock gen chips are programmable and can output a range of frequencies.  Both parts are Renesas: https://www.renesas.com/us/en/document/dst/5p49v5935-datasheet and https://www.renesas.com/us/en/document/dst/8t49n241-datasheet?r=163511

    I haven't custom programmed either one, so can't advise you in that regard at this time.

    Cheers!

  • in reply to lightcollector

    Hello!

    Thanks for answering me!

    I think the two options that you propose are very interesting: external clock, and programming the frequencies of the "clocks gen chips".

    I will try the option to program the frequency of the "clock gen chip" used for the GTH (in PL side). I don't know how to do it, so I'll look for information.

    Thank you!