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open01's avatar
open01
Icon for Occasional Contributor rankOccasional Contributor
4 years ago
Solved

Timing Analyzer

Hi,

I have two questions about Timing Analyzer.

1. As show in the fig, Quartus reminds me that I have two Unconstrained Clocks, But these two are not clock signals in my design, how can I correct them?

2.If I have a hold violation in my project, as shown in the figure, how can I fix it?
Can I fix it by adding a delay cell? How can I add a delay cell to my data path?

I appreciate your help very much.

O.Chiang

  • open01's avatar
    open01
    4 years ago

    Hi,
    I know where the problem is.

    Because my design accidentally synthesized a latch, and these two signals are connected to latch_en, Quartus regards these two signals as clock.
    When I removed the latch, the situation was resolved.

    Thank you very much for your help.

    O.Chiang

3 Replies

  • sstrell's avatar
    sstrell
    Icon for Super Contributor rankSuper Contributor
    4 years ago

    You don't mention what clocks the tool is telling you are unconstrained. What are they? If it's the JTAG clock, look at this:

    https://www.intel.com/content/altera-www/global/en_us/index/support/support-resources/knowledge-base/solutions/rd04282008_867.html

    As for the hold timing issue, without seeing the design or the .sdc (or even knowing what path is failing timing), this isn't really possible to solve. It looks like you're going between two different clock domains and maybe need multicycle, but it's impossible to tell for sure.

    • open01's avatar
      open01
      Icon for Occasional Contributor rankOccasional Contributor
      4 years ago

      Hi, thanks for your reply

      About the first question. I mean, Quartus mistaken the signal for a clock signal, in fact he told me that the two Unconstrained signals are not a clock signal in my design. Those two signals are just normal Register output's data.

      Regarding the second question. I found my mistake after your hint, maybe I only need to set the path to false path, thank you very much!

      I appreciate your help very much.

      O.Chiang

    • open01's avatar
      open01
      Icon for Occasional Contributor rankOccasional Contributor
      4 years ago

      Hi,
      I know where the problem is.

      Because my design accidentally synthesized a latch, and these two signals are connected to latch_en, Quartus regards these two signals as clock.
      When I removed the latch, the situation was resolved.

      Thank you very much for your help.

      O.Chiang