Re: errata/483: 4.2: Bit/part-selects of parameters

From: Steven Sharp (sharp@cadence.com)
Date: Mon Sep 22 2003 - 14:40:00 PDT

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    The following reply was made to PR errata/483; it has been noted by GNATS.

    From: Steven Sharp <sharp@cadence.com>
    To: etf-bugs@boyd.com, Shalom.Bresticker@motorola.com
    Cc:
    Subject: Re: errata/483: 4.2: Bit/part-selects of parameters
    Date: Mon, 22 Sep 2003 18:29:54 -0400 (EDT)

    > This is sort of a side-question, but what is the type of a parameter
    > without a type specification? The LRM does not say explicitly (3.11.1).
    > I think it should say that it is implicitly declared as a "reg" type,
    > like functions.
     
     I'm not sure what you mean here. "reg" isn't really a data type.
     A variable declared with the keyword "reg" has a datatype of a scalar or
     vector of 4-state bits. But that is not specific to regs, since there are
     nets and parameters of that type. A parameter without a type specification
     takes on the type of the value it is set to, which is either real or vector
     (which can be signed or unsigned).
     
     The other aspect of a reg, besides its data type, is that it is a variable.
     A parameter is not a variable, and does not have the same read/write
     semantics as a variable. Perhaps you meant that it is not a net, which is
     true. It is a parameter, which has semantics distinct from variables and
     nets. Unlike nets, it does not have strength or delay or drivers. Unlike
     variables, it cannot be written to in procedural code.
     
     Steven Sharp
     sharp@cadence.com
     

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