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techFile: Spacings constraint warning

kb how

Hi,

I was trying to construct techfile for layer ("RH" "drawing1") with minWidth or 0.36, but failed with below warning. The warning message indicated that the layer with purpose is not supported. Unfortunately, the constraint only apply on layer RH with drawing1 purpose. Enclosing some info as below (IC614.500.11)

techFile:

constraintGroups( ( "foundry" spacings( ( minWidth ("RH" "drawing1")  0.36   'description "minWidth RH"))))

 

CIW warning message:

*WARNING* (TECH-230014): techiSetLayerCst: In constraint group "foundry", constraint "minWidth" for layer "RH" uses custom purpose "drawing1".
                         Tools that follow strictly OpenAccess data usage intent might not support it.

I read through the document as found that this is the correct way in adding constaint spacing rule with layer and purpose. Please correct me if i'm wrong.

-How-

 

  • Any idea on this issue? Izzit layer with "drawing1" purpose is not adviseable to use?

  • Technically, the Open Access database does not support purposes in the same way you are used to Cadence supporting them. Purposes are supported by Cadence and handled by their own API. The warning indicates that any third party tool operating directly on the Open Access database might not support your layer purpose pairs as you expect. As Open Access handles layer information, it expects that all purposes on the same layer name should have the same rules and usage. There is no concept of metal1 drawing having different rules from metal1 HighVoltage, because in OA land, these are the same layer. You can only define width and spacing rules for metal1. However, Cadence allows you to differentiate between the two.

    That is my understanding.

    Here is a quote from the OA adoption guide:

    Virtuoso Environment Layer Purpose Pairs Support

    In the Virtuoso environment technology file it is possible to define technology rules for layer purpose pairs (LPP). For example, if you have a purpose named highPower for metal1 then you could define a different minimum width constraint for metal1 shapes with the highPower purpose from the minimum width for the metal1 layer shapes with no purpose specified.

    OpenAccess rules/constraints are only applicable to layers, not layer purpose pairs. Currently in the Virtuoso environment, any technology rule which is defined for a layer purpose pair is stored as a private extension and is available for Virtuoso applications. However, the private extension is not visible outside Virtuoso applications.

    Layer purpose constraints are supported in any constraint group. Although it is not permitted to define the same layer purpose pair constraint within a constraint group.

     

    Derek

  • Hi Derek,

     Thanks for the reply. Now i only know the lpps support in Cadence Virtuoso.

    By the way, if the layer with different purpose is needed and different constraint rule is apply. Will that causing any conflict? From what i have/tested, even though it prompts warning message during the techFile loading, the constraint rule that i set in the techFile is still valid (lpp). It is advisable for me to continue?

    Thanks a lot. :)

  • As far as I know, you should have no problems with that in Virtuoso. However, if you use a third party tool that reads your Open Access techfile directly, it most likely will not recognize the the constraint on your extra lpp. It will only recognize the constraint on the base layer.

    Derek

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