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Bob, How can I constrain optDesign -hold to add buffers on end points only?

eminemshow

Bob,

Things are like this, I am now at the final stage of timing closure, since functional timing is clean and test timing is ongoing. There is not enough time to config a MMMC environment. After investigation, I found that if I can add all the hold buffers at SI pin of DFF at scan shift mode, then functional timing would be un-touched (as you know, at Q pin of DFF, things would be dangerous......). So I want to ask whether I can control optDesign to make end-point only buffer insertion when fixing hold.

Thanks.

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  • BobD

    For the optDesign -hold issue, I believe our hold fixing algorithm tends to insert buffers at endpoints, but I'm not aware of an option that would force this exclusively but I'll check.

    I was thinking of suggesting a script that dont_touched all nets other than those connected to SI pins on sequentials but I don't think that would guarantee the insertion occur only on SI pins (since the dont_touching would be done on a net basis and the net could connect to things other than SI pins).

    I don't think an MMMC configuration is required to get hold fixing to be setup-aware.  That is to say- even with min/max specified via a .conf file the tool should have the information it needs to do setup-aware hold fixing.

    -Bob

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  • BobD

    For the optDesign -hold issue, I believe our hold fixing algorithm tends to insert buffers at endpoints, but I'm not aware of an option that would force this exclusively but I'll check.

    I was thinking of suggesting a script that dont_touched all nets other than those connected to SI pins on sequentials but I don't think that would guarantee the insertion occur only on SI pins (since the dont_touching would be done on a net basis and the net could connect to things other than SI pins).

    I don't think an MMMC configuration is required to get hold fixing to be setup-aware.  That is to say- even with min/max specified via a .conf file the tool should have the information it needs to do setup-aware hold fixing.

    -Bob

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