RE: [sv-dc] 4-state vs 3-D

Thanks, Jim and Scott, you convinced me!
Often a logic X is transferred to a mid-rail voltage (between VSS and
VDD) by digital-to-electrical connect modules. If we comply with that, a
3-D real X-value might e.g. look like:
( value = VSS+(VDD-VSS)/2, strength = 1K, state undefined = 1 )

How about Not-a-Number NaN? Might this just be included in the state
like:
state = 0 for specified value
state = 1 for undefined value
state = 2 for NaN

Thanks, Achim

On Fri, 2010-12-10 at 19:34 +0000, Lear, Jim wrote:
> An 'x' value would be useful is when an analog model has an 'x' one of its digital inputs. For example, the value of a DAC output when its enable is 'x' should also be 'x'. It seems like a very useful concept, and it even would be nice to extend into the continuous-time solvers some day.
>
> Kindest Regards,
> Jim Lear
> Cirrus Logic
> (512) 851-4612
> (512) 293-7248 (mobile)
>
> -----Original Message-----
> From: Achim Bauer [mailto:a-bauer@exl-modeling.com]
> Sent: Friday, December 10, 2010 1:24 PM
> To: Lear, Jim
> Cc: 'Scott Cranston'; 'sv-dc@eda.org'
> Subject: RE: [sv-dc] 4-state vs 3-D
>
> I am also not sure how to deal with X for real values,
> because continuous real numbers have no X-gap.
> And I do not see why a "real" X state is necessary for real-to-logic
> conversion or multi-driver resolution of 2-D or 3-D reals.
> Can anybody provide a practical RVM-example where a X-state for real
> values is indispensable ?
>
> -- Achim
>
> On Fri, 2010-12-10 at 17:17 +0000, Lear, Jim wrote:
> > Sure, but the subject states "4-state vs 3-D." Are there two proposals or concepts we're trying to weigh, such as enumerated vs structure?
> >
> > From the electrical domain 'Z' is reasonably straightforward. The 'X' is a new concept for that side, but the NaN is quite similar. The subtleties are escaping me.
> >
> > Kindest Regards,
> > Jim Lear
> > Cirrus Logic
> > (512) 851-4612
> > (512) 293-7248 (mobile)
> >
> > -----Original Message-----
> > From: Scott Cranston [mailto:cranston@cadence.com]
> > Sent: Friday, December 10, 2010 10:28 AM
> > To: Lear, Jim; 'sv-dc@eda.org'
> > Subject: RE: [sv-dc] 4-state vs 3-D
> >
> > I think we're trying to decide what is being modeled in real modeling and (a subdecision) what X means in that model.
> >
> > -- Scott
> >
> >
> > -----Original Message-----
> > From: owner-sv-dc@eda.org [mailto:owner-sv-dc@eda.org] On Behalf Of Lear, Jim
> > Sent: Friday, December 10, 2010 9:25 AM
> > To: 'sv-dc@eda.org'
> > Subject: RE: [sv-dc] 4-state vs 3-D
> >
> > I'm not sure how important this is, but in the AMS world with boundary models (connect rules), an 'X' can also represent a Voltage that is between the zero- and one-threshold; the meta-stability region. This arises in the conversion from a known Voltage to a logic value.
> >
> > I'm not sure exactly what we're trying to solve. Are we trying to decide between a "four state" and a "3-D" implementation? It's not clear what exactly is meant between the two. Would someone be kind enough to clarify?
> >
> > Kindest Regards,
> > Jim Lear
> > Cirrus Logic
> > (512) 851-4612
> > (512) 293-7248 (mobile)
> >
> >
> >
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