Re: errata/318: Table 30, 9.3.2,procedural assign to nonconstant part select and force of nonconstantbit-select

From: Dennis Marsa (drm@xilinx.com)
Date: Tue Apr 01 2003 - 12:10:02 PST

  • Next message: Shalom.Bresticker@motorola.com: "Re: errata/318: Table 30, 9.3.2, procedural assign to nonconstant part select and force of nonconstant bit-select"

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    The following reply was made to PR errata/318; it has been noted by GNATS.

    From: Dennis Marsa <drm@xilinx.com>
    To: Brad Pierce <Brad.Pierce@synopsys.com>
    Cc: etf-bugs@boyd.com
    Subject: Re: errata/318: Table 30, 9.3.2,procedural assign to nonconstant part
     select and force of nonconstantbit-select
    Date: Tue, 01 Apr 2003 13:07:26 -0700

     Brad Pierce wrote:
    >
    > Precedence: bulk
    >
    > >Number: 318
    > >Category: errata
    > >Originator: "Brad Pierce" <Brad.Pierce@synopsys.com>
    > >Environment:
    > >Description:
    >
    > In Table 30, why can the left-hand side of a procedural
    > assignment use a nonconstant bit-select or a nonconstant
    > indexed part-select, but only a constant part-select?
    >
    > In 9.3.2 why can the left-hand side of a force be a nonconstant
    > part-select, but only a constant bit-select?
    >
    > -- Brad
     
     A part-select is by definition constant. That is, the msb and
     lsb expressions are required to be constant expressions in all
     contexts. See BNF rule range_expression in A.8.3.
     
     In Table 30, where the term "constant part-select" is used,
     the "constant" is redundant.
     
     In 9.3.2, where just the term "part-select" is used, the
     fact that it is constant is implicit in the definition of
     a part-select. Note the word "nonconstant" is not used in
     9.3.2.
     
     For bit-selects and indexed part-selects, it makes sense to
     distinguish between constant and non-constant forms. But
     not for part-selects, they are always constant.
     
     Dennis

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