Re: [sv-bc] modport_identifier in an assignment

Dave,

  I don't think there's any confusion about modports resembling
hierarchy.  But you're right to note that the BNF specifies

    interface_identifier
  | interface_identifier . modport_identifier

wherever they can appear in the syntax for port lists.  Thinking
of accesses to a modport or interface as an "expression" misleads
one into believing that there is some fixed type for that expression,
and that modports might appear in other expression contexts.

Can a modport or interface be used in a modport_expression, or in
a modport_simple_ports_declaration?  That might be useful; if one
had a large common modport list, and several minor variations, the
variants would be:

modport mama(a,b,c,d), aunt(mama,import foo), nana(mama, import noo);

The alternative BNF seems messy and less-than-fully general, I'd
rather err on the side of the BNF being too general and the text
needing to restrict it to legal cases.

Perhaps it would help to compile a complete list of the contexts
in which a modport_identifier can be used, and add that list to section 20.4
as a syntax restriction.




Rich, Dave wrote:
> But a modport does not introduce a nested hierarchical scope. We don't
> refer to sb_intf.slave.data or a.slave.data, just sb_intf.data or a.data
> (from that same example)
> 
>  
> 
> Dave
> 
>  
> 
>  
> 
> ________________________________
> 
> From: owner-sv-bc@server.eda.org [mailto:owner-sv-bc@server.eda.org] On
> Behalf Of Brad Pierce
> Sent: Tuesday, April 24, 2007 11:37 PM
> To: sv-bc@server.eda-stds.org; sv-ec@server.eda-stds.org
> Subject: Re: [sv-bc] modport_identifier in an assignment
> 
>  
> 
> Dave,
> 
>  
> 
> A reference to an interface instance is parsed with
> hierarchical_identifier.  For example, 
> 
>  
> 
>               ordered_port_connection  ::= expression ::= primary ::=
> hierarchical_identifier ::= 'sb_intf.slave'
> 
>  
> 
> -- Brad
> 
>  
> 
> ________________________________
> 
> From: owner-sv-bc@eda.org [mailto:owner-sv-bc@eda.org] On Behalf Of
> Rich, Dave
> Sent: Tuesday, April 24, 2007 9:31 AM
> To: sv-bc@eda-stds.org; sv-ec@eda-stds.org
> Subject: [sv-bc] modport_identifier in an assignment
> 
> I've been looking through the BNF and can't find anywhere the BNF allows
> you to put . modport_identifier next to an interface instance on the RHS
> of a assignment. The RHS could be either an actual argument in an
> argument/port list or in the assignment to a virtual interface variable.
> 
>  
> 
> For virtual  interfaces, there's no reason to add this capability other
> than for redundancy, since in order to select a modport, the target must
> have been declared with the specific modport_identifier. There's no BNF
> to support the example in 20.8 (draft1) where there is a
> modport_identifer in the assignment:
> 
>  
> 
> v32_phy = p32.phy;
> 
>  
> 
> For interface port connections, we have this feature where you can
> specify the modport_identifier in the actual port when there is no
> modport declared in the formal port. (See the example in 20.4.3) But I
> can't see any BNF to support this syntax:
> 
>  
> 
> memMod mem(sb_intf.slave); // Connect the modport to the module instance
> 
> cpuMod cpu(sb_intf.master);
> 
>  
> 
>  
> 
>  I'd be happy to remove the feature.
> 
>  
> 
> Dave
> 
>  
> 
>  
> 
> David Rich
> Verification Technologist
> Design Verification & Test Division
> Mentor Graphics Corporation
> dave_rich@mentor.com
> Office:   408 487-7206
> Cell:     510 589-2625
> 
>  
> 
> 



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