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DONT USE cells & uncertainties

sureshm

 Hi All, 

 This may a pretty  easy questions for most of the community in here. Can you please let me know the methodology of arriving @ the 

DONT use list from the given technology library @ various levels of the implementation flow ..( synth, CTS,PnR, ECOs) ? 

Also, I am not clear on the Uncertainty numbers being used for a design ?  What are all the things to keep in mind for te calculation of Uncertainties? Is it some blanket % use for the uncertainity or any connection with the Foundary details, and some analysis on the OCV numbers , Jiitter and so on.. ?  

Thanks in advance 

suresh 

Parents
  • Hi Suresh,

      There are a number of consideration used to determine which cells to avoid from a given library for a wide variety of reasons; electro-migration, delay, congestion, drive strength... unfortunately there is no simple answer to such a question and would require detailed understanding of the design intent and application.

      For the uncertainty yes it is use for a number of reasons including, cycle to cycle jitter, clock skew before clocktree insertion and margin for downstream effects like xtalk & detour routing. OCV while a real effect uses a different mechanism set_timing_derate command which is more appropriate for the condition.

    Cheers,  Mike
Reply
  • Hi Suresh,

      There are a number of consideration used to determine which cells to avoid from a given library for a wide variety of reasons; electro-migration, delay, congestion, drive strength... unfortunately there is no simple answer to such a question and would require detailed understanding of the design intent and application.

      For the uncertainty yes it is use for a number of reasons including, cycle to cycle jitter, clock skew before clocktree insertion and margin for downstream effects like xtalk & detour routing. OCV while a real effect uses a different mechanism set_timing_derate command which is more appropriate for the condition.

    Cheers,  Mike
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