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HBhat2's avatar
HBhat2
Icon for Contributor rankContributor
5 years ago

Native PHY Reference clock with SSC enabled

Hi, I am aware that Arria 10 native PHY does not support SSC (spread spectrum clocking) for any custom protocols. I am targeting to implement a custom protocol which needs SSC in the transceiver ...
CheepinC_altera's avatar
CheepinC_altera
Icon for Regular Contributor rankRegular Contributor
5 years ago

Hi HPB,

As I understand it, you would like to feed refclk with SSC for the A10 TX. You are not concern about the ppm violation at the A10 RX side. For your information, if you can ensure that the SSC is within the datasheet spec of "Spread-spectrum modulating clock frequency" and "Spread-spectrum downspread" for PCIe mode, there should be no issue with the TX and ATX PLL. I observe your specs seems to be within the specs. Note that you should perform thorough validation to ensure the functionality is meeting your expectation since using SSC for non-PCIe mode is something not validated and not a normal supported feature.

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

Best regards,

Chee Pin

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

    Hi,

    That means I can connect SSC enabled clock to Transceiver reference clock, but the clock's frequency variation must be within +/-300ppm wrt specified frequency.

    (for example, 156.25MHz +/- 300ppm, this varied ppm can be due to SSC down-spreading )

    With regards,

    HPB