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Constraint region overrides net based constraints

aricbeaver

Using 17.2 I have created a rigid-flex PCB. By default when a zone is created PCB Editor creates a constraint region around the perimeter of this zone. This is fine except when the nets within this zone require net based spacing requirements. PCB Editor seems to prioritize the constraint region over the net based constraints which ends up violating net spacing rules but no DRC is created. Is this normal? Is there a way of setting the priority of the spacing constraints?

Thanks!

  • oldmouldy

    The priority is fixed and documented in the Constraint Manager user Guide. In 17.2 use the Cadence Help and search the PCB Editor documentation for "override" it will be the first "hit", or get the "cmug" PDF from the Support site, in Product Documentation, "About Constraint Object Hierarchy" is the section that you need, both Inheritance and Override are documented.

  • aricbeaver
    in reply to oldmouldy

    Great. Thanks for the info. I read through it but don't see how to implement the override in the constraint manager. Are there instructions for that somewhere?

  • oldmouldy
    in reply to aricbeaver

    There is nothing to implement, this is how the Constraint Manager Overrides and Inheritance of rules works. From the Constraint Object Hierarchy diagram, you can see that (Constraint) Region based rules override Net based rules, Region Class and Region Class-Class rules are the only overrides for Region rules.

  • aricbeaver
    in reply to oldmouldy

    Interesting. My work around is to create another constraint region in a subsection of the larger region (entire flex zone) that uses the same spacing constraint set as the net based rules. Reasonable?

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