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

There are two aspects of such a model for 'x' (or 'z') in the real domain.
   1) the IEEE language construct definitions (i.e. what happens when
operating
        on real 'x' or 'z' and when converting to/from the logic domain)
   2) the domain/model specific interpretation of an 'x'

I don't know that the domain specific interpretation of 'x' is sufficiently
consistent over all domains that I'd want to embed too much of
that in the LRM. My preference has been to create minimal definition
in the LRM (for core operations only) and to provide additional mechanisms
for the user to define domain specific interpretations for conflicts
or other possible meanings for 'x'.

If we are minimalist in terms of (1) and general in terms of (2) then I
think that we'll have the most opportunity to later refine and special
case domains that are sufficiently general to become part of the IEEE spec.

Gord

On 12/10/2010 12:18 PM, Scott Cranston wrote:
> So this is saying the 'X' in the real domain is "unknown real value". Understood, but how is it used? How is this 'X' treated in the simulation model we are defining?
>
> In the logic (digital) domain, the behavior of the model is defined across all inputs including X, we would need to have something similar in the real domain.
>
> -- Scott
>
>
> -----Original Message-----
> From: Lear, Jim [mailto:Jim.Lear@cirrus.com]
> Sent: Friday, December 10, 2010 2:35 PM
> To: 'Achim Bauer'
> Cc: Scott Cranston; 'sv-dc@eda.org'
> Subject: RE: [sv-dc] 4-state vs 3-D
>
> 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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>>
>>
>>
>>
>
>
>

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Gordon Vreugdenhil                                503-685-0808
Model Technology (Mentor Graphics)                gordonv@model.com
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