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Can't probe terminal currents from symbols in PDK

mikewu

I am having trouble probing currents on terminals on transistors in a vendor's PDK. If I save a terminal current and try to plot it I get messages like "Unable to plot expression xxx because it does not evaluate to an object that can be plotted" and "*** is not a waveform object that can be displayed and will be DELETED automatically".

I can probe and plot terminal current on analogLib symbols no problem.

FWIW the Spectre views in this PDK seem to be blank, and previews of the symbol view in Library Manager have the word "PCELL" in the lower left corner.

Is this a PDK problem or am I doing yet another thing wrong in ADE Explorer that used to work in ADE-L? I have had other issues with this PDK (like no connectivity in Virtuoso-XL) so a PDK problem is a strong possibility.

  • This should work, and it's unlikely to be an issue with ADE Explorer versus ADE L. I also wouldn't expect this to be something to do with the PDK, because it's likely that this is just a hierarchical block - is there a schematic view as well - maybe that's a PCell too?

    It would probably be a whole lot easier if you contacted customer support, as then we could see what exactly the PDK looks like, what it is, and what is or isn't working.

    How are you probing the currents - via Outputs->To be Saved->Select on schematic and clicking the pins on the instance? Or some other way?

    Andrew

  • in reply to Andrew Beckett

    No schematic view.

    Yes, I am probing the currents via Outputs->To be Saved->Select on schematic and clicking the pins on the instance. Also tried Outputs->Save all... and selecting all device currents, then using direct plot on the terminal.

    The Layout-XL problem I am having with the same PDK give a warning:

    Could this be related? Or just a symptom that the PDK is not ready for prime time?

  • in reply to Andrew Beckett

    Dear mikewu,

    In addition to Andrew's valuable comments and questions, a couple of thoughts if I may intrude...

    1. Following your simulation, if you open the Results Browser, is there any output that appears to be a terminal current?

    2. If so, can you select it and right click the selected current and ply it?

    3. If you can plot it, right click the signal name again and send the output to the calculator, the resulting expression in the calculator window may be copied and used in your Assembler/Explorer set of outputs.

    Does this help at all?

    Shawn

  • in reply to ShawnLogan

    I was able to find the terminal current in Results Browser, plot it, and the rest of your suggestion. Thanks for the workaround.

    Sounds like a PDK problem that I need to communicate back to the vendor.

  • in reply to mikewu
    mikewu said:
    Could this be related? Or just a symptom that the PDK is not ready for prime time?

    I don't think the lack of a virtuosoDefaultExtractorSetup constraint group would have any effect whatsoever on ADE - ADE doesn't care about technology constraints (there are some design constraints that have an effect for optimisation and for Monte Carlo, but not technology constraints).

    It's a bit odd that there's a symbol and no schematic or stopping view. Something seems amiss, so I would contact the foundry.

    Andrew

  • in reply to mikewu

    Dear mikewu,

    mikewu said:
    I was able to find the terminal current in Results Browser, plot it, and the rest of your suggestion.

    Great! Thank you for letting us know!

    mikewu said:
    Sounds like a PDK problem that I need to communicate back to the vendor.

    As Andrew noted, I also don't believe the fact that your selected terminal using  this is a "PDK problem".  I would suspect there may be an issue with the terminal mapping in your amap directory (sub directory within the netlist). You can inspect the syntax of your saved currents in this subdirectory.

    Shawn

  • in reply to ShawnLogan

    Although the mapping in the amap directory is a consequence of the CDF information, which is a function of the PDK. I originally assumed this was a hierarchical block (since there's no stopping view), and if so the CDF wouldn't make a difference - but since it must be stopping at this point, it could be a problem with the termMapping in the spectre simulation information in the CDF.

    Lots of guesswork having to happen here - seeing the data would help enormously - hence my original suggestion to contact customer support.

    Andrew

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