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Ignore property for schematics ( LX binding )

frankliu

lxSelectedUpdateIgnore works on layout instances.

There does not seem to be an equivalent "ignore" function for schematic instances...

Here is the scenario:

Typically in layout there are elements which are artifacts of the layout, i.e. they may be dummy transistor cells which are required by the technology.

In many of these instances, when I insert such layout instances I break VLX correspondence, and have to set the ignore property on these "dummy" cells.

Eventually I have to add them into the schematic to pass LVS, but in doing so, again I break VLX correspondence (this time from the schematic side).

After adding these "dummy" transistors in schematics (and breaking the correspondence), if I were to Update from source, the dummy transistors

will be instantiated in the layout, and setting the binding between the "dummy" layout instances and the corresponding schematic instances is normally

not feasible (it is possible, but in general dummy cells from a given library typically don't contain any connectivity information, i.e. net/terminal/pins).

Hope this makes sense, in general it seems it would be useful to have the ignore property on the source side as well.  But perhaps there are other 

approaches that circumvent these issues.  I know it is also possible to have two different schematic views associated with one layout, but having two

views adds more complexity and becomes more error prone, I rather just have one schematic and one corresponding layout view.  If you have other

suggestions please let me know.

Thanks in advance,

-f

  • All that function does on the layout side is to set the "ignore" property to true on the layout instance. You can equally well do the same on the schematic side - it's just that function that doesn't work.

    You can select the instance(s) on the schematic side and do:

    geGetSelSet()~>ignore=t

    and they won't then get checked, or update components and nets won't see them. 

    Another approach is to Launch->Configure Physical Hierarchy and then you can set the attribute there (so it's stored in the physConfig rather than needing the schematic to be edited).

    The other flow you could investigate is to select the instance on the layout side and use Right Mouse->Create Dummy with net. This will set all the properties as needed on the layout device. You can then use the Connectivity->Back Annotate menu to add these back into the schematic. May not be what you want, but worth looking at.

    Regards,

    Andrew.

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