Re: [sv-bc] Query on Virtual (parameterized) interface declaration

From: Surya Pratik Saha <spsaha@cal.interrasystems.com>
Date: Mon Aug 23 2010 - 06:15:59 PDT

Hi,
Further on this topic, I need to understand the meaning of following sentence mentioned in page no 686 of SV 2009 LRM:

The actual values and types of those parameters shall match for an interface and virtual interface to be of the same type and to be assignment compatible (see 6.22.3).

If the types of actual values are of the same type then it is redundant to specify "assignment compatible" as they are anyway assignment compatible. Or LRM wants mean something else. An elaborated example will be very much helpful for that. Is there any Mantis corresponding to that?

Regards
Surya

-------- Original Message  --------
Subject: [sv-bc] Query on Virtual (parameterized) interface declaration
From: Kakoli Bhattacharya <kakoli@cal.interrasystems.com>
To: sv-bc@eda.org
Date: Monday, August 23, 2010 12:57:30 PM

Hello,

Consider the following eg. related to virtual interface (parameterized) declaration

interface intf1 #(parameter shortint size = 3,byte val1 = 8'd4,int val2 = 1) ();

......
modport M1 (... , ....);
endinterface

module top (input var reg [1:0][7:0] in1,output reg [4:0] out1);

intf1 #(7,4,2)I1 (); // ordered parameter assignment used for interface instantiation

virtual interface intf1#(.size(7),.val1(4),.val2(2)).M1 virtual1 = I1; // named parameter assignment
 used for virtual interface declaration

....
endmodule

In the above example ordered parameter assignment is used for interface instatiation, but named
parameter assignment is used for virtual interface declaration, however the parameter values
are same.

Some of the tools are failing at analysis for this.
If named parameter assignment is used for interface instantiation also then it is passing, i.e

intf1 #(.size(7),.val2(2),.val1(4))I1 (); 

If the interface is instantiated as above then passing.

Now in the LRM (Section 25.9) an eg. shows that passing different parameter values is illegal but
it is nowhere mentioned that the parameters have to be assigned in a similar manner (or have I missed
any such clause?)

Tools are also failing for the below given declaration form:

intf1 #() I1 (); // interface instantiated using default values

virtual interface intf1#(.size(3),.val1(4),.val2(1)).M1 virtual1 = I1; // declared using default values
 but it has been explicitly mentioned.

How should the tools behave for such cases?

Regards,
Kakoli

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