RE: [SI-LIST] : Ibis models

Chris Rokusek (crokusek@viewlogic.com)
Tue, 28 Sep 1999 09:19:27 -0700

Jim, Abe,

> Abe, are you sure of the XTK monotonicity requirement? I seem to recall
> that the earlier versions of XTK required monotonicity almost
> everywhere,
> but the newer ones relaxed many of those requirements. Quad stopped
> supplying hard-copy manuals with new versions of software sometime last
> year, so any official Quad manuals you might have are probably obsolete.
> The online docs are still being updated with each release.
>
> Anybody from Quad/Viewlogic High Speed Design care to comment?

Recent versions of XTK don't mind if individual curves are non-monotonic
when the keyword "NON_MON" is present (see docs). When using this keyword
its crucial is that each logic STATE (sum of appropriate I-V curves) is
monotonic (this is verified and fixed if necessary during IBIS translation).

Chris

> -----Original Message-----
> From: owner-si-list@silab.eng.sun.com
> [mailto:owner-si-list@silab.eng.sun.com]On Behalf Of Laurence Michaels
> Sent: Tuesday, September 28, 1999 7:47 AM
> To: si-list@silab.eng.sun.com
> Subject: Re: [SI-LIST] : Ibis models
>
>
> Abe Riazi wrote:
> >
> > Jim Freeman Wrote:
> >
> > >> These ibis models as so generated are taken by both the
> > >>ibis2xtk utility and the ibis2signoise utility and generate acceptable
> > >>models to both of these simulators. In the Cadence info for
> the 2.1 GUI
> > >>that they provide, it is stated that most simulators perform smoothing
> > >>functions on the IBIS models before they use them.
> > >
> > >
> > Hi Jim:
> >
> > Based on experience with IBIS and XTK models, I agree with above
> > statements. The I-V sections of an IBIS model include:
> >
> > pullup
> > pulldown
> > GND_clamp
> > POWER_ clamp
> >
> > The corresponding I-V curves of XTK models consist of:
> >
> > HIGH
> > LOW
> > SHUNT
> > SHUNTP
> >
> > The IBIS format does not require monotonicity for the I-V tables.
> > However, the XTK simulator demands that the I-V curves of the Quad
> > models to be monotonic. When translating an IBIS model having
> > non-monotonic I-V data, IBIS2XTK shifts the currents between the LOW/
> > HIGH state curves and SHUNT/ SHUNTP curves (or deletes some points if
> > necessary) towards generating monotonic curves.
> >
> > While I have seen numerous IBIS models having non-monotonic I-V data,
> > I have not noticed any XTK models with non-monotonic I-V curves.
>
> Abe, are you sure of the XTK monotonicity requirement? I seem to recall
> that the earlier versions of XTK required monotonicity almost
> everywhere,
> but the newer ones relaxed many of those requirements. Quad stopped
> supplying hard-copy manuals with new versions of software sometime last
> year, so any official Quad manuals you might have are probably obsolete.
> The online docs are still being updated with each release.
>
> Anybody from Quad/Viewlogic High Speed Design care to comment?
>
> Possibly useful SI information: Fasthenry from MIT seems to be very
> nice,
> and much cheaper (free?) than many commercial 3D inductance calculators.
> I'm still checking it out myself, and it seems fairly stable so far.
>
> Regards,
> --
> Laurence Michaels
>
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