Re: errata/428: PROPOSAL - 2.5.1, value of 16'shc, request for clarification

From: Shalom.Bresticker@motorola.com
Date: Thu Aug 28 2003 - 00:00:01 PDT

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    The following reply was made to PR errata/428; it has been noted by GNATS.

    From: Shalom.Bresticker@motorola.com
    To: brad.pierce@synopsys.com
    Cc: etf-bugs@boyd.com
    Subject: Re: errata/428: PROPOSAL - 2.5.1, value of 16'shc, request for
     clarification
    Date: Thu, 28 Aug 2003 09:54:05 +0300 (IDT)

    > reg signed [84:0] h;
    >
    > h = 16'sb110; // yields {{82{1'b0}}, 3'b110}
     
     Yes, but note that
     
             h = 3'sb110 would yield { {82{1'b1}}, 3'b110}
     
     by NOTE 1 following Example 5, which states that
     
     "Sized negative constant numbers and sized signed constant numbers are
     sign-extended when assigned to a reg data type,
     regardless of whether the reg itself is signed or not."
     
     The 3 notes there should be normative, by the way, whereas NOTES are
     informative only, by IEEE Standard rules.
     
     And if that was not confusing enough, then you also have the following:
     
     8'hx is equivalent to 8'hxx, whereas
     
     a[7:0] = 4'hx gives 8'h0x,
     
     just the opposite of the above rules for sign-bit extension vs.
     left-zero padding.
     
     --
     Shalom Bresticker Shalom.Bresticker@motorola.com
     Design & Reuse Methodology Tel: +972 9 9522268
     Motorola Semiconductor Israel, Ltd. Fax: +972 9 9522890
     POB 2208, Herzlia 46120, ISRAEL Cell: +972 50 441478
     

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