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using nport in Verilog-AMS

TobiasM

Hi everybody,

I want to use a nport in Verilog-A/Verilog-AMS. The implementation has been done like this:
nport #(.file("/my_folder/my_device.sparam"), .interp("spline"), .thermalnoise("no"), .usewindow("yes")) N0 (BiasN, AVSS, BiasN_cm, AVSS, BiasP, AVSS, CBiasN, AVSS);
But when I try to simulate, there's this error that the file can't be found.
ERROR (CMI-2011): Unable to open S-parameter file `"/my_folder/my_device.sparam"'.

When I copy the path and try to open the file with emacs there's no error. So could someone tell me, where's my error in implementation or usage?

Thanks a lot,
Tobias

  • I suspect it's the way you are defining the path in the file parameter.  Try using a full path, rather than relative path.

    Also, it's good practice to designate your s-parameter files as mydevicesparam.s3p (or .s2p, .s4p, etc.).  Not a big deal, but if you later want to plot those s-parameters in ViVA standalone, you'll be able to do so.

     

    best regards,

    Tawna

  • Thanks for your advice. I now tried everything relating the way how to define the path. absolute (starting with /), relative (with ./) and, as the file is in a subdir of my home directory, with a ~/...../ .
    the solution with the ~/ is correctly substituted with my home path, as the error message points to the correct file.

    in my opinion, it is strange that the errormessage quotes the path twice, once with ` and then directly after the first quoting with " and closes then the " quote and the the '.

    Has anybody already implemented the nport in verliog-a or verilog-ams? could someone post a code snippet for example?

    kind regards,
    Tobias

  • Hi Tobias,

    With regards to setting your path, you may want to look at the following Solution:

    http://support.cadence.com/wps/mypoc/cos?uri=deeplinkmin:ViewSolution;solutionNumber=11066876

    Note that this is for the n2port...it will be the same for the nport.  In fact, you should use "nport" instead of "n2port", "n3port", etc.

    There shouldn't be any issues with nport and AMS-D (that I am aware of at this point).  You will definitely want to look at the nport appNote, however, to see how to set up parameters (if you don't set it up properly, you may not get the results that you expect).

    You can obtain the appNote at 

    http://support.cadence.com/wps/mypoc/cos?uri=deeplinkmin:DocumentViewer;src=wp;q=ApplicationNotes/Custom_IC_Design/NportAppNote72_8Jan.pdf
     
    If you continue to have issues, I recommend filing a Service Request through Cadence Support.  http://support.cadence.com .
     
    best regards,
    Tawna
     

     

     

  • Hi Tawna,

    Thanks for your fast replies. I've read now all the documents you mentioned. The Solution described in your first link ("Unable to open S-parameter file during Spectre run if path given is relative path") showed the error message if the file is not found. But in contrast to my error message, the file is only quoted by a ` and ':
    Unable to open S-parameter file `myspFile.s2p'.
    While my error message would look like this:
    Unable to open S-parameter file `"myspFile.s2p"'.

    Where could this come from, as I neet to quote the filename when instantiating the nport in Verilog-A?

    Regards,
    Tobias

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