Re: Requesting datatypes feedback

From: Daryl Stewart (daryl.stewart@tenison.com)
Date: Wed Jun 30 2004 - 07:22:06 PDT

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    Shalom Bresticker wrote:

    >Hi, Daryl.
    >
    >
    >Daryl Stewart wrote:
    >
    >
    >>Shalom Bresticker wrote:
    >>
    >>
    >>
    >>>>In V2K wires are of implicit types "full-strength" or
    >>>>"4-state" depending on their usage.
    >>>>
    >>>>
    >>>I don't know what you mean by 'full-strength'.
    >>>In V2K, all wires are 4-state and all wires have a strength component
    >>>in addition to their value component.
    >>>Even if you disagree with the statement that wires are 4-state because
    >>>you think that 4-state means no strength component, it is still true
    >>>that in V2K, there is only one type of wire.
    >>>
    >>>
    >>>
    >>Rather than strength and value being different components, I've always thought
    >>of 0,1,x and z as an abstraction of strength values, ie all wires have (only)
    >>a strength, which can be modelled as a 2d coordinate on a graph whose axes
    >>both span the 16 strength values; and the wire's value is a projection from
    >>that to {0,1,x,z}. But maybe that's just my take from having written a formal
    >>model of strength resolution in a theorem prover many years ago ;)
    >>
    >>
    >
    >If you look at the last paragraph of 7.9 and the first paragraph of 7.10 in
    >1364-2001, you will see that the strength component of a wire can be ambiguous,
    >i.e., stretch over more than one point.
    >
    >But if you consider the strengths to include value components, then of course
    >you can consider the wire "value" to be a projection or resolution function of
    >all the driver strengths. My point was that in many cases in the language, you
    >refer to the value of the wire without reagrd to its strength. In fact, you have
    >no way today of directly referencing its strength.
    >
    >Regards,
    >Shalom
    >
    >
    >

    Absolutely.

    I didn't mean to start a slightly irrelevant discussion, but a 2d point
    in the 16x16 field defined above cans represent an ambiguous strength.
    Of course, 120 of the 256 points are redundant
    e.gs from section 7.9
     fig 8 is (We0, We1)
     fig 10 is (HiZ1, St1)
     fig 21 is (We0, We0)
    Or maybe you understood this. There's a nice visual method of resolving
    strengths in this graph, but this is not the time or place ;)

    cheers
    Daryl

    >
    >
    >--
    >Shalom Bresticker Shalom.Bresticker @freescale.com
    >Design & Reuse Methodology Tel: +972 9 9522268
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    >
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