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defstruct in pcell (for layout), is it possible?

sjoerdh

Hello,

This is what I want to do:

  • Create a pcell that instantiates other pcells (layout)
  • Perform various "measurements" on this new instance (i.e.: retrieve the bounding box)
  • This information has to be used lateron in the pcell code

I'd like to store this information in a table, where each cell is a defstruct.The code looks like this:

procedure( genCurMir( ... )
    let( ()
        ...
        curMirInst = makeTable( "curMirInst" nil )
        defstruct( instance boundingBox gateCenter drainCenter sourceCentre )
        curMirInst["CELL1"] = make_instance()
        ...
        curMirInst["CELL1"]->boundingBox = instID~>bBox
        ...
    ) ;;; end of let
) ;;; end of procedure genCurMir

After generating the pcell (loading the code containing the command "pcDefinePCell") weird things happen: I am unable to open any view (layout/schematic/symbol/...).Entering commands in the CIW will result (9 out of 10 times) in an error, which is the same error when trying to open any cell-view:

*Error* setq/set: Variable is protected and cannot be assigned to - instance

I have tried creating the defstruct with an other name (blablablabla, definitely not used anywhere else), but the same error, only "instance" replaced by "blablablabla". I have to restart Cedence to regain control.

Furthermore, this created defstruct seems to be global, whereas I created it inside a let. I'd like to keep it local though.

So my question is:

Is it possible to use defstructs in pcells?
If so, what am I doing wrong?

I'd realy like to use this method (table of defstructs) since it is very conveniant.

Any help is highly appreciated.

Thanks in advance,

Sjoerd

Parents
  • sjoerdh

    Thank you Andrew,

    This was very helpful. Not only do I understand what I did wrong (why it did not work the way I thought it would work), but I know now how to make it like I want it to be.

    I'll definitely go for the t-o-t solution. Although there is nothing wrong with using defstructs (as you clearly explained), I'd like the idea to keep everything as local as possible (except for my own functions...). Appart from the creation/filling of the cells of the first table (either with a defstruct or a table), all other code is identical, so I can change it whenever I like to, and feel the need to.

    With kind regards,

    Sjoerd

Reply
  • sjoerdh

    Thank you Andrew,

    This was very helpful. Not only do I understand what I did wrong (why it did not work the way I thought it would work), but I know now how to make it like I want it to be.

    I'll definitely go for the t-o-t solution. Although there is nothing wrong with using defstructs (as you clearly explained), I'd like the idea to keep everything as local as possible (except for my own functions...). Appart from the creation/filling of the cells of the first table (either with a defstruct or a table), all other code is identical, so I can change it whenever I like to, and feel the need to.

    With kind regards,

    Sjoerd

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