From: Shalom Bresticker (shalom@msil.sps.mot.com)
Date: Sun Mar 08 1998 - 01:05:44 PST
> From: "Thomas Fitzpatrick" <tfitz@cadence.com>
> Date: Wed, 4 Mar 1998 10:44:10 -0500
> Subject: BTF B19 - Signed Arithmetic Proposal (Updated)
<p>BAD MSG:
>
6. Part-select results are unsigned, regardless of the operands.
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I have not followed the proposal very carefully,
but I see a potential problem in this particular sentence.
It is a common practice when using vectors to write it as a part-select of
the entire vector, in order to emphasize the width of the vector. This
reduces the likelihood of making a mistake.
While doing so in some cases reduces simulator performance,
it has never affected the functionality of the code, e.g.,
wire [5:0] a,b,c ;
a[5:0] = b[5:0] & c[5:0] ;
and
wire [5:0] a,b,c ;
a = b & c ;
were always the same.
This sentence of the proposal would eliminate that possibilty for signed operands.
On the other hand, I agree that it is logical that part-selects should be unsigned.
I don't have a better idea, but maybe someone else does ?
Sincerely,
Shalom Bresticker
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Shalom Bresticker email: shalom@msil.sps.mot.com
Motorola Semiconductor Israel, Ltd. Tel #: +972 9 9522268
P.O.B. 2208, Herzlia 46120, ISRAEL Fax #: +972 9 9522444
http://www.motorola-semi.co.il/
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