//--------------------------------------------------------------------------------------------------
//
// Title       : sort_4_tf.v
// Design      : Homework 1
// Author      : Instructor
// Company     : 
//
//-------------------------------------------------------------------------------------------------
//
// Description : Drives a network that sorts 4 numbers.  A_sort will always be the
// maximum while D_sort will always be the minimum
//
//-------------------------------------------------------------------------------------------------
`timescale 1ns / 1ns


module sort_4_tf ( A,B,C,D,A_sort,B_sort,C_sort,D_sort );

  input [7:0] A_sort, B_sort, C_sort, D_sort ;

  output [7:0] A, B, C, D;
  reg [7:0] 	A, B, C, D;
  
  reg [7:0] A1,B1,C1,D1,A2,B2,C2,D2,B3,C3;
  parameter TESTSIZE = 1000;
  integer     errors, count;

  function [7:0] max;
    input [7:0] X, Y;
    max = X > Y ? X : Y;
  endfunction // max

  function [7:0] min;
    input [7:0] X, Y;
    min = X < Y ? X : Y;
  endfunction // min

  initial begin
    errors = 0;
    for (count = 0; count < TESTSIZE; count = count + 1) begin
      A = $random & 2'hf;
      B = $random & 2'hf;
      C = $random & 2'hf;
      D = $random & 2'hf;
      #20
      A1 = max(A,B);
      B1 = min(A,B);
      C1 = max(C,D);
      D1 = min(C,D);
      A2 = max(A1,C1);
      C2 = min(A1,C1);
      B2 = max(B1,D1);
      D2 = min(B1,D1);
      B3 = max(B2,C2);
      C3 = min(B2,C2);
      if((A_sort !== A2) && (B_sort !== B3) && (C_sort !== C3) && (D_sort !== D2)) begin
	errors = errors + 1;
	$display("Error: Inputs: %d,%d,%d,%d", A, B, C, D);
	$display("      Results: %d,%d,%d,%d", A_sort, B_sort, C_sort, D_sort);
	$stop;
      end
    end // for (count = 0; count < TESTSIZE; count = count + 1)
    $display("%d errors found",errors);
    $finish;
end

endmodule