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Nanoroute problem

amrzahir
I've a strange problem here, I'm using First Encounter to layout a digital design (about 300K standard cells design), targeting IBM 0.13u technology. What happens is after placement and Clock tree synthesis I use Nanoroute engine for routing, and then use timing optimization to meet time constraints. After running the optimization the results is excellent. But when I run timing analysis alone it gives a slack far from what results from the timing optimization ! I just want to know what is the problem. I doubt about the technology files but I need help please. BTW, I used wroute before with 0.35u technology and this didn't happen. Thanks

  • If I follow correctly, timing is reported as being met when optDesign -postRoute finishes, however when the design is re-timed after optimization has finished, timing is reported as *not* being met?  If that's the case- I'd wonder how timing is being reported.  Is it with "timeDesign -postRoute?  If so then it seems like a bug.  If not, try timeDesign -postRoute and let us know what you find.

    Either way, it sounds like you have a situation that would we could use to improve the software and/or learn from as users of the tool.

  • Thanks for your reply. I actually use (optDesign -postRoute) and yes what happens is exactly as you said. I need to know what is the difference between these two commands: 1) reportTA. 2) timeDesign. as the problem occurs with (reportTA) command, but when I used (timeDesign -postRoute) no slacks appeared. By the way, I make timing analysis from GUI (timing->timing analysis) and these are the results: After optDesign: (Worst Slack: -0.412ns) After timing analysis: (Worst negative slacks=-2.803) Sorry for long reply

  • reportTA has been obsoleted some time ago in favor of timeDesign.  In 8.1 I see it reported as an internal-only command:

    encounter 5> help reportTA
    Command 'REPORTTA' is for Cadence internal use only.

    timeDesign takes care of applying the recommended extraction settings depending on which stage in the process you're in (-preCTS | -postCTS | -postRoute etc).  I'd recommend sticking with timeDesign for these reasons.

    Thanks,
    Bob

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