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How to place an instance regardless of its SITE definition

jgentry

All,

  I have some instances that need to be rotated 90-degrees from their "normal" orientation.  However, when I try to placeInstance, dbPlaceInst and even set R90 from the attributes menu, it always tells me that it is reseting to R0 because the desired orient, R90, doesn't match the CORE site definition (the SYMMETRY line in the LEF is 'X Y R90' and, thus, isn't preventing the rotation itself).  Is there a way around this other than to create some DEF with the desired inst locations and R90 orients (which works by the way)?  

Thanks,
JG

  •  Are you talking about std cells? They can only go on a matching row/site. Can you explain a bit more why you're trying to do this? Maybe there's a different solution.

  •  Kari,

      Yes, it is a stdcell.  It's a filler cell actually.  We have sections in our chip where we put in a clean supply grid but it has to route orthogonal to the normal core power grid in order to provide adequate shielding for reference clock routes.  I was hoping there was some switch somewhere to tell the *place* commands to just do it (I was hopeful that dbPlaceInst was the command that would ignore any site definitions).

     

    Thanks,
    JG

  •  So you have an area (or areas) in your chip where the cells need to be R90 from the rest of the design... sounds like that area should be a partition, but without really knowing your design it's hard to say. You *could* try this: make a copy of the filler cell LEF, give the cell a different name, and make it CLASS BLOCK. Make sure the SYMMETRY statement allows R90 orientation. Then you should be able to place this new cell however you like (but you'd have to place it by hand or with a script).

  •  Thanks Kari.  Looks like an "easy" solution isn't available.  I've already started work on my custom DEF generator to support instances as well as the normal vias, pins and special nets.

    Thanks,
    JG

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