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HOLD FIX FLOW IN ENCOUNTER

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Can anyone please explain the hold fix flow to be followed in encounter. I am trying to put a dontuse on many buffer cells but they are still being used when I use the FIXHOLD and optDesign -hold command.
Also it would help if yusers could commnent  on how good is encounter in fixing Hold. What are the techniwues used by encounter to fix hold. Does it use only delay insetion in the datapath or does much more to optimize hold violations


Originally posted in cdnusers.org by mvvijay78
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  • Hi Ed,

    That's a difficult question to answer. It's really just a feel you get after working in a certain process for a while. We had a customer that was doing their first 90nm design, and they were very paranoid about hold margin and picked a large number. We knew from doing many 90 nm designs that what he picked was unrealistic, and we were able to suggest something more reasonable. Some folks base it on a percentage of the clock period. Also, it's usually a combination of time to account for clock jitter, and some extra padding. But depending on whether you're using OCV or not, you can adjust the extra padding part. Also, you don't want to pick a hold uncertainty number that makes your design blow up (so many buffers get added that your utilization goes through the roof). Sorry I can't give a more concrete answer.

    - Kari


    Originally posted in cdnusers.org by Kari
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  • Hi Ed,

    That's a difficult question to answer. It's really just a feel you get after working in a certain process for a while. We had a customer that was doing their first 90nm design, and they were very paranoid about hold margin and picked a large number. We knew from doing many 90 nm designs that what he picked was unrealistic, and we were able to suggest something more reasonable. Some folks base it on a percentage of the clock period. Also, it's usually a combination of time to account for clock jitter, and some extra padding. But depending on whether you're using OCV or not, you can adjust the extra padding part. Also, you don't want to pick a hold uncertainty number that makes your design blow up (so many buffers get added that your utilization goes through the roof). Sorry I can't give a more concrete answer.

    - Kari


    Originally posted in cdnusers.org by Kari
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