text: // Copyright 2009 Altera Corporation. All rights reserved.  
  // Altera products are protected under numerous U.S. and foreign patents, 
  // maskwork rights, copyrights and other intellectual property laws.  
  //
  // This reference design file, and your use thereof, is subject to and governed
  // by the terms and conditions of the applicable Altera Reference Design 
  // License Agreement (either as signed by you or found at www.altera.com).  By
  // using this reference design file, you indicate your acceptance of such terms
  // and conditions between you and Altera Corporation.  In the event that you do
  // not agree with such terms and conditions, you may not use the reference 
  // design file and please promptly destroy any copies you have made.
  //
  // This reference design file is being provided on an "as-is" basis and as an 
  // accommodation and therefore all warranties, representations or guarantees of 
  // any kind (whether express, implied or statutory) including, without 
  // limitation, warranties of merchantability, non-infringement, or fitness for
  // a particular purpose, are specifically disclaimed.  By making this reference
  // design file available, Altera expressly does not recommend, suggest or 
  // require that this reference design file be used in combination with any 
  // other product not provided by Altera.
  /////////////////////////////////////////////////////////////////////////////
  
  //
  // 32 bit CRC of 32 data bits (forward - LSB first)
  // polynomial : 00a00805 
  //    x^23 + x^21 + x^11 + x^2 + x^0
  //
  //        CCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCC DDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDD 
  //        00000000001111111111222222222233 00000000001111111111222222222233 
  //        01234567890123456789012345678901 01234567890123456789012345678901 
  // C00  = #........#.#......#..##....#.### ###.#....##..#......#.#........# 
  // C01  = .#........#.#......#..##....#.## ##.#....##..#......#.#........#. 
  // C02  = #.#......#...#....#.#####..#..#. .#..#..#####.#....#...#......#.# 
  // C03  = .#.#......#...#....#.#####..#..# #..#..#####.#....#...#......#.#. 
  // C04  = ..#.#......#...#....#.#####..#.. ..#..#####.#....#...#......#.#.. 
  // C05  = ...#.#......#...#....#.#####..#. .#..#####.#....#...#......#.#... 
  // C06  = ....#.#......#...#....#.#####..# #..#####.#....#...#......#.#.... 
  // C07  = .....#.#......#...#....#.#####.. ..#####.#....#...#......#.#..... 
  // C08  = ......#.#......#...#....#.#####. .#####.#....#...#......#.#...... 
  // C09  = .......#.#......#...#....#.##### #####.#....#...#......#.#....... 
  // C10  = ........#.#......#...#....#.#### ####.#....#...#......#.#........ 
  // C11  = #....................#.......... ..........#....................# 
  // C12  = .#....................#......... .........#....................#. 
  // C13  = ..#....................#........ ........#....................#.. 
  // C14  = ...#....................#....... .......#....................#... 
  // C15  = ....#....................#...... ......#....................#.... 
  // C16  = .....#....................#..... .....#....................#..... 
  // C17  = ......#....................#.... ....#....................#...... 
  // C18  = .......#....................#... ...#....................#....... 
  // C19  = ........#....................#.. ..#....................#........ 
  // C20  = .........#....................#. .#....................#......... 
  // C21  = #........###......#..##....#.##. .##.#....##..#......###........# 
  // C22  = .#........###......#..##....#.## ##.#....##..#......###........#. 
  // C23  = #.#......#..##....#.#####..#..#. .#..#..#####.#....##..#......#.# 
  // C24  = .#.#......#..##....#.#####..#..# #..#..#####.#....##..#......#.#. 
  // C25  = ..#.#......#..##....#.#####..#.. ..#..#####.#....##..#......#.#.. 
  // C26  = ...#.#......#..##....#.#####..#. .#..#####.#....##..#......#.#... 
  // C27  = ....#.#......#..##....#.#####..# #..#####.#....##..#......#.#.... 
  // C28  = .....#.#......#..##....#.#####.. ..#####.#....##..#......#.#..... 
  // C29  = ......#.#......#..##....#.#####. .#####.#....##..#......#.#...... 
  // C30  = .......#.#......#..##....#.##### #####.#....##..#......#.#....... 
  // C31  = ........#.#......#..##....#.#### ####.#....##..#......#.#........ 
  //
  // Number of XORs used is 32
  // Maximum XOR input count is 26
  //   Best possible depth in 4 LUTs = 3
  //   Best possible depth in 5 LUTs = 3
  //   Best possible depth in 6 LUTs = 2
  // Total XOR inputs 520
  //
  
  module fec_parity (
      input [31:0] c,
      input [31:0] d,
      output [31:0] co
  );
  
  assign co[0] =
      c[0] ^ c[9] ^ c[11] ^ c[18] ^ c[21] ^ c[22] ^ 
      c[27] ^ c[29] ^ c[30] ^ c[31] ^ d[0] ^ d[1] ^ d[2] ^ 
      d[4] ^ d[9] ^ d[10] ^ d[13] ^ d[20] ^ d[22] ^ d[31];
  
