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dummy device finder

varunkumar
Can you send me a skill code to find the Dummy devices (MOS,RESISTOR etc) in layout 
  • You didn't give any clue as to which tool or version you are using (are you adding dummies in modgens maybe?), but in general how would anything know whether something was a dummy or not?
  • Dummy device is defined as  " all terminal is connected to same potential (vdd,gnd ,or some net potential)"  It can be MOS,BJT or resistor usually we use for matching devices  to provide the same environment (we use modgen but not always) .I am using Cadence virtuoso IC 6.15 .Can you help me in coding since I am new to skill and dummy finding is very time consuming for old databse.
  • I'm presuming that the layout was done with XL so that there will be connectivity info in the database?

    It really helps to give sufficient info when you make requests on the forum otherwise we waste a lot of time and effort seeking clarification.

    Thanks,
    Andrew
  • Sorry for incomplete information. No connectivity is maintained and layout is not in XL it is in L editor .

  • That's not going to be so easy then. I had thought you might be able to do:

    lceExtract(cvId) ; to use the Virtuoso Layout Suite XL extractor
    dummies=setof(inst cvId~>instances
      firstNet=car(inst~>instTerms)~>net
      firstNet && forall(instTerm cdr(inst~>instTerms) instTerm~>net==firstNet)
    )

    But even that's not quite right. The problem is that lceExtract will probably not work in general if there's no schematic source, or on partly laid out designs. 

    Fundamentally you're going to have to extract the connections from the device and see whether the nets are all the same for all instTerms - something like that. If it had been done with layout XL, something like the above would be relatively straightforward (it would need some refinement to ensure that all the instTerms are actually present).

    Andrew.

  •  Without connectivity in the database, SKILL will have a hard time finding connections of the shapes/cells. You have to traverse the hierarchy and track the shapes on an instance by instance basis.

    I would use the LVS commands in Diva, PVS or other LVS tools to trace the connections through the hierarchy. They can then place a marker on the dummy devices. Not only wll it be easier to code but will be much faster because the tracing is built in.

     Ted

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