`timescale 1ns / 1ps

//////////////////////////////////////////////////////////////////////////////////
// Company: BITSILICA PRIVATE LIMITED
// Design Name: ENCODER BIT SELECTION
// Module Name: encoder_bit_selection_rtl
// Project Name: POLAR ENCODER-DECODER
// Target Devices: Zynq UltraScale+ ZCU111 Evaluation Platform (xczu28dr-ffvg1517-2-e)
// Tool Versions: VIVADO 2020.1
// Description: RTL code for bit selection, in order to change the length of a sequence from N to E,
// also known as rate matching.
//
// 
//////////////////////////////////////////////////////////////////////////////////
module encoder_bit_selection_rtl
#(
  parameter K = 164,                                  
  parameter G = 1728,
  parameter C = 1,
  parameter E = G/C,
  parameter N=512                                        
  )
 (
  input wire          clock_i,                               // system clock
  input wire          reset_ni,                              // active low synchronous reset
  input  wire [N-1:0] msg_i,                                 // input message for bit selection
  output  reg [E-1:0] msg_o                                  // output message bit selection
 );

  localparam Y = E/N;
  localparam Z = E%N;	
							
  integer i;

  generate 
    always@(posedge clock_i) begin
      if(!reset_ni )begin
          msg_o <= 0;
        end    
      else begin
       if(E>=N) 
          begin
              for(i = 1;i <= Y;i = i+1)                    // Repitition //
                msg_o[((i*N)-1) -: N]<=msg_i[N-1:0];	   // Assigning same N bits to output reg for E/N times
                if(Z != 0)begin
                  msg_o[E-1:N*(Y)] <= msg_i[Z-1:0];        // Assingning remaining E%N bits
              end
          end   
         else 
          begin				
           if((10000*(K/E)) <= (70000/16))                 // Puncturing //
             msg_o[E-1:0] <= msg_i[N-1:N-E]; 			   // Assigning last E bits to output register
           else 								           // Shortening //
             msg_o[E-1:0] <= msg_i[E-1:0];                 // Assigning first E bits to output register
       end  
      end
    end
  endgenerate

endmodule