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Controlling hierarchical design net names

AmarAgnihotri

I am using OrCAD 10.3 for a hierarchical design where one schematic is instantiated multiple times. When I generate allegro netlist the net names used inside this instantiated schematics changes, it remains same only for one instance and suffixes some unique number "_xxxxx" to net names in other instances. How do I control the net names in the instantiated schematics? I want to attach CSet property to these net name, and with this behaviour it becomes very difficult to attach CSet property.

  • oldmouldy

    The tool will ensure that the netnames in the repeated hierarchical blocks are given unique names. If you want to assign unique names to the nets in repeated schematics you will need to flatten the design to use repeated pages.

    This is not really a major issue since "some_net" and "some_net_XXXX" would likely want to have the same CSet attached.

  • AmarAgnihotri

     Thanks for your response. From your answer, it seems like there is no control over "_XXXX" in OrCAD and this is completely tool driven naming (suggestion: it would have better, if there was some "net name suffix" property in the hierarchical block property window for this kind of naming purpose. Gives more control over design).

     Your assumption about having same CSet to all the nets is not true in most of the cases. For example: in my case where hierarchy is logical in schematics and does not mean to be same physical layout because of board area restriction. A unidirectional source synchronous data bus will have different min/max length CSet for different hierarchical blocks if their placement is not identical on PCB.

    The worst part of the unique name suffix  is, it is purely unique! There is no relation between the names of the two nets in a same bus for a given hierarchical block.

    Question: In OrCAD, you can actually specify unique CSet names to nets for different hierarchical blocks. But I could not figure out the way to export this information in Allegro netlist. How do we achieve this?

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