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NuvKFC's avatar
NuvKFC
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3 years ago
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How to constraint min delay between LCELLs?

Some asynchronous need to use LCELLs to generate pulses, like following example.

However, the delay of LCELLs is different on the difference FPGA device.

So, I use following constraints to constraint the min delay of LCELL.

But it doesn't work.

How to constraint min delay between LCELLs?

Thank you very much.

Ex.:

lcell dly1d (.out(y1), .in(A) );

lcell dly4d (.out(y), .in(y1) );

Constraints:

set_min_delay 5.0 -from [get_pins dly1d|combout] \

-to [get_pins dly4d|combout]

set_net_delay -min 5.0 -from [get_pins dly1d|combout] \

-to [get_pins dly4d|combout]

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    • NuvKFC's avatar
      NuvKFC
      Icon for Contributor rankContributor
      3 years ago

      Hi Nurina
      Thank you, Nurina, very much.

      I had tried following constraint to limit the min delay between LCELLs to more than 0.8 ns.

      But it fail.

      After compiling done, I report the path delay in TimeQuest, which is from the LCELLs output to another LCELLs output.

      The delay time still small than 0.8 ns.

      Constraints:

      set_min_delay 0.8 -from [get_pins dly*d|combout] \

      -to [get_pins dly*d|data*]

      Report command:

      report path -from [get_pins dly*d|combout] -to [get_pins dly*d|combout]

      Design:

      lcell dly1d( .out(Y1), .in(A) );

      lcell dly2d( .out(Y2), .in(Y1) );

      lcell dly3d( .out(Y3), .in(Y2) );

      lcell dly4d( .out(Y4), .in(Y3) );

  • Nurina's avatar
    Nurina
    Icon for Regular Contributor rankRegular Contributor
    3 years ago

    Hello,


    Just like set_max/min_delay, set_net_delay requires the path to have a setup/hold relationship (reg to reg path). So it doesn't go through comb logic.


    Regards,

    Nurina


    • NuvKFC's avatar
      NuvKFC
      Icon for Contributor rankContributor
      3 years ago

      Hi Nurina
      Thank you, Nurina, very much.

      OK, I get it. Thank you very, very much.

  • Nurina's avatar
    Nurina
    Icon for Regular Contributor rankRegular Contributor
    3 years ago

    Hello,


    No problem! I’m glad that your question has been addressed, I now transition this thread to community support. If you have a new question, feel free to open a new thread to get the support from Intel experts. Otherwise, the community users will continue to help you on this thread. Thank you.

    Regards,

    Nurina


    P/S: If you like my comment, feel free to give Kudos. If my comment solved your problem, feel free to accept my comment as solution.


    • NuvKFC's avatar
      NuvKFC
      Icon for Contributor rankContributor
      3 years ago

      Hi Nurina
      Thank you, Nurina, very much.

      OK. No problem! Thank you very, very much.