CRC/encoder_crc_attachment.srcs/sources_1/new/crc_gen.sv

`timescale 1ns / 1ps

          
module crc_gen #(
            parameter int          CRC_SIZE   = 24,
            parameter int          DATA_WIDTH = 140,
            parameter bit [63 : 0] INIT       = 'h0
          )(
            input                           clk_i,
            input                           rst_n,
//            input  [24:0]                   POLY,
            input  [7:0]                    a_in,               // Number of valid bits on input
            input  [7:0]                    k_in,               // Number of valid bits on output  
            input  [DATA_WIDTH - 1 : 0]     data_i,             // Input Information bit 
            output reg [CRC_SIZE - 1 : 0]   crc_o               // output CRC of information Input
          );
          
          logic [CRC_SIZE - 1 : 0] crc = 0;
          logic [CRC_SIZE - 1 : 0] crc_next;
          logic [CRC_SIZE - 1 : 0] crc_prev;
            
          reg [24:0] POLY = 'h1B2B117;        
          
          reg [DATA_WIDTH-1:0]valid_data;
          
          reg [7:0]valid_count = 0;
          
          always_ff @( posedge clk_i )
            if( !rst_n )begin
              crc_o <= INIT[CRC_SIZE - 1 : 0];
              valid_data <= 'b0;
             end
            else
            begin
 //              crc_o <= crc_prev;
     for(valid_count = 0; valid_count < 140; valid_count = valid_count + 1)
     if(valid_count <= a_in)
        valid_data[valid_count] = data_i[valid_count];//;data_i[1*a_in +: 1];
     else
        valid_data[valid_count] = 1'b0;  
                crc_o <= crc_prev;

            end  
            
            
          generate
           always_comb
             begin
               crc_next = crc;
               crc_prev = crc;
               for( int i = 0; i < DATA_WIDTH; i ++ )
                 begin
                   $display("Inside for Loop");
                   crc_next[0] = crc_prev[CRC_SIZE - 1] ^ valid_data[DATA_WIDTH - 1 - i];
                   $display("crc_next[%d] = %b",i,crc_next[i]); 
                   for( int j = 1; j < CRC_SIZE; j++ )
                     if( POLY[j] )
                       crc_next[j] = crc_prev[j - 1] ^ crc_prev[CRC_SIZE - 1] ^ valid_data[DATA_WIDTH - 1 - i];
                     else
                       crc_next[j] = crc_prev[j - 1];
                   crc_prev = crc_next;
                 end
               end
          
          endgenerate
endmodule