How does VCS support parameterized virtual interface?

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本文通过具体示例深入探讨了虚拟接口在参数化中的应用，包括使用虚拟接口作为参数化的类型参数以及如何在参数化类中利用虚拟接口。详细解释了合法与非法的赋值操作，并展示了如何在不同参数化模块之间进行赋值。

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Answer:


1. Following is an example of using a parameterized virtual interface with 
   legal or illegal assignments which works as mentioned(in comments/LRM) 
   in VCS:


-------------------------------------------------------------------------------


            
        interface PBus #(WIDTH=8);  // A parameterized bus interface
         logic req, grant;
         logic [WIDTH-1:0] addr, data;


         modport phy(input addr, ref data);
        endinterface


        module top;
         PBus #(16) p16();
         PBus #(32) p32();


         virtual PBus V8;
         virtual PBus #(35) V35;
         virtual PBus #(16) v16;
         virtual PBus #(16).phy v16_phy;
         virtual PBus #(32) v32;
         virtual PBus #(32).phy v32_phy;


         initial begin
        //following is legal as parameter values match
          v16 = p16; 


        //following is legal as parameter values match 
          v32 = p32; 


        //following is illegal as parameter values do not match
          //v16 = p32; 


        //following is illegal as parameter values do not match
          //v16 = v32; 


        //following is a legal assignment from no selected modport 
        //to selected modport
          v16_phy = v16; 


        //following is an illegal assignment from selected modport 
        //to no selected modport
          //v16 = v16_phy; 


        //following is a legal assignment from no selected modport 
        //to selected modport
          v32_phy = p32; 
        //to no selected modport
          //v32 = p32.phy;  


         end
        endmodule


--------------------------------------------------------------------------------




2. Following is an example of virtual interface being used as a type parameter 
   of a parameterized class, which is supported by VCS:


--------------------------------------------------------------------------------




        interface PBus #(WIDTH=8);  // A parameterized bus interface
         logic req, grant;
         logic [WIDTH-1:0] addr, data;


         modport phy(input addr, ref data);
        endinterface


        module top;
         PBus #(16) p16();
         PBus #(32) p32();
         prog pg(p16);
        endmodule


        program prog(interface I);
        //Parameter can be overridden at type declaration if required
         class cls#(type Tp = virtual PBus #(16));
          Tp vpbus;


          function new;
        // need to assign a proper interface instance depending on the 
        //parameter value being overridden
            vpbus = I;
          endfunction
         endclass
        endprogram

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