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DNguy4's avatar
DNguy4
Icon for Occasional Contributor rankOccasional Contributor
7 years ago

How Quartus route clock after pll?

Hi,

If i have the same clock going to two registers, Quartus will ensure that the clock arrives at these two registers at the same time for synchronous design.

If I have two clocks with the same frequency from two output pins of a pll going to two registers, will Quartus ensure that these two clock arrive at the same time? or it will treat them as two independent clocks? I think it will treat them as two independent clocks but just want to double check.

Thanks

3 Replies

  • DNguy4's avatar
    DNguy4
    Icon for Occasional Contributor rankOccasional Contributor
    7 years ago

    Thank you JwChin. To synch those clocks, the only option is the max/min skew in the constrain, right?

  • JonWay_C_Intel's avatar
    JonWay_C_Intel
    Icon for Frequent Contributor rankFrequent Contributor
    7 years ago

    Hi @DNguy4​ , if you have 2 independent clock, most probably PLL will route them to 2 different GCLKs. The skew between each GCLK is minimum. If you would like to constrain, you can constrain them to different GCLK and see which GCLK combination has the lowest skew.