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ADEXL Save all currents

PNadeau

Dear folks,

I am trying to save all currents entering the pins of schematic instances up to a certain level for a Spectre PSS simulation.

In ADEXL, I right click in the outputs table somewhere, click Save All, and configure: Save device currents -> selected, subcktprobelvl->3, useprobes -> yes.

If I run a DC simulation I get the correct behaviour (currents saved up to a certain level, I can see it in the Results Browser)

If I run PSS, no currents are saved.

This is the relevant line that appears in the netlist

saveOptions options save=all currents=selected subcktprobelvl=3 useprobes=yes

Anyone have an idea how to save all currents in PSS?

Thanks in advance,
Phil

  • Andrew Beckett

    Phil,

    I'm surprised. That would work (I just tried it, and it works for me). Which version of IC and MMSIM are you using? (including subversions)

    Thanks,

    Andrew.

  • PNadeau

    Thanks for checking.  It's odd, I just started a completely new testbench with a few levels of hierarchy and it seems to work perfectly.  But I have a bunch of testbenches where it still does not work (settings in the Save All dialog in both cases look identical).   Perhaps there is an interacting setting somewhere.   For what it's worth I have IC6.1.7-64b-78 and MMSIM 15.1.0.284.isr1.  I'll see if I can replicate the steps or setup that leads to the problem...

  • PNadeau

    Ok, so the interacting setting is Spectre APS.  I start with the testbench that saves all currents properly all the way down the hierarchy, but then I enable APS and the instance currents are no longer saved.  

    It still saves terminal currents for certain cells (like AnalogLib caps, resistors, and my PDK devices), but will not save currents into the terminals of my custom cell blocks. Does this give an idea?

  • Frank Wiedmann

    I suggest you try setting "Instance Preservation: All" in the High-Performance Simulation Options.

  • Andrew Beckett

    I suspect this is an optimisation performed because using subcktprobelvl is expensive - you can end up with a lot of iprobes in the circuit which can significantly impact performance (particularly with PSS). That said, it does this silently and there doesn't seem to be a way to disable it (the instance preservation that Frank suggested doesn't work - I wouldn't have expected it to). 

    The workaround is to explicitly save the currents you want. Unfortunately even if you select currents using Outputs->To be Saved->Select by Subckt Inst and tell it to save a certain depth of currents, that doesn't work either - you have to explicitly save all the currents you want.

    This may be an oversight - because with transient it works fine - as soon as you add pss, it breaks. So please contact customer support about this. I didn't see any reports of this issue so far.

    Regards,

    Andrew.

  • PNadeau

    Thanks so much, appreciate you looking in to it.

    Happy to report in case it can be fixed, but I don't have access to the regular channel myself (academic user).

  • Andrew Beckett

    I'll file a CCR later today.

    Regards,

    Andrew.

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