Re: [sv-bc] extern modules

Good morning;

I though external declarations were needed for systhesis tools to be
able to work with .* in instantiations. E.g. you read in the external
declaration of the module before it is instantiated with .*.
Unfortunately, this then requires people to know what files to read 
first, or
a suffix to specify them first.




Gordon Vreugdenhil wrote:
>
> Shalom, the restriction only applies when you are
> using .* in the *declaration* of the module in which
> case .* means "pick up the formals that were defined by the
> extern".  The .* use isn't related to an instantiation
> of the module (for which the existence of an extern is
> immaterial anyway).
>
> Extern modules are a bit of an odd feature in SV -- you
> don't need them to instantiate a separately compiled
> module, nor to use .* in an instantiation.  The only
> advantage is for systems that might not want to inhale
> the whole world (synthesis perhaps) or for earlier checking
> of port width/type constraints.  Neither of those aspects
> are directly related to LRM requirements.
>
> Gord
>
> Bresticker, Shalom wrote:
>> Then how do you do separate compilation?
>> And if they're compiled together, what do you need it for?
>>
>> Shalom
>>
>>       _____________________________________________
>>       *From:  * Bresticker, Shalom       *Sent:  * Monday, July 14, 
>> 2008 12:18 PM
>>       *To:    * Bresticker, Shalom
>>       *Subject:       * Re: [sv-bc] extern modules
>>
>>       /From: Gordon Vreugdenhil <//_gordonv_at_....._/
>>       
>> <mailto:gordonv_at_.....?Subject=Re:%20[sv-bc]%20extern%20modules>/>
>>       Date: Thu Jul 10 2008 - 12:37:24 PDT/
>>       Jason,
>>
>>       I agree that with .*, the extern really needs to come first.
>>       Since externs are a way of declaring the "type" of the module
>>       and .* is similar to a dependence on that type, I don't really
>>       see that restriction as being much of a reach either in
>>       practice or as a matter of LRM interpretation.
>>
>>       Gord.
>>
>>
>>       Jason Campbell wrote:
>>        > Hi,
>>        >
>>        >        >
>>        > The LRM doesn't specify if extern can be used subsequent to the
>>       module
>>        > defintion. Is it
>>        >
>>        > correct to assume that this is permitted? Maybe this can be
>>       clarified in
>>        > the LRM.
>>        >
>>        >        >
>>        > If so, this makes implementation of .* in the module port list
>>       quite
>>        > difficult. The reason is
>>        >
>>        > that nets and variables can not be checked for correct usage
>>       until the
>>        > extern is compiled.
>>
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-- 
    Soli Deo Gloria
    Adam Krolnik
    Director of Design Verification
    VeriSilicon Inc.
    Plano TX. 75074
    Co-author "Assertion-Based Design", "Creating Assertion-Based IP"


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