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signoff timing analysis in MMMC mode

diablo

Hi, 

I am trying to do MMMC signoff timing analysis in encounter. The first method I tried was to just use timeDesign -signoff. However, when defining  create_rc_corner in MMMC mode, we need to provide -qx_tech_file qrc.tch -qx_conf_file qrc.config for encounter to run qrc extraction. I am not sure about the format and the content of this qrc.config file ? I would appreciate if anyone could provide some sample qx_conf_file.

The second method I am trying is generating  .SPEF file by running standalone QRC extraction for the design. Then use the following flow in encounter:

setAnalysisMode -analysisType onChipVariation -asyncChecks async -caseAnalysis true -clockGatingCheck true -clockPropagation sdcControl -cppr both -propSlew true -timingSelfLoopsNoSkew true -skew true

set_analysis_view -setup worst -hold best 


spefIn -rc_corner rc_worst $spef_dir/foo_qrc.spef_worst.spef
spefIn -rc_corner rc_best $spef_dir/foo_qrc.spef_best.spef


 timeDesign -signoff -reportOnly -pathReports -drvReports -slackReports -numPaths 50 -prefix wstbst -outDir SIGNOFF_TIMING/wst_bst/   
 timeDesign -signoff -reportOnly -hold -pathReports -slackReports -numPaths 50 -prefix wstbst -outDir SIGNOFF_TIMING/wst_bst/  

 Is this the correct flow? Do I still need to do consider

set_analysis_view -setup typical -hold  typical and

spefIn -rc corner rc_typcial $spef_dir/foo_qrc.spec_typical.spef and do the

timeDesign -signoff -reportOnly

Actually, I am unclear how timing analysis should be done in encounter when reading in externally generated SPEF in  MMMC mode. Any suggestion of the flow to do this will be highly appreciated. 

Thanks for your time.  

 

  • Kari

     The -qx_conf_file parameter of create_rc_corner is optional. You probably don't need it, unless there are some specific QRC settings you want. I normally don't use it. 

    Your second method should also work. As for whether you need to consider your "typical" corner as well as your worst and best, that is up to you! What do you really want to check for your timing signoff? For absolute final signoff, I would check setups and holds in ALL defined corners:

    set_analysis_view -setup {worst best typical} -hold  {worst best typical}

    spefIn -rc_corner rc_worst $spef_dir/foo_qrc.spef_worst.spef
    spefIn -rc_corner rc_best $spef_dir/foo_qrc.spef_best.spef
    spefIn -rc_corner rc_typcial $spef_dir/foo_qrc.spec_typical.spef

    timeDesign -signoff -reportOnly... etc.
  • diablo

    Thanks Kari. I was looking for the absolute final signoff and the command you posted is helpful. 


     

  • Scrivner

    Kari said:
    timeDesign -signoff -reportOnly... etc.

     

     What is the difference between -signoff and -reportOnly? The only thing I have found in the documentation says that both use the loaded SPEF information for parasitics instead of using the native RC extraction.

     

    Thx - Bart 

  • Kari

     Hi Bart,

     -signoff without -reportOnly will run QRC for you at that time. If you have run QRC separately and already loaded the SPEF files, or are using 3rd-party SPEF files, you need the -reportOnly switch so that timeDesign uses the SPEF data already in memory instead of trying to re-extract with QRC.

    - Kari

  • Scrivner

     

    Thanks Kari. I didn't realize -signoff ran qrc extraction internally. I've always run qrc separately and then used -reportOnly for timing analysis.

     

    Thanks again! 

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