  assign co[1] =
      c[1] ^ c[10] ^ c[12] ^ c[19] ^ c[22] ^ c[23] ^ 
      c[28] ^ c[30] ^ c[31] ^ d[0] ^ d[1] ^ d[3] ^ d[8] ^ 
      d[9] ^ d[12] ^ d[19] ^ d[21] ^ d[30];
  
  assign co[2] =
      c[0] ^ c[2] ^ c[9] ^ c[13] ^ c[18] ^ c[20] ^ 
      c[21] ^ c[22] ^ c[23] ^ c[24] ^ c[27] ^ c[30] ^ d[1] ^ 
      d[4] ^ d[7] ^ d[8] ^ d[9] ^ d[10] ^ d[11] ^ d[13] ^ 
      d[18] ^ d[22] ^ d[29] ^ d[31];
  
  assign co[3] =
      c[1] ^ c[3] ^ c[10] ^ c[14] ^ c[19] ^ c[21] ^ 
      c[22] ^ c[23] ^ c[24] ^ c[25] ^ c[28] ^ c[31] ^ d[0] ^ 
      d[3] ^ d[6] ^ d[7] ^ d[8] ^ d[9] ^ d[10] ^ d[12] ^ 
      d[17] ^ d[21] ^ d[28] ^ d[30];
  
  assign co[4] =
      c[2] ^ c[4] ^ c[11] ^ c[15] ^ c[20] ^ c[22] ^ 
      c[23] ^ c[24] ^ c[25] ^ c[26] ^ c[29] ^ d[2] ^ d[5] ^ 
      d[6] ^ d[7] ^ d[8] ^ d[9] ^ d[11] ^ d[16] ^ d[20] ^ 
      d[27] ^ d[29];
  
  assign co[5] =
      c[3] ^ c[5] ^ c[12] ^ c[16] ^ c[21] ^ c[23] ^ 
      c[24] ^ c[25] ^ c[26] ^ c[27] ^ c[30] ^ d[1] ^ d[4] ^ 
      d[5] ^ d[6] ^ d[7] ^ d[8] ^ d[10] ^ d[15] ^ d[19] ^ 
      d[26] ^ d[28];
  
  assign co[6] =
      c[4] ^ c[6] ^ c[13] ^ c[17] ^ c[22] ^ c[24] ^ 
      c[25] ^ c[26] ^ c[27] ^ c[28] ^ c[31] ^ d[0] ^ d[3] ^ 
      d[4] ^ d[5] ^ d[6] ^ d[7] ^ d[9] ^ d[14] ^ d[18] ^ 
      d[25] ^ d[27];
  
  assign co[7] =
      c[5] ^ c[7] ^ c[14] ^ c[18] ^ c[23] ^ c[25] ^ 
      c[26] ^ c[27] ^ c[28] ^ c[29] ^ d[2] ^ d[3] ^ d[4] ^ 
      d[5] ^ d[6] ^ d[8] ^ d[13] ^ d[17] ^ d[24] ^ d[26];
  
  assign co[8] =
      c[6] ^ c[8] ^ c[15] ^ c[19] ^ c[24] ^ c[26] ^ 
      c[27] ^ c[28] ^ c[29] ^ c[30] ^ d[1] ^ d[2] ^ d[3] ^ 
      d[4] ^ d[5] ^ d[7] ^ d[12] ^ d[16] ^ d[23] ^ d[25];
  
  assign co[9] =
      c[7] ^ c[9] ^ c[16] ^ c[20] ^ c[25] ^ c[27] ^ 
      c[28] ^ c[29] ^ c[30] ^ c[31] ^ d[0] ^ d[1] ^ d[2] ^ 
      d[3] ^ d[4] ^ d[6] ^ d[11] ^ d[15] ^ d[22] ^ d[24];
  
  assign co[10] =
      c[8] ^ c[10] ^ c[17] ^ c[21] ^ c[26] ^ c[28] ^ 
      c[29] ^ c[30] ^ c[31] ^ d[0] ^ d[1] ^ d[2] ^ d[3] ^ 
      d[5] ^ d[10] ^ d[14] ^ d[21] ^ d[23];
  
  assign co[11] =
      c[0] ^ c[21] ^ d[10] ^ d[31];
  
  assign co[12] =
      c[1] ^ c[22] ^ d[9] ^ d[30];
  
  assign co[13] =
      c[2] ^ c[23] ^ d[8] ^ d[29];
  
  assign co[14] =
      c[3] ^ c[24] ^ d[7] ^ d[28];
  
  assign co[15] =
      c[4] ^ c[25] ^ d[6] ^ d[27];
  
  assign co[16] =
      c[5] ^ c[26] ^ d[5] ^ d[26];
  
  assign co[17] =
      c[6] ^ c[27] ^ d[4] ^ d[25];
  
  assign co[18] =
      c[7] ^ c[28] ^ d[3] ^ d[24];
  
  assign co[19] =
      c[8] ^ c[29] ^ d[2] ^ d[23];
  
