RE: array parameters overrides

Note that in SV, all integer types are type-equivalent, but integer and
real are not.

Shalom

> -----Original Message-----
> From: owner-verilog-ams@server.eda.org [mailto:owner-verilog-
> ams@server.eda.org] On Behalf Of Geoffrey.Coram
> Sent: Thursday, April 19, 2007 2:58 PM
> Cc: verilog-ams
> Subject: Re: array parameters overrides
> 
> Marq -
> The second bullet, as presently in the LRM, doesn't say anything
> about the default value provided.  In some cases, the LRM allows
> the default value to be illegal:
>   parameter real pos_num = -1 from [0: inf);
> is syntatically legal, and effectively requires the user to
> supply a value.  I suppose the same sort of thing might be
> possible for arrays, that the default array would be the
> wrong size, so you'd be required to specify an array when
> you instantiate the module.
> 
> Actually, we have something of a problem with this:
>        parameter integer active[0:1] = { "yes", "no" };
> because 1364 Verilog considers a string literal like "yes"
> to be an integer type.  In 3.2.1, I put in language to prevent
> coercion from string to real or integer, but it was later
> pointed out that this is not consistent with 1364.
> 
> -Geoffrey
> 
> 
> 
> Marq Kole wrote:
> >
> > Geoffrey,
> >
> > I was trying to work from the original text and apparently got
> myself in a bigger mess :-)
> >
> > I agree with your proposal although I have the impression that the
> LRM makes a distinction between assignment which is done when
> providing a default value and overriding the default values by either
> a defparam, instance parameter override by position or instance
> parameter override by name. Your first proposed bullet (An array
> assigned ...) should probably also mention the assignment of the
> default value for an array parameter.
> >
> > The equivalent type was put in as in case of integer vs real arrays
> coercion can be used, in case of a string array (do have those?) it
> can't be done. Or put in other words, each array element is assigned a
> value as though it were a scalar initialized by a scalar constant.
> >
> > It allows:
> >
> >         parameter real pwl[0:3] = {0, 0, 1, 1}; // initialize real
> array with integer values
> >
> > It disallows:
> >
> >         parameter integer active[0:1] = { "yes", "no" };
> >
> > Cheers,
> > Marq
> >
> > ------ original message follows ----
> >
> > Marq -
> > The existing bullet says:
> > * An array assigned to an instance of a module shall be of the exact
> size
> > of the array bounds of that instance
> >
> > This seems to say what you needed it to say for the examples
> > you sent earlier (trying to override the array parameter
> > with shorter or longer arrays).  I don't see how your
> > proposed text helps, unless you are saying that "assigned
> > to an instance of a module" isn't precise, since it doesn't
> > make clear that "assigning to an instance" is really meant
> > to be overriding the default value.
> >
> > "array bounds of that instance" is a little odd, also, since
> > the "instance" doesn't have array bounds, only the parameter.
> >
> > I will also note that "equivalent type" isn't necessary; one could
> > have coercion (real to integer or vice-versa).  Perhaps, though,
> > we should say something about strings.
> >
> > How about:
> > * An array assigned to an instance of a module to override the
> > default value of an array parameter shall be of the exact size
> > of the parameter array, as determined by its declaration.
> >
> > * Since array range in the parameter array declaration may
> > depend on previously-declared parameters, the array size
> > can be changed by overriding the appropriate parameters.
> > If the array size is changed, the parameter array shall be
> > assigned an array of the new size from the same module
> > as the parameter assignment that changed the parameter
> > array size.
> >
> > -Geoffrey
> >
> > Marq Kole wrote:
> > >
> > > All,
> > >
> > > I propose the following text to replace the second bullet in the
> list in section 3.2.4 (Parameter Arrays):
> > >
> > >    * An array assigned to an instance of a module or overriding
> the default value of an array parameter in an instance of a module
> shall be of the exact size as defined by the array bounds of that
> instance parameter. Assigning to an array requires also that each
> element to be of an equivalent type.
> > >
> > > Cheers,
> > > Marq
> 
> --
> This message has been scanned for viruses and
> dangerous content by MailScanner, and is
> believed to be clean.

-- 
This message has been scanned for viruses and
dangerous content by MailScanner, and is
believed to be clean.