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RE: SDF generation problem

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Hello Kari,

I’m trying to generate an SDF file in Encounter for backannotation, using the Timing>Calculate Delay command. My problem is that the resulting SDF file has the same value for min, typ and max delays, for example:

(INTERCONNECT I1/I0/I16/Z I1/I0/I14/A1 (0.0003:0.0003:0.0003) (0.0003:0.0003:0.0003))

Or

(CELL

  (CELLTYPE "CKND2D2")

  (INSTANCE I1/I7/I18)

  (DELAY

    (ABSOLUTE

      (IOPATH A1 ZN (0.0247:0.0247:0.0247) (0.034:0.034:0.034))

      (IOPATH A2 ZN (0.0382:0.0382:0.0382) (0.0464:0.0464:0.0464))

    )

  )

)

This is true for both SignalStorm and Encounter’s Delay Calculator. I tried to change the PVT conditions with setOpCond BCCOM | WCCOM | NCCOM but I’m getting the same numbers.

Please assist me with this. Thank you in advance.

 
Best regards,

Alex

IC Design Engineer
Parents

  •  Hi Alex,

    I believe the only way to have 3 corners loaded (min, typ, max) is to use MMMC. The "Common Timing Library" field in the .conf file is used when you are only loading one corner. So since you already provided min and max libs in the min lib and max lib fields, the common field was ignored.

    As for the differences, make sure you have the same setup in both cases. Check your setDelayCalMode, options to delayCal (the text command equivalent of Timing->Calculate Delay), and options to write_sdf. The write_sdf command is the recommended one when using MMMC, so if you go forward and set up MMMC, definitely use write_sdf.

    - Kari

Reply

  •  Hi Alex,

    I believe the only way to have 3 corners loaded (min, typ, max) is to use MMMC. The "Common Timing Library" field in the .conf file is used when you are only loading one corner. So since you already provided min and max libs in the min lib and max lib fields, the common field was ignored.

    As for the differences, make sure you have the same setup in both cases. Check your setDelayCalMode, options to delayCal (the text command equivalent of Timing->Calculate Delay), and options to write_sdf. The write_sdf command is the recommended one when using MMMC, so if you go forward and set up MMMC, definitely use write_sdf.

    - Kari

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