  assign co[20] =
      c[9] ^ c[30] ^ d[1] ^ d[22];
  
  assign co[21] =
      c[0] ^ c[9] ^ c[10] ^ c[11] ^ c[18] ^ c[21] ^ 
      c[22] ^ c[27] ^ c[29] ^ c[30] ^ d[1] ^ d[2] ^ d[4] ^ 
      d[9] ^ d[10] ^ d[13] ^ d[20] ^ d[21] ^ d[22] ^ d[31];
  
  assign co[22] =
      c[1] ^ c[10] ^ c[11] ^ c[12] ^ c[19] ^ c[22] ^ 
      c[23] ^ c[28] ^ c[30] ^ c[31] ^ d[0] ^ d[1] ^ d[3] ^ 
      d[8] ^ d[9] ^ d[12] ^ d[19] ^ d[20] ^ d[21] ^ d[30];
  
  assign co[23] =
      c[0] ^ c[2] ^ c[9] ^ c[12] ^ c[13] ^ c[18] ^ 
      c[20] ^ c[21] ^ c[22] ^ c[23] ^ c[24] ^ c[27] ^ c[30] ^ 
      d[1] ^ d[4] ^ d[7] ^ d[8] ^ d[9] ^ d[10] ^ d[11] ^ 
      d[13] ^ d[18] ^ d[19] ^ d[22] ^ d[29] ^ d[31];
  
  assign co[24] =
      c[1] ^ c[3] ^ c[10] ^ c[13] ^ c[14] ^ c[19] ^ 
      c[21] ^ c[22] ^ c[23] ^ c[24] ^ c[25] ^ c[28] ^ c[31] ^ 
      d[0] ^ d[3] ^ d[6] ^ d[7] ^ d[8] ^ d[9] ^ d[10] ^ 
      d[12] ^ d[17] ^ d[18] ^ d[21] ^ d[28] ^ d[30];
  
  assign co[25] =
      c[2] ^ c[4] ^ c[11] ^ c[14] ^ c[15] ^ c[20] ^ 
      c[22] ^ c[23] ^ c[24] ^ c[25] ^ c[26] ^ c[29] ^ d[2] ^ 
      d[5] ^ d[6] ^ d[7] ^ d[8] ^ d[9] ^ d[11] ^ d[16] ^ 
      d[17] ^ d[20] ^ d[27] ^ d[29];
  
  assign co[26] =
      c[3] ^ c[5] ^ c[12] ^ c[15] ^ c[16] ^ c[21] ^ 
      c[23] ^ c[24] ^ c[25] ^ c[26] ^ c[27] ^ c[30] ^ d[1] ^ 
      d[4] ^ d[5] ^ d[6] ^ d[7] ^ d[8] ^ d[10] ^ d[15] ^ 
      d[16] ^ d[19] ^ d[26] ^ d[28];
  
  assign co[27] =
      c[4] ^ c[6] ^ c[13] ^ c[16] ^ c[17] ^ c[22] ^ 
      c[24] ^ c[25] ^ c[26] ^ c[27] ^ c[28] ^ c[31] ^ d[0] ^ 
      d[3] ^ d[4] ^ d[5] ^ d[6] ^ d[7] ^ d[9] ^ d[14] ^ 
      d[15] ^ d[18] ^ d[25] ^ d[27];
  
  assign co[28] =
      c[5] ^ c[7] ^ c[14] ^ c[17] ^ c[18] ^ c[23] ^ 
      c[25] ^ c[26] ^ c[27] ^ c[28] ^ c[29] ^ d[2] ^ d[3] ^ 
      d[4] ^ d[5] ^ d[6] ^ d[8] ^ d[13] ^ d[14] ^ d[17] ^ 
      d[24] ^ d[26];
  
  assign co[29] =
      c[6] ^ c[8] ^ c[15] ^ c[18] ^ c[19] ^ c[24] ^ 
      c[26] ^ c[27] ^ c[28] ^ c[29] ^ c[30] ^ d[1] ^ d[2] ^ 
      d[3] ^ d[4] ^ d[5] ^ d[7] ^ d[12] ^ d[13] ^ d[16] ^ 
      d[23] ^ d[25];
  
  assign co[30] =
      c[7] ^ c[9] ^ c[16] ^ c[19] ^ c[20] ^ c[25] ^ 
      c[27] ^ c[28] ^ c[29] ^ c[30] ^ c[31] ^ d[0] ^ d[1] ^ 
      d[2] ^ d[3] ^ d[4] ^ d[6] ^ d[11] ^ d[12] ^ d[15] ^ 
      d[22] ^ d[24];
  
  assign co[31] =
      c[8] ^ c[10] ^ c[17] ^ c[20] ^ c[21] ^ c[26] ^ 
      c[28] ^ c[29] ^ c[30] ^ c[31] ^ d[0] ^ d[1] ^ d[2] ^ 
      d[3] ^ d[5] ^ d[10] ^ d[11] ^ d[14] ^ d[21] ^ d[23];
  
  endmodule
  
  
  