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

Hi Kev,

looks good, just my analog five cents:

In the analog or real domain "x" or undefined might be interpreted as
undriven (strength=0!) or floating. A floating or high-impedance
(strength=0) node can not really maintain a stable signal, it is prone
to any kind of (unknown) disturbances, the (voltage) value is kind of
undefined. For real values z and x are kind of the same.

So one might even code it in a 2-dimensional way:

Value ( real: -inf -> +inf )
Strength ( real: undriven/undefined = 0, driven = ]0:+inf) )

Which would comply nicely with a sparse struct notation.

Achim

On Wed, 2010-12-08 at 09:13 -0800, Kevin Cameron wrote:
> 4-state refers to the received values "0,1,Z,X", since 0,1 are the range of known good logic values (for a single bit), the same nomenclature doesn't really apply for real values (since there are a lot of valid discrete values).
>
> I'd prefer to call it "3-Dimensional", the dimensions being:
>
> Value (logic: 1,0, real: -inf -> +inf)
> Strength (undriven = z, regardless of type)
> Certainty (uncertain logic = x, uncertain real = NaN)
>
>
> Comments?
>
> Kev.
>
>

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