Subject: Re: new attribute (* synthesis, combinational *)
From: Shalom Bresticker (Shalom.Bresticker@motorola.com)
Date: Tue Dec 18 2001 - 00:17:07 PST
Stefen,
You seem to be saying that this attribute will not cause the synthesis tool to synthesize any differently
or in any special way.
Rather, the attribute gives information to the tool that the intention is combinational logic,
so that the tool can yell to tell you that the code does not meet your intention.
Do I understand correctly ?
Shalom
Stefen Boyd wrote:
> At 12:39 PM 12/17/2001 -0800, Raina, Rahul wrote:
> >In the case of an unspecified else, what should the synthesis tool assume?
> >e.g.
> >
> >always @*
> > if (a == 1) x = 0;
> >
> >What should the synthesis tool assume about the a = 0 condition?
>
> Hi Rahul,
>
> The tool shouldn't assume anything. The logic specified
> is not combinational, so the tool should produce an error.
> In your example, since there is no attribute, I would
> expect a latch (although it might do something else since
> you specified a constant value).
>
> The following should produce an error from any tool that
> supports 1364.1:
>
> (* synthesis, combinational *)
> always @*
> if (a)
> q = d;
>
> Regards,
> Stefen
>
> --------------------
> Stefen Boyd Boyd Technology, Inc.
> stefen@BoydTechInc.com (408)739-BOYD
> www.BoydTechInc.com (408)739-1402 (fax)
-- Shalom Bresticker Shalom.Bresticker@motorola.com Principal Staff Engineer 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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