Below code is 16-bit CRC-CCITT implementation, with following features

• Width = 16 bits
• Truncated polynomial = 0x1021
• Initial value = 0xFFFF
• Input data is NOT reflected
• Output CRC is NOT reflected
• No XOR is performed on the output CRC

  1 //-----------------------------------------------------
  2 // Design Name : serial_crc_ccitt
  3 // File Name   : serial_crc.v
  4 // Function    : CCITT Serial CRC
  5 // Coder       : Deepak Kumar Tala
  6 //-----------------------------------------------------
  7 module serial_crc_ccitt (
  8 clk     ,
  9 reset   ,
 10 enable  ,
 11 init    , 
 12 data_in , 
 13 crc_out
 14 );
 15 //-----------Input Ports---------------
 16 input clk     ;
 17 input reset   ;
 18 input enable  ;
 19 input init    ;
 20 input data_in ;
 21 //-----------Output Ports---------------
 22 output [15:0] crc_out;
 23 //------------Internal Variables--------
 24 reg   [15:0] lfsr;
 25 //-------------Code Start-----------------
 26 assign crc_out = lfsr;
 27 // Logic to CRC Calculation
 28 always @ (posedge clk)
 29 if (reset) begin
 30   lfsr <= 16'hFFFF;
 31 end else if (enable) begin
 32   if (init) begin
 33     lfsr <=  16'hFFFF;
 34   end else begin
 35     lfsr[0]  <= data_in ^ lfsr[15];
 36     lfsr[1]  <= lfsr[0];
 37     lfsr[2]  <= lfsr[1];
 38     lfsr[3]  <= lfsr[2];
 39     lfsr[4]  <= lfsr[3];
 40     lfsr[5]  <= lfsr[4] ^ data_in ^ lfsr[15];
 41     lfsr[6]  <= lfsr[5];
 42     lfsr[7]  <= lfsr[6];
 43     lfsr[8]  <= lfsr[7];
 44     lfsr[9]  <= lfsr[8];
 45     lfsr[10] <= lfsr[9];
 46     lfsr[11] <= lfsr[10];
 47     lfsr[12] <= lfsr[11] ^ data_in ^ lfsr[15];
 48     lfsr[13] <= lfsr[12];
 49     lfsr[14] <= lfsr[13];
 50     lfsr[15] <= lfsr[14];
 51   end
 52 end 
 53 
 54 endmodule

Copyright © 1998-2014

Deepak Kumar Tala - All rights reserved

Do you have any Comment? mail me at:deepak@asic-world.com