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Using layout-only (physical) instances in Virtuoso XL

Lynks

Using IC6.1.5-64b.500.8, I have a core design that has a schematic view and when I want to create the physical view, I would like to use a physical-only instance to help create the physical view. This physical-only instance is really a fixed arrangement of pads and wires with no connectivity information but when I connect a net to it at the top-level, I would like Virtuoso XL to recognize that a net should continue to form through these physical-only instances. I guess you can say the physical-only instance is a common template to help wire-up my core design and any other variations of the core design. I expect to tweak this template once in a while if I have to shift some pads or wires for whatever reason.

 The non-ideal solution is to place the physical-only instance and flatten it so when I work on the rest of the layout, Virtuoso XL can recognize the connections I'm making. It won't recognize these connections if I keep it as an instance even after I go to Options->Layout XL->Extraction and set "Extract connectivity level" to sufficiently high level. However, this works if I place a matching pin inside the physical-only instance using the same net name that I expect to use at the top-level, but this may not always be the case. It would be great if it could somehow inherit the net from the top-level when I connect/overlap a wire from the top-level.

 The drawback of the flattening method is that if I want to update the physical-only instance, I need to delete all the flattened elements and re-instance the updated element... then I would have to do this for every design variation that used this physical-only instance.

Furthermore, Virtuoso XL warns me that the physical-only instance has no corresponding element on the schematic and it's right because it's merely just a bunch of wires and pads that will be used as connections. I'd just right click the instance in the Navigator panel and click Add Ignore for Check but I still would like Virtuoso to check if I accidentally made shorts/incomplete nets/etc.

Is there a better way to use physical-only instances when designing the layout of a schematic-based design in Virtuoso XL?

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  • I can't say how the .8 is behaving since I don't have it here at the moment. But if the envVars are available it should work.  I made a quick check with my .17 to see if it does work for me.

    I created two Pins on Metal1, both named "A", the tool will show me the flightline for the uncomplete net between them. Then I create  some wiring starting and ending with Metal1 ( to keep it simple :)  ) and pushed that wiring into a cell with the "Make Cell" command.
    Now I overlap my A pins with the wiring in that cell and my flightline is gone and the tool is showing the net as complete.

    Please try to repeat that simple test before you start with the more complex real example.

    If it is still not working try to get a newer IC version.

     

    Edit:  Do you realy need 5 levels extracted? Be aware that the tool is chasing all the shapes through that hierarchy, which can hit your performance a lot. Only extract what you realy need.

Reply

  • I can't say how the .8 is behaving since I don't have it here at the moment. But if the envVars are available it should work.  I made a quick check with my .17 to see if it does work for me.

    I created two Pins on Metal1, both named "A", the tool will show me the flightline for the uncomplete net between them. Then I create  some wiring starting and ending with Metal1 ( to keep it simple :)  ) and pushed that wiring into a cell with the "Make Cell" command.
    Now I overlap my A pins with the wiring in that cell and my flightline is gone and the tool is showing the net as complete.

    Please try to repeat that simple test before you start with the more complex real example.

    If it is still not working try to get a newer IC version.

     

    Edit:  Do you realy need 5 levels extracted? Be aware that the tool is chasing all the shapes through that hierarchy, which can hit your performance a lot. Only extract what you realy need.

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