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Cdsenv setting with Backannotation in LayoutXL

Jinhyung

Hi, thanks for your time.

I have a few questions with the 'backannotation' in Layout XL.

1. lxDummyBackAnnotateMFactorName

I want to know what this setting is. 

I found that when I make instances to freeze pcell, make dummies with "create dummy with net" , and wirte "m" to the value of "lxDummyBackAnnotateMFactorName" in the Cdsenv Editor,

then, the dummy instances are insered with mulit factor in Schemaic when the backannotation is executed.

However, if I don't wirte any value of "lxDummyBackAnnotateMFactorName", then instances which is made by freeze pcell in Layout is not inserted with multi factor.

The point is, I want to know that "lxDummyBackAnnotateMFactorName" is only for backannotating the freeze cells with multi factor, or there is another usage with "lxDummyBackAnnotateMFactorName".

2. lxDummyBackAnnotateMissingTerm

In 'Cadence Help', it says "Allow dummies to be backannotated when the layout instances has missing terminals compared to the schematic".

However, I can't find any differences whether the turn on the setting "lxDummyBackAnnotateMissingTerm" or not.

So, I want to know what situation this setting works.

3. Instance property with dummy

When I execute the "Create dummy with net", then two options are made, "lvsIgnore", "ignore".

I think these options are for ignoring these dummies in LVS, but not clearly understood.

So, I want to know what thess options are for?


Best regards.

  • Re. Freeze Pcell: This creates a new (fixed) cellview in the designated library. The default is for a unique cellName for each instance. So what are you doing? Creating one frozen dummy then re-referencing other occurrences. Dummies can be mFactored when reconginsed as dummies (appropriate properties) with matching parameters.

    Why are you freezing the dummies?

    Re. ignore/ lvsIgnore: 

    Virtuoso Layout Suite XL: Connectivity Driven Editing User Guide -- lvsIgnore Property (cadence.com)

    Virtuoso Layout Suite XL: Connectivity Driven Editing User Guide -- ignore Property (cadence.com)

  • Certainly, let's address your questions regarding the "backannotation" in Layout XL:

    1. lxDummyBackAnnotateMFactorName:

      • lxDummyBackAnnotateMFactorName is used for backannotating instances that have a different scale factor (multiplying factor) than what's in the schematic. When you set a value for this parameter, it indicates that you want to apply a specific scale factor during backannotation.
      • If you set lxDummyBackAnnotateMFactorName with a value like "m," it suggests that when you backannotate dummies created with a certain net association, those dummies should be inserted with a particular scale factor. This can be helpful when you need to adjust the scale of instances during backannotation.

    2. lxDummyBackAnnotateMissingTerm:

      • lxDummyBackAnnotateMissingTerm comes into play when there are discrepancies between layout instances and the schematic, specifically regarding missing terminals. When enabled, it allows dummies to be backannotated even if there are missing terminals compared to the schematic.
      • For example, if your layout has instances that don't have all the terminals that the schematic expects, enabling this setting will still allow backannotation to proceed, and it may insert dummies to account for the missing terminals.

    3. Instance Property with Dummy:

      • The options "lvsIgnore" and "ignore" are often used for dummies to control their behavior during LVS (Layout vs. Schematic) verification.
      • lvsIgnore: When set to "true" or checked, it indicates that the dummy should be ignored during LVS checks. This is useful when you want to exclude certain dummies from LVS verification because they are intended for purposes like physical design and not electrical connectivity.
      • ignore: This option is similar to "lvsIgnore" and can be used for similar purposes. It's essentially a way to specify that certain dummies should not be considered during LVS checks.

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