errata/228: 4.2.1, indexed part-select with width-expression of -5

From: Brad Pierce (Brad.Pierce@synopsys.com)
Date: Mon Dec 23 2002 - 19:29:16 PST

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    >Number: 228
    >Category: errata
    >Originator: "Brad Pierce" <Brad.Pierce@synopsys.com>
    >Environment:
    >Description:

    Which constant expressions are legal as width expressions
    in an indexed part-select? The width is said to indicate
    the number of bits selected. So we shouldn't be able to
    select 0 bits, e.g.,

      big_vect[15 +: 0]

    But what about

      big_vect[15 +: -5] ?

    Is -5 cast to signed or should this produce an error?
    What about 5.0?

    What does this mean? --

      "The last one shows an indexable nature."

    The initial block is a strange way to "show the identity
    between the two part select constructs".

    The example isn't numbered.

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