Source – SV Verification Directory

Super Keyword

The super keyword is useful for accessing the properties and methods of a parent class without needing to declare a parent class handle. It consistently refers to the immediate parent class.

  • By default, SystemVerilog complier calls super.new() function calls automatically from extende class.

  • When the class method require input arguments, the the user has to call super.new{arguments} explicitly.

Note: super.super.{class_member} is not allowed to access multilevel inheritance. Class members are inherited one level up in multiplevel inheritence.

Example Code

// Parent class
class parent_class;
   // class properties or variables
  int a, b, s;

   // task method
  task sum (int a,b);
    this.a = a;
    this.b = b;
    s      = a + b;
  endtask

  function void display();
    $display("Parent Class     => a = %0d , b = %0d, sum s = %0d", a, b ,s);
  endfunction

endclass

// Child Class
class child_class extends parent_class;
  // class properties or variables
  int a, b, m;

  // task method
  task mul (int a,b);
    this.a = a;
    this.b = b;
    m      = a * b;
  endtask

  function void display();
    super.display();           // comment and uncomment to observe the difference
    $display("Child Class      => a = %0d , b = %0d, mul m = %0d", a, b ,m);
  endfunction

endclass

// Multilevel Inheritance
class gran_child_class extends child_class;
  // class properties or variables
  int a, b, d;

  // task method
  task div (int a,b);
    this.a = a;
    this.b = b;
    d      = a / b;
  endtask

  function void display();
    super.display();           // comment and uncomment to observe the difference
    $display("Gran Child Class => a = %0d , b = %0d, div d = %0d", a, b ,d);
  endfunction

endclass


module tb_super_keyword;

  gran_child_class cl_obj;      // declare a class handle of type cl_obj

   initial begin
     cl_obj = new( );      // construct an object
     cl_obj.sum(30,10);    // access a method
     cl_obj.display();
     cl_obj.mul(30,10);    // access a method
     cl_obj.display();
     cl_obj.div(30,10);    // access a method
     cl_obj.display();
   end

endmodule

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