Re: Enhancement: Dynamic Values on attributes.

From: Krishna Garlapati (krishna@synplicity.com)
Date: Tue Nov 04 2003 - 14:17:11 PST

  • Next message: Steven Sharp: "Re: Enhancement: Dynamic Values on attributes."

    I agree with you that $strcat can does both concatenation and conversion
    and
    can be split into 2 functions. We can start with $itos and $itoa and extend
    the functionality to include $itosb, $itosh, itoso and anything else
    to make it
    fully specified.

    But I still do think that Verilog should provide a function that
    performs concatenation
    and conversion instead of asking the user to write one using these. This
    functionality
    is too often used, and is much better if Verilog provides a solution
    natively.

    Using the $itos approach, $strcat can be represented as:

    (* some_name = $strcat("Hello", "World", $itos(i), $itosb(15) *) //
    assume i is 1
    resulting in some_name = "HelloWorld14'b1111"

    There are a couple of issues here though. Will the proposed $itosb write
    the output
    as 4'b1111 or 1111 or {7{0000}, 1111} ?? You can see that the size of
    the output string
    can vary greatly depending on the approach. A possible solution is to
    explicitly specify in the
    LRM that the size of the output string of $itos will always be the
    least possible size size.

    Extending these functions to variables is generally a good idea. The
    sizing issues that popup can
    again be addressed pretty easilt if the LRM can impose restrictions on
    the maximum size of string buffers
    that can be generated. (for unknown sizes only at compile time)

    I found out that the backend tools are very picky if we any chars are
    padded to the output string.
    I think we should concatenate the resutant string without any spaces or
    delimeters. If the user wants
    to add leading spaces (or any delimeters) it can always be done by
    adding a NULL string within the
    parameters to $stract. 

    -- 
- Krishna Garlapati, Synplicity Inc. (408)215-6152

    This archive was generated by hypermail 2.1.4 : Tue Nov 04 2003 - 14:10:29 PST and
    sponsored by Boyd Technology, Inc.