/* -----------------------------------------------------------------------------------
 * Module Name  : crc16_ccitt
 * Generated by : https://github.com/PXVI/ip_parallel_custom_crc_gerator_verilog
 * Author       : pxvi
 * Description  : Parallel CRC( 16-bit ) module with 16-bit data input. 
 *                Polynomial Degrees [ 16 12 5 0 ]
 * -----------------------------------------------------------------------------------
 * 
 * MIT License
 * 
 * Copyright (c) 2024 k-sva
 * 
 * Permission is hereby granted, free of charge, to any person obtaining a copy
 * of this software and associated documentation files (the Software), to deal
 * in the Software without restriction, including without limitation the rights
 * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
 * copies of the Software, and to permit persons to whom the Software is
 * furnished to do so, subject to the following conditions:
 * 
 * The above copyright notice and this permission notice shall be included in all
 * copies or substantial portions of the Software.
 * 
 * THE SOFTWARE IS PROVIDED AS IS, WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
 * SOFTWARE.
 * 
 * ----------------------------------------------------------------------------------- */
module crc16_ccitt  #(  parameter   RESET_SEED = 'hffff )(
                                                                            input wire CLK,
                                                                            input wire RSTn,

                                                                            input wire [15:0] data_in,
                                                                            input wire enable,
                                                                            input wire clear,

                                                                            output [15:0] CRC
                                                                        );


     reg [16-1:0] Mout_p, Mout_n;

    always@( posedge CLK )
    begin
        Mout_p <= Mout_n;

        if( !RSTn )
        begin
            Mout_p <= RESET_SEED;
        end
    end

    always@( * )
    begin
        Mout_n = Mout_p;

        if( clear )
        begin
            Mout_n = RESET_SEED;
        end
        else if( enable )
        begin
            Mout_n[0] = data_in[0] ^ data_in[4] ^ data_in[8] ^ data_in[11] ^ data_in[12] ^ Mout_p[0] ^ Mout_p[4] ^ Mout_p[8] ^ Mout_p[11] ^ Mout_p[12] ;
            Mout_n[1] = data_in[1] ^ data_in[5] ^ data_in[9] ^ data_in[12] ^ data_in[13] ^ Mout_p[1] ^ Mout_p[5] ^ Mout_p[9] ^ Mout_p[12] ^ Mout_p[13] ;
            Mout_n[2] = data_in[2] ^ data_in[6] ^ data_in[10] ^ data_in[13] ^ data_in[14] ^ Mout_p[2] ^ Mout_p[6] ^ Mout_p[10] ^ Mout_p[13] ^ Mout_p[14] ;
            Mout_n[3] = data_in[3] ^ data_in[7] ^ data_in[11] ^ data_in[14] ^ data_in[15] ^ Mout_p[3] ^ Mout_p[7] ^ Mout_p[11] ^ Mout_p[14] ^ Mout_p[15] ;
            Mout_n[4] = data_in[4] ^ data_in[8] ^ data_in[12] ^ data_in[15] ^ Mout_p[4] ^ Mout_p[8] ^ Mout_p[12] ^ Mout_p[15] ;
            Mout_n[5] = data_in[0] ^ data_in[4] ^ data_in[5] ^ data_in[8] ^ data_in[9] ^ data_in[11] ^ data_in[12] ^ data_in[13] ^ Mout_p[0] ^ Mout_p[4] ^ Mout_p[5] ^ Mout_p[8] ^ Mout_p[9] ^ Mout_p[11] ^ Mout_p[12] ^ Mout_p[13] ;
            Mout_n[6] = data_in[1] ^ data_in[5] ^ data_in[6] ^ data_in[9] ^ data_in[10] ^ data_in[12] ^ data_in[13] ^ data_in[14] ^ Mout_p[1] ^ Mout_p[5] ^ Mout_p[6] ^ Mout_p[9] ^ Mout_p[10] ^ Mout_p[12] ^ Mout_p[13] ^ Mout_p[14] ;
            Mout_n[7] = data_in[2] ^ data_in[6] ^ data_in[7] ^ data_in[10] ^ data_in[11] ^ data_in[13] ^ data_in[14] ^ data_in[15] ^ Mout_p[2] ^ Mout_p[6] ^ Mout_p[7] ^ Mout_p[10] ^ Mout_p[11] ^ Mout_p[13] ^ Mout_p[14] ^ Mout_p[15] ;
            Mout_n[8] = data_in[3] ^ data_in[7] ^ data_in[8] ^ data_in[11] ^ data_in[12] ^ data_in[14] ^ data_in[15] ^ Mout_p[3] ^ Mout_p[7] ^ Mout_p[8] ^ Mout_p[11] ^ Mout_p[12] ^ Mout_p[14] ^ Mout_p[15] ;
            Mout_n[9] = data_in[4] ^ data_in[8] ^ data_in[9] ^ data_in[12] ^ data_in[13] ^ data_in[15] ^ Mout_p[4] ^ Mout_p[8] ^ Mout_p[9] ^ Mout_p[12] ^ Mout_p[13] ^ Mout_p[15] ;
            Mout_n[10] = data_in[5] ^ data_in[9] ^ data_in[10] ^ data_in[13] ^ data_in[14] ^ Mout_p[5] ^ Mout_p[9] ^ Mout_p[10] ^ Mout_p[13] ^ Mout_p[14] ;
            Mout_n[11] = data_in[6] ^ data_in[10] ^ data_in[11] ^ data_in[14] ^ data_in[15] ^ Mout_p[6] ^ Mout_p[10] ^ Mout_p[11] ^ Mout_p[14] ^ Mout_p[15] ;
            Mout_n[12] = data_in[0] ^ data_in[4] ^ data_in[7] ^ data_in[8] ^ data_in[15] ^ Mout_p[0] ^ Mout_p[4] ^ Mout_p[7] ^ Mout_p[8] ^ Mout_p[15] ;
            Mout_n[13] = data_in[1] ^ data_in[5] ^ data_in[8] ^ data_in[9] ^ Mout_p[1] ^ Mout_p[5] ^ Mout_p[8] ^ Mout_p[9] ;
            Mout_n[14] = data_in[2] ^ data_in[6] ^ data_in[9] ^ data_in[10] ^ Mout_p[2] ^ Mout_p[6] ^ Mout_p[9] ^ Mout_p[10] ;
            Mout_n[15] = data_in[3] ^ data_in[7] ^ data_in[10] ^ data_in[11] ^ Mout_p[3] ^ Mout_p[7] ^ Mout_p[10] ^ Mout_p[11] ;
        end
    end

    assign CRC = Mout_p;
endmodule