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dbgAutoCellFunction and RC scale factors

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 Dear All,

I have two questions regarding Encounter v6.2:

1) I read somewhere that before starting to work on a design in Encounter I should do: set dbgAutoCellFunction 1

Does anyone know why is that? What does this function do?

2) Does anyone know where to find or how to calculate the Capacitance/Resistance Scale Factors that are needed for RC extraction? These are filled in the Avanced> RC Extraction tab of Design Import window.

 Thanks in advance,

 Alex

Parents

  • Hi,

    The signoff extractor is not used throughout the flow (this would take too long). The extraction used until you switch to the signoff extractor is fast but not as accurate. That's why we use scaling factors. Sometimes the built-in extraction is too pessimistic, sometimes it's too optimistic.

    Once you generate scaling factors, they you typically go back to the beginning of the design and start again. This time the scaling factors will guide the timing optimization to be closer to signoff timing. However, you may have some other issues going on here. Density CANNOT be more than 100%. Your floorplan might be too small, or you might have timing targets that are too aggressive, causing lots of cells to get added.

    I would suggest using the full set of scaling factors, as in my last post. I would also suggest using MMMC to keep track of everything nicely, even if you don't have a lot of modes/corners.

     - Kari 

Reply

  • Hi,

    The signoff extractor is not used throughout the flow (this would take too long). The extraction used until you switch to the signoff extractor is fast but not as accurate. That's why we use scaling factors. Sometimes the built-in extraction is too pessimistic, sometimes it's too optimistic.

    Once you generate scaling factors, they you typically go back to the beginning of the design and start again. This time the scaling factors will guide the timing optimization to be closer to signoff timing. However, you may have some other issues going on here. Density CANNOT be more than 100%. Your floorplan might be too small, or you might have timing targets that are too aggressive, causing lots of cells to get added.

    I would suggest using the full set of scaling factors, as in my last post. I would also suggest using MMMC to keep track of everything nicely, even if you don't have a lot of modes/corners.

     - Kari 

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