Setting Pair to Pair constraint in Allegro 15.5

Not sure about 15.5 (it may be the same as 16.x) but use Constraint Manager, Spacing constraints and use Net class - class to define your diff pairs and space between them.

Not sure if you still needed an answer, but in the event that you do, see below. 

There are probably other ways (likely more elegant) to do this, but what I have done in the past is to apply a NET_SPACING_TYPE to the pairs that is indicative of what you are trying to accomplish.

For example, let's say you are talking about some diff pairs in interface IntX that want to be 12mils from other IntX pairs and 20mils to anything else. You might set NET_SPACING_TYPE = IntX_12_20 to note that the spacing should be 12mils to other signals that have this spacing type and 20mils to others. Depending on the situation, this may be quite a chore to configure in the assignment table, but will ultimately get the job done.

If you were looking for a property that you can assign to set the spacing to any other diff pair, I don't think something like that exists.

Hi Eric,

I do agree that Attaching a particular NET_SPACING_TYPE will resolve the problem. But i use to get Line to Line error between the diffpairs if the primary gap is more than line to to line spacing in spacing rule set.

I was looking for some solution which can supress this DRC. Because the etch editing becomes difficult with more DRC's and some times it even hangs Allegro.

Seems to be like Environment variable " drc_diff_pair_overide = 0 " Under Drc in User preference Editior can supress this DRC.If any you have tried please suggest your thoughts?

Thanks in advance,

RMB

Hi All,      
      
Can anybody explain me how to set Differential Pair to Pair constraint in Allegro 15.5?

 Hi RMB, Eric, others...

 NET_SPACING_TYPE is the correct net property to control the pair to pair space.  IF you get line to line DRCs between the P and N traces of the net, this means you haven't properly configured the diff pair in the electrical section of Constraint Manager so Allegro doesn't recognize the pair as a diff pair.