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Ideal net in ETS

Jaydip Mehta
I have reset synchronizer at ip TOP whose output goes to reset/set pin of ALL the flop in my IP. I want to declare this net as an ideal net. How can I do this in ets? rtlcompiler by default considers all reset and clock nets as an ideal. But what about ets? Quite surprisingly, set_ideal_network is not supported in ets !

  • Hi Jaydip,

    following are something you can do. Not sure why set_ideal_network is not supported considering it is a broadly used feature and SDC 1.7 actually supports it as well. Hopefully, it will be supported soon. In the meantime, I believe set_ideal_net is supported as well as the native command setExcludeNet. You can try something as described below:

     

    1. specify the netname and the delay in a file in the following format

    netName netDelay

    example: n8 0ns

    2. Read the file into ETS using the following command.

    setExcludeNet -file exclude_nets.file

    3. Run report_timing.

    For the nets that are present in the excludeNet file, the delays in the file are considered and delay calculation will not compute the delays.

    NOTE:

    In the setExcludeNet file the transition and capacitance values may also need to be used. Otherwise the net driver cell still sees a huge load. Subsequently an unrealistically large delay will be seen on the driver cell.

    good luck,

    gh-

  • Hey grasshopper, Thanks for nice explanation. Its working fine. My exclude_nets.file looks like this : rst_n 0 0 0. I am keeping three zeros to have delay, capacitance and transition all three 0. I have one more question, why setexcldenet command explanation is not available in ANY ets document? Where can I find syntax for this command?

  •  Hi Jaydip,

     glad to hear workaround is working for you. I am just as puzzled as you WHY it is not documented. Hopefully ETS folks will document it soon. If it is of any value, I've seen it documented in the First Encounter docs

     

    gh-

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