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 16.2 - Can't change impedance value in cross section 

Last post Tue, Jan 13 2009 8:48 AM by redwire. 9 replies.
Started by Critter1 07 Jan 2009 10:19 AM. Topic has 9 replies and 4309 views
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  • Wed, Jan 7 2009 10:19 AM

    • Critter1
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    16.2 - Can't change impedance value in cross section Reply

    When I try to change the impednace value in the cross section menu, it is stuck on 60 ohms.  Any suggestions?

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    • Post Points: 50
  • Thu, Jan 8 2009 6:49 AM

    • Ejlersen
    • Top 10 Contributor
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    Re: 16.2 - Can't change impedance value in cross section Reply

    What tier of Allegro/OrCAD are you running.

     Try using Tools, Setup Advisor, Next, Cross-Section.

    If you cannot change the impedance and get the trace width calculated then you're running either OrCAD PCB Designer Basics, OrCAD PCB Designer or Allegro PCB Design CIS L. In that case you will have to do it the other way around. Type in a trace width and notice that the impedance is calculated. This way you can interpolate to the impedance you want to and use that in your constraint set.

     

    Best regards,

    Ole

    Best regards Ole
    • Post Points: 20
  • Thu, Jan 8 2009 7:50 AM

    • Critter1
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    RE: 16.2 - Can't change impedance value in cross section Reply
    Ole,

    We are using Allegro PCB CIS L with the performance option and no SI licenses.  I have upgraded to the latest ISR too.  I have been working with Tech Support and as it turns out, it is a bug that is supposed to be fixed on the next ISR.  It's only a problem if you don't have any of the SI licenses installed with 16.2.

    I tried going the way you suggested (typing in a trace width) but it is still stuck on 60 ohms.  I still have 16.01 installed so I believe I am going to “down rev” the board and continue on with 16.01 until this issue is fixed.

    The only other way that I know to get around this in 16.2 is to set the “acon_no_impedance_width” property in user preferences, route, connect.  If this option is on, impedance rules will have no effect on the trace width in add connect.  You will have to use a external impedance calculator (online or purchased) to calculated your trace\space values for diff. pairs and apply those values in the constraint manager for each layer accordingly.  It’s a little more work but it will do.

    Mike Crittenden
    • Post Points: 5
  • Thu, Jan 8 2009 8:15 AM

    • Critter1
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    RE: 16.2 - Can't change impedance value in cross section Reply
    Ole,

    I stand corrected, you are right.  I went to Tools, Setup Advisor, Next, Cross-Section and I am able to change the impedance values and trace widths using your suggestion.  I tried Setup, Cross-Section and the values are correct but as soon as I try to change them, it goes back to being stuck on 60 ohms.  I will use your method until Cadence fixes this.

    Thanks for your help!

    Mike Crittenden
    • Post Points: 35
  • Thu, Jan 8 2009 8:20 AM

    • Bennigin
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    RE: 16.2 - Can't change impedance value in cross section Reply
    Is anyone else receiving double emails?
    • Post Points: 20
  • Thu, Jan 8 2009 8:26 AM

    • Critter1
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    RE: 16.2 - Can't change impedance value in cross section Reply
    I am.

    Mike Crittenden
    • Post Points: 5
  • Thu, Jan 8 2009 9:34 AM

    • Ejlersen
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    Re: RE: 16.2 - Can't change impedance value in cross section Reply

    Hi,

    I reported the issue a month ago and new that it would work using Tools-Setup Advisor.

    Don't know why, but that cross section editor somehow it different from the other one.

    Best regards,

    Ole

    Best regards Ole
    • Post Points: 5
  • Thu, Jan 8 2009 9:58 AM

    • pcbgeorge
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    RE: 16.2 - Can't change impedance value in cross section Reply
    Me too...
    • Post Points: 5
  • Tue, Jan 13 2009 8:42 AM

    • redwire
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    Re: 16.2 - Can't change impedance value in cross section Reply

     All,

    I am posting this in response to contact by EMA regarding this.  This is my test case that fails to correctly display the impedance.  I have posted screen shots as well as the test board.

     

    Note: all of us complaining are using the Performance L license (most with hotfix).

    Anyone out there reading this with a higher level license that can "see" the correct impedance in the test board?

    HTH,

    Bill

    • Post Points: 5
  • Tue, Jan 13 2009 8:48 AM

    • redwire
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    Re: 16.2 - Can't change impedance value in cross section Reply

     And here is the same board down-rev'd to 16.01 and the parasitics and cross section results.

    • Post Points: 5
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Started by Critter1 at 07 Jan 2009 10:19 AM. Topic has 9 replies.