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 Set Symbol parameters and pass parameters to its schematic device 

Last post Thu, Jan 10 2013 1:57 AM by Andrew Beckett. 5 replies.
Started by geeknerd 07 Jan 2013 01:35 AM. Topic has 5 replies and 970 views
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  • Mon, Jan 7 2013 1:35 AM

    • geeknerd
    • Not Ranked
    • Joined on Mon, Aug 6 2012
    • Posts 5
    • Points 85
    Set Symbol parameters and pass parameters to its schematic device Reply
    Hi all,

    We create a symbol from schematic.

    The symbol which we created has adjustable options for l and w (length and width).

    Now we use this symbol in other schematic and we want to set the l and w.

    We want to pass area value (l*w) to this symbol’s schematic device(for example, a diode).

    The spectre can accept parameters description.

    We want to substitute all parameters with real numbers because we want to do the LVS netlist output.

    Could you help us to solve this problem?

    Thanks for your help!

    Best regards, E-Jen
    • Post Points: 20
  • Mon, Jan 7 2013 1:42 AM

    Re: Set Symbol parameters and pass parameters to its schematic device Reply

     I answered a similar question in this thread last week. Set the diode to have the area set to pPar("l")*pPar("w"). The LVS netlist (CDL, I assume) would also have the expression (l*w) but that shouldn't be a problem for any LVS tool to be able to resolve during LVS.

    Regards,

    Andrew.

    • Post Points: 20
  • Mon, Jan 7 2013 3:28 AM

    • geeknerd
    • Not Ranked
    • Joined on Mon, Aug 6 2012
    • Posts 5
    • Points 85
    Re: Set Symbol parameters and pass parameters to its schematic device Reply

    Andrew, 

    Thanks for your help!

    We want to replace the function expression with real numbers because we have perl program to transfer the cdl output to Calibre LVS netlist format.

     We use PDK callback(from the other cell) to solve some function expression problem. 

    Unfortunately, there is no area callback function in the PDK. 

     Is it possible to write a simple callback to solve the problem?

     

    cellId = ddGetObj("library" "cellname" "cellview")

    procedure(calcSimParams(cellId)

        cdfgData = cdfGetInstCDF(cellId)

            tmpw=cdfParseFloatString(cdfgData->w->value)

    tmpl=cdfParseFloatString(cdfgData->l->value)

            cdfgData->area->value=sprintf(s "%g" (l*w))

    )

     

    Best regards,

    E-Jen 

    • Post Points: 20
  • Wed, Jan 9 2013 12:22 AM

    Re: Set Symbol parameters and pass parameters to its schematic device Reply

    But Calibre is perfectly capable of evaluating the expression - so why would you do this?

    A callback cannot solve this problem. If you have a block (say "myblock") which accepts CDF parameters w and l, and within myblock you have an instance of a diode which needs an area, as I said, the diode should allow the area to be set as pPar("w")*pPar("l").

    Imagine instead that you wanted to do this with a callback. You have two instances of myblock, one with w=1u,l=1u and one with w=2u,l=3u. If you (somehow) set the area on the diode instance inside myblock to be w*l for one instance, it will be wrong for the other. Potentially you could have a pseudo-flattening netlister which creates a separate subckt for each variant, but that's a lot of work (I wrote one of these many years ago (about 20) when Dracula's expression evaluation didn't really work yet), and complete overkill when the Verification tool can evaluate the expression. Essentially you need the expression to be evalated as the design is elaborated in the tool that reads the netlist - be it the simulator or the LVS tool.

    Regards,

    Andrew.

    • Post Points: 20
  • Thu, Jan 10 2013 1:52 AM

    • geeknerd
    • Not Ranked
    • Joined on Mon, Aug 6 2012
    • Posts 5
    • Points 85
    Re: Set Symbol parameters and pass parameters to its schematic device Reply
      Thanks for your help!

    Now we have a new problem.

    When we try export cdl file, the output netlist will stop on this new created device.

    One line of the output file looks like as follows.

    “XI7 net20 VIN VSS VSS VDD subcircuit”

    How could I export the whole schematics?

    Thanks and best regards,

    E-Jen 
    • Post Points: 20
  • Thu, Jan 10 2013 1:57 AM

    Re: Set Symbol parameters and pass parameters to its schematic device Reply

    E-Jen,

    It sounds as if you must have the incorrect switch or stop view list setup. You need to ensure that the switch list contains the name of the view to switch into, and that it doesn't have a stop view listed before the schematic view.

    If you still have a problem, please contact customer support so that somebody can look at your data to understand what is wrong with your set up. This is pretty straightforward and not unusual though, so I'm sure it's just something wrong in how you've told it to netlist.

    Regards,

    Andrew.

    • Post Points: 5
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Started by geeknerd at 07 Jan 2013 01:35 AM. Topic has 5 replies.