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 Allegro Constraints-relative propagation delay 

Last post Mon, Apr 8 2013 6:03 AM by mcatramb91. 3 replies.
Started by Redskins 05 Apr 2013 12:28 PM. Topic has 3 replies and 1235 views
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  • Fri, Apr 5 2013 12:28 PM

    • Redskins
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    Allegro Constraints-relative propagation delay Reply

    Can someone explain in general what the definition of delta/tolerance is when adjusting for matched lengths in the constraint manager in Allegro? Thank you!

    • Post Points: 35
  • Mon, Apr 8 2013 12:24 AM

    • tltoth
    • Top 50 Contributor
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    Re: Allegro Constraints-relative propagation delay Reply

     Difference in length of the traces in units of mil (mm etc.) or in percentage.

    • Post Points: 20
  • Mon, Apr 8 2013 6:02 AM

    • Redskins
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    Re: Allegro Constraints-relative propagation delay Reply

    Thanks, could you please give me a little detail please...Let's say I have a constraint setting of 5:100 vs 25:100, please explain the difference...Thank you!

    • Post Points: 5
  • Mon, Apr 8 2013 6:03 AM

    • mcatramb91
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    Re: Allegro Constraints-relative propagation delay Reply

    Here is a recent thread on this topic that may be able to answer some of your questions:

    http://www.cadence.com/Community/forums/p/24764/1318896.aspx#1318896

    Setting the Delta:Tolerance field to 0.000mil:100.000mil means the longest net in the group could be 100mils longer than the target net and the shortest net in the group could be 100 mils shorter than the target.  So across all the nets you could have a variance in length as much as 200mils before seeing a DRC. (+/-100mil)

    Setting the Delta:Tolerance field to :100.000mil (blank Delta field) means that all the nets could have a variance in length as much as 100mils with no specific Target.  This is sometimes harder to match the members and could cause you to overly lengthen the nets. 

    Hope this helps,
    Mike Catrambone

    • Post Points: 5
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Started by Redskins at 05 Apr 2013 12:28 PM. Topic has 3 replies.