Subject: Re: constant function
From: Stefen Boyd (stefen@boyd.com)
Date: Fri Jul 20 2001 - 11:07:41 PDT
At 10:06 AM 7/20/2001 -0700, Stefen Boyd wrote:
>At 10:36 AM 7/20/2001 -0400, Jayaram Bhasker wrote:
>>If you agree with my interpretation of these statements, then one way is
>>to not allow parameter declarations within a constant function (for
>>synthesis).
>>You can still use localparams. Is this reasonable?
>
>Bhasker,
>
>Since localparams can use a parameter in their expression,
>we would have to additionally restrict that for synthesis
>you can't use a parameter to set the value of a localparam.
>At least, you would have to restrict it when the localparam
>is used by a constant function...
>
Bhasker,
I forgot to mention why you don't want to take the
restrictions I mentioned... Since constant functions
were added to enhance the ability to generate
complex logic, you need to be able to use parameter
overrides (which are disallowed for localparam) to
specify the parameters used by the constant function.
If you can't use a parameter, constant functions and
generate aren't as useful.
Keep in mind, we are elaborating and evaluating
constant functions at the same time...
So we want to be able to use parameter override
(hopefully not with defparam) but defparams
might be used, but we can't be sure all their
values have been propagated by the time the
constant function is evaluated... or at least
that's what I remember of the discussion.
Regards,
Stefen
--------------------
Stefen Boyd Boyd Technology, Inc.
stefen@BoydTechInc.com (408)739-BOYD
www.BoydTechInc.com (408)739-1402 (fax)
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