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 Obtaining Slew rate from PSS 

Last post Wed, Feb 27 2008 7:11 AM by archive. 2 replies.
Started by archive 27 Feb 2008 07:11 AM. Topic has 2 replies and 1729 views
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  • Wed, Feb 27 2008 7:11 AM

    • archive
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    Obtaining Slew rate from PSS Reply

    I am trying to run a jitter analysis on a frequency divider. I have two ideal sources as my differential input from a VCO and am looking at the two output nets for the differential output voltage. I am running a PSS and Pnoise analysis.  Both simulations complete successfully. When I use Direct Plot to plot jitter I am told that, "slew rate data does not exist". However, I can plot the output voltage with respect to time and, using the calculator, plot the derivative of that voltage (which would be slew rate). So, it looks like PSS is just not saving SR in a place that PNoise knows to look for it...Am I missing some simple setting?


    Originally posted in cdnusers.org by OxBox
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  • Wed, Feb 27 2008 9:08 AM

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    RE: Obtaining Slew rate from PSS Reply

    OK - wild guess time. Do you have any "unusual" characters in your output net names? I've seen problems in the past with oscillator phase noise plots (I've not seen it with jitter, but not tried) where customers had + and - in the signal names. I'd count any non-alphanumeric (and "_") character as being unusual - and nets beginning with something other than a letter.

    Of course, this really should work, and can be fixed if it doesn't, but this is just a guess as to what might be the problem. Sometimes it's because the code to access the results doesn't go through the name mapping process which handles unusual characters...

    Regards,

    Andrew.


    Originally posted in cdnusers.org by adbeckett
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  • Wed, Feb 27 2008 11:30 AM

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    RE: Obtaining Slew rate from PSS Reply

    Alas, I removed the underscores so I had standard alphanumeric names on my output nets and the problem persists.Here are the exact errors I receive when trying to plot Jee from "pnoise jitter" in the Direct Plot Form:

    *Error* slew rate does not exist in data
    *Error* ymin: can't handle ymin(nil)
    *Error* ymax: can't handle ymax(nil)

    and when plotting Jc from "pnoise jitter" in the Direct Plot Form:
    *Error* Evaluating expression ((_drplRFJc ?from 1000 ?to 2000000000
    ?k 1000 ?multiplier 1 ?result "pnoise_pmjitter" ?unit
    "Second" ?event 0)).
    *Error* ("quotient" 10 t nil ("*Error* quotient: can't handle (drwave:179892904 / nil)"))

    Do you know where this slew rate is stored? I see the following output files:
    $SIMULATION_DIR/spectre/schematic/psf/pnoise.0.pmjitter.pnoise
    $SIMULATION_DIR/spectre/schematic/psf/pnoise.1.pmjitter.pnoise
    $SIMULATION_DIR/spectre/schematic/psf/pnoise.pmjitter.pnoise
    $SIMULATION_DIR/spectre/schematic/psf/pss.tran.pss
    $SIMULATION_DIR/spectre/schematic/psf/pss.fd.pss
    $SIMULATION_DIR/spectre/schematic/psf/pss.td.pss

    but they are in a format I cannot read with a text editor...


    Originally posted in cdnusers.org by OxBox
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Started by archive at 27 Feb 2008 07:11 AM. Topic has 2 replies.