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Lakshman-Athukorala's avatar
Lakshman-Athukorala
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4 months ago
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Cyclone 10 SERDES Receiver Timing Constraints

Hello, I am trying to send some data serially over a very simple SERDES interface made of a single LVDS clock and data going from FPGA 1 to FPGA 2. In the receiver FPGA (FPGA 2), I want to u...
  • ShengN_altera's avatar
    4 months ago

    Hi,


    Sorry for delay reply,


    Check this https://www.intel.com/content/www/us/en/docs/programmable/683520/22-1-20-0-1/timing.html:

    Use the Intel® Quartus® Prime software from version 14.0.a10 onwards to generate the required timing constraint to perform proper timing analysis of the LVDS SERDES IP core in Intel® Arria® 10 and Intel® Cyclone® 10 GX devices.


    And this https://www.intel.com/content/www/us/en/docs/programmable/683520/22-1-20-0-1/i-o-timing-analysis.html:

    In non-DPA mode, use RSKM, TCCS, and sampling window (SW) specifications for high-speed source-synchronous differential signals in the receiver data path. If there is additional board channel-to-channel skew, consider the total receiver channel-to-channel skew (RCCS) instead of TCCS where .


    Now you just need to set the RCCS, then it'll be auto implemented into auto-generated .sdc.

    RCCS = (Clock trace delay) - (Data trace delay) + margin

    Skew(ps) = (Trace length different in mm) * (propagation delay per mm, typically 5ps/mm for FR4)

    For example if your pcb analysis shows that the clock trace is 2mm longer than the data trace:

    Skew = 2mm * 5ps/mm = 10ps

    Add margin = (e.g. 20ps) = 30ps

    Set RCCS to 30ps


    Thanks,

    Regards,

    Sheng