Stats

  • Locked Locked
  • Replies 7
  • Subscribers 165
  • Views 17358
  • Members are here 0
More Content
This discussion has been locked.
You can no longer post new replies to this discussion. If you have a question you can start a new discussion

Changing Diff Pair Primary Gap

Lenny PCB

I changed my primary diff pair primary gap from 8 to 10 mils and closed the CM and expected to see DRC's to fix but did not. I'm a newer user and stated using Allegro 16.2 from 16.01. I would expect to see a apply button but just click file close but it appears the changes did not update. I go back into the CM and the changes are listed. Any help would be appreciated. Thanks.

  • oldmouldy

    The CM settings will get applied "immediately", even if the CM is not closed.

    Try Updating the DRCs? but I guess that you tried that already.

    Check what constraints are active, Display>Constraints, left-click and drag a box around the pair, you should get the active constraint and values in the pop-up window.

    Make a temporary setting of a much larger value, like 25mil, that should flag some errors.

    If any of that doesn't lead to some resolution, you will probably need to get this reported to Cadence Support through SourceLink.

  • Lenny PCB

    I had done all of the above except the temp setting of 25 mil. I tried that and that did not produce DRC markers either. I set it back to 10mil and discovered if I pic a cline on a diff pair and "slide" it the gap jumps to 10mils. I will report this to SourceLink.

     

  • redwire

    Interesting...I tried your test in 16.01 and it crashes every time (I guess I have to submit a bug report).  I tested in 16.2 and it's okay.

    Anyway, the diffpairs are tricky.  What's missing is the Uncoupled Length and Gather Control is not set.  Change it in the Electrical Constraint Set (if that's how you do it) to Include and then add a value which covers the gap getting in and out of pads that are further apart than the gap allows.


    I am providing an example board that you can play with and see the errors pop up immediately when you change the spacing.  Open the CM and change the primary gap.


    HTH

    diffptest.zip
  • Lenny PCB

    I did have some nets with Uncoupled Length and Gather Control set so I set them all but DRC's still not showing up. I played with your test file with 16.01 the DRC's show up. When I change the gap using 16.2 it crashes. I'm still learning this software so I'm no expert. I submitted a SR and for now using "Slide" is my get around.

  • redwire

    Regarding the crash, that sounds *too* familiar.  I had already applied the hotfixes to 16.2 before testing with it.  Once I applied the latest hotfixes to 16.01 the crash stopped.  I would like to hear the results of your SR.

     

    So, if my test is working on one code version and yours is not, it still sounds like a setup problem.  Can you generate a similar test file like I did so I can play with it?  Did you set the "Analysis Modes" in the CM?  Check mine vs yours.

    Regards,
    Bill

Cadence Guidelines

Community Guidelines

The Cadence Design Communities support Cadence users and technologists interacting to exchange ideas, news, technical information, and best practices to solve problems and get the most from Cadence technology. The community is open to everyone, and to provide the most value, we require participants to follow our Community Guidelines that facilitate a quality exchange of ideas and information. By accessing, contributing, using or downloading any materials from the site, you agree to be bound by the full Community Guidelines.