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CDF parameters constantly revert back to prior settings

srftech

So I routinely create libraries where we release it as an IP, with only layout, symbol, spectre and auCdl views for the customer to access.

The spectre and auCdl views have CDF parameters such as model, termorder, etc pointing to external files/netlist the customer can include to run simulations or export CDL of larger blocks,  integrating cells frrom our library. 

Periodically I run into a problem where:

 1. I have create a cell, many times copying it from another cell that is similar, and making a few custom edits.  I usually have to edit the CDF parameters to match as well, primarily fixing termorder and the model name parameter so the specre/auCdl views points to the correct model in the external include files.

2. BUT...Every time I reload virtuoso, all of the cdf parameters of this one (or possibly multiple cells) revert back to original settings or older CDF parameters.  As if they were never changed.

No matter how many times I change the parameters, apply and save, they are only good as long as I do not close that virtuoso session, but once I close it and then reopen it, it is as if I never changed them in the first place. 

I have gone into the database, I do not see any obvious files like lock files blocking the saving of the parameters, but, I am still at a loss.

Any suggestions would be appreciated.

 Regards

  • Almost certainly you haven’t set the CDF type to “Base” but instead are editing the Effective or User CDF (Effective is the default). Effective and User only change the CDF in memory; you need to pick Base if you want to save the changes to disk.

    Regards,

    Andrew

  • Thank you Andrew, and you are correct about what I was editing.
    I had no idea the difference between them actually. It was once explained to me that base would change the PDK defaults for multiple cells and that I was supposed to avoid it. Your explanation makes a lot more sense. If I have further issues I will let you know but this will solve a long annoying problem I have dealt with over the years.

    Incidentally, for my own education, why have Effective and User then? What is the advantage and what is the difference between Effective and User?

  • User is just the in-memory parts and so quite hard to visualise. Effective is the overlay of the user CDF on top of the base so it shows you what it resolves to in memory; any changes you make to the effective are actually changing the user CDF.

    User/Effective are useful when you want to either make a change when you don’t have permission to save, or don’t want to permanently modify the CDF.

    Andrew

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