Re: errata/9: Modified proposal wording - truncation

From: Shalom.Bresticker@motorola.com
Date: Wed Apr 09 2003 - 03:30:02 PDT

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    The following reply was made to PR errata/9; it has been noted by GNATS.

    From: Shalom.Bresticker@motorola.com
    To: "Clifford E. Cummings" <cliffc@sunburst-design.com>
    Cc: etf-bugs@boyd.com
    Subject: Re: errata/9: Modified proposal wording - truncation
    Date: Wed, 9 Apr 2003 13:21:48 +0300 (IDT)

     In last sentence, "Truncating the sign bit of a signed expression, may change
     the sign of the result." there should be no comma after the word "expression".
     
     Shalom
     
     
     On Mon, 7 Apr 2003, Clifford E. Cummings wrote:
     
    > Based on today's discussion, the ETF-9 proposal should be changed as shown
    > below. Still outstanding is the "assignment" wording in the first paragraph
    > and where this addition should be placed in the LRM. The attached PDF file
    > is formatted and colorized.
    >
    > Blue - wording changes to the proposal made in today's meeting.
    > Red - still seeking better wording.
    >
    > 6.3 Assignments of different sizes
    > (perhaps should be a new section 4.6 instead of 6.3)
    >
    > If the width of the right-hand side (RHS) expression is larger than the
    > width of the left-hand side (LHS) in a continuous assignment, procedural
    > assignment or continuous procedural assignment, the MSBs of the RHS
    > expression will always be discarded to match the size of the LHS. Compliant
    > Verilog simulators are not required to warn or report any errors related to
    > assignment size-mismatch or truncation. Truncating the sign bit of a signed
    > expression, may change the sign of the result.
    >
    > (change wording to, "an assignment" ??)
    >
    > Example:
    > reg [5:0] a; reg signed [4:0] b;
    >
    > initial begin
    > a = 8'hff; // After the assignment, a = 6'h3f
    > b = 8'hff; // After the assignment, b = 5'h1f
    > end
    >
    > Example:
    > reg [0:5] a; reg signed [0:4] b, c; initial begin a =
    > 8'sh8f; // After the assignment, a = 6'h0f b = 8'sh8f; // After the
    > assignment, b = 5'h0f
    > c = -113; // After the assignment, c = 15
    > end
    > // 1000_1111 = (-'h71 = -113) truncates to ('h0F = 15)
    >
    > Example:
    > reg [7:0] a; reg signed [7:0] b; reg signed [5:0] c,
    > d; initial begin a = 8'hff; c = a; // After the assignment, c =
    > 6'h3f b = -113;
    > d = b; // After the assignment, d = 6'h0f
    > end
     

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