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  3. Pcell Inherited Connection

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Pcell Inherited Connection

kdolan
kdolan 10 months ago

Hi! 

I am attempting to create a very simple test pcell that contains a single Nmos 4 terminal device (Gate, Source, Drain, Backgate). However, unlike other devices I have used in the past, the backgate terminal of the device I wish to include within the pcell is an inherited connection, and the other 3 are physical terminals. Note that for the pcell master, I do not want any inherited connections, just physical pins. Hence I need to drive this inherited connection with a pin within my pcell. I started implementing the symbol and schematic first, ensuring I could obtain the correct connectivity, extract netlist, etc. I thought I had it hooked up correctly, but alas I am failing to export the CDL. Let me explain my current approach.

Schematic:

Create the 4 physical pins using a combination of dbCreateInst (for the pin isnt), dbMakeNet, dbCreateTerm and dbCreatePin.

Create the device instance using dbCreateInstByMasterName and setting the desired cdf parameters + callbacks.

For the physical terminals of the device, I'm using dbCreateConnByName to make the connection to the appropriate net that was created above.

For the inherited connection, I am creating a netSet property like so: dbCreateProp(newinst deviceTermName "netSet" netName)

Symbol:

Create the 4 physical pins using a combination of dbCreateRect, dbMakeNet, dbCreateTerm, dbCreatePin.

And then create whatever symbol design I wish using the likes of dbCreateRect, dbCreateLine, etc. 

Everything works fine when using a device without an inherited connection, so I'm guessing I'm missing something along this line... Also, if I copy the contents of the pcell schematic to a regular schematic view, do a check and save, the view extracts just fine. So I wonder if the check and save it fixing the connectivity that I may not have. 

Thanks for any possibly engagement or suggestions Slight smile

Keelan

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  • henker
    henker 10 months ago

    What about dumping the schematic after C&S and check what is in there and not or different in the pcell code (dumping e.g: dbWriteSkill(geGetWindowCellView() "cellview.il" "w" "4.4") )

    Since you say that it just does not work with the inherit, than it might just be the inherit: e.g.
    dbCreateProp(newinst deviceTermName "netSet" netName)

    Are you sure that the inherit property name that you want to redirect is same as a terminal name? That actually would render the inherit useless.
    e.g. for the inherit [@sub:%:SUB!] the correct netSet call would be: dbCreateProp(newinst "sub" "netSet" netName)

    However, for this simple approach here (no dynamic changes on pins or circuit structures), it might be easier to just use a simple schematic with pPar parameters on the instance. That would probably have same functionality without the pcell hassle.

    Regards,

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