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Creating exceptions to keepouts

IainFK

Hi all

Using Allegro 16.6, I want to create a via keepout area that will only allow GND vias, and give an error if any other net is in there. Is this possible? This is for an area of the board that will be in contact with the case, so GND vias are fine (and indeed desirable) but anything else presents a shorting risk. There are other occasions where an exception to a keepout would be useful so any ideas would be much appreciated.

Thanks

Iain 

(not Lain)

  • steve
    Sort of - take a look at:- http://orcad.co.uk/images/PDF/net_areas.pdf
  • Soundman99

    There is a support case for this, it's called "Allow certain nets only in a route keepout area with no DRCs".  Basically, you go in and create a Physical Spacing constraint set that doesn't allow any etch, and then another that does.  You create a net class with your GND net/s in it.  Then, in your region, you assign the region the no-etch PSC, and on the class that contains your GND net/s, you assign it a PSC that allows etch.  

    I don't know if the link here will work, but this might bring you right to the article on how to do it.

    http://support.cadence.com/wps/myportal/cos/COSHome/viewsolution/!ut/p/a1/tY_NDoIwEISfxbumW0QKx_oTEFCiYqRcDGijRFsIgok-va0x8aSe3NvOfjuzi1KUoFRm1-KQNUUps7PuU2s7xRMTexH4rkNHQIEs_HWAjYAMFMAUAB-Kwq_9DUqfyBcHpiLI28MOQweoG1hLj8R9iAhay7IW6tiV9tpzXoWFPCHW1C3XyrjctYLLJr5VXKn55djIQ3df6NmlPLf61Xkrcl4jhjEBCxz7FTrwxib4gP1oaBCgXmy65jzEEBl_Ca1EAj0m7L7YzmKe3yntdB5aw6Wt/dl5/d5/L2dBISEvZ0FBIS9nQSEh/ 

    ~ Pat

  • IainFK
    Thanks for the help guys, works fine (if a little convoluted!). The only other aggravation was that I couldn't create a void within the constraint shape (which needed to be like a square doughnut) so had to do it with overlapping shapes.
  • mcatramb91

    Hi,

    What I have done in the past is to create a Static Shape assigned to GND in the area.

    This would allow GND Vias to contact the shape and DRC Vias which are not connected to GND.

    Hope this helps,
    Mike Catrambone

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