Re: Paramset Proposal

Kevin Cameron wrote:
> That would be the wrong way round (IMO) since that puts the potentially
> best match last.

It's last within the file, but at least the simulator doesn't have
to go read in lots of other files that might have been specified as
alternate libraries. (In your way of doing things, the order doesn't
matter, since the simulator has to check everything anyway, so why
would you want the best match first?)

> Your citing a case were the choice is probably immaterial, however, if
> there was
> a mistake in the model paramset definition (i.e. incorrectly overlapping
> cases) I
> would like to get a warning (at least). I prefer it to be defined as an
> error in the LRM
> and allow vendors to provide overrides.

I'm citing a case where the selection CANNOT be done except by
first-match (or flipping a coin). It shouldn't be the simulator's
job to check for errors in the library of paramsets -- checking
for each instance it looks up, for each circuit, for each simulation.

If the cases were overlapping (not just abutting), you say you'd want
at least a warning, but the overlap might actually be a floating-point
roundoff problem; I've seen model cards with something like
lmin = 0.35u + dl_stat (where dl_stat is chosen appropriate to the
fast/slow/nom corner). So, now you have to introduce rules that say,
well, OK, they can overlap, but not more than a tolerance ...
It quickly gets out of hand.

> I would prefer to leave that information out of the module and put it in
> the paramset
> itself - e.g. add a parameter to the set indicating its detail level
> and switch on it
> procedurally.

The detail_level parameter is a paramset-parameter, so the
information is not in the module. You can then use defparam to
set the detail_level for particular instances.

>>
> I think this needs to be defined a lot better than it is currently, and
> source order as
> part of the algorithm is a complete "no-no".

Source order as part of the algorithm is unavoidable, as I proved
in my example with bins.

-Geoffrey
Received on Mon May 17 11:49:57 2004