adder_higher.v

`include "addbit_module.v"
module adder_higher (
result        , // Output of the adder
carry         , // Carry output of adder
r1            , // first input
r2            , // second input
ci              // carry input
);

// Input Port Declarations       
input    [3:0]   r1         ;
input    [3:0]   r2         ;
input            ci         ;

// Output Port Declarations
output   [3:0]  result      ;
output          carry       ;

// Port Wires
wire     [3:0]    r1        ;
wire     [3:0]    r2        ;
wire              ci        ;
wire     [3:0]    result    ;
wire              carry     ;

// Internal variables
wire              c1        ;
wire              c2        ;
wire              c3        ;

// Code Starts Here
addbit_module u0 (r1[0],r2[0],ci,result[0],c1);
addbit_module u1 (r1[1],r2[1],c1,result[1],c2);
addbit_module u2 (r1[2],r2[2],c2,result[2],c3);
addbit_module u3 (r1[3],r2[3],c3,result[3],carry);

endmodule // End Of Module adder

module tb();

reg [3:0] r1,r2;
reg  ci;
wire [3:0] result;
wire  carry;

// Drive the inputs
initial begin
  r1 = 0;
  r2 = 0;
  ci = 0;
  #10 r1 = 10;
  #10 r2 = 2;
  #10 ci = 1;
  #10 $display("+--------------------------------------------------------+");
  $finish;
end

// Connect the lower module
adder_higher U (result,carry,r1,r2,ci);

// Hier demo here
initial begin
  $display("+--------------------------------------------------------+");
  $display("|  r1  |  r2  |  ci  | u0.sum | u1.sum | u2.sum | u3.sum |");
  $display("+--------------------------------------------------------+");
  $monitor("|  %h   |  %h   |  %h   |    %h    |   %h   |   %h    |   %h    |",
  r1,r2,ci, tb.U.u0.sum, tb.U.u1.sum, tb.U.u2.sum, tb.U.u3.sum); 
end

endmodule