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//*****************************************************************************
//   ____  ____
//  /   /\/   /
// /___/  \  /    Vendor: Xilinx
// \   \   \/     Version: %version
//  \   \         Application: MIG
//  /   /         Filename: data_prbs_gen.v
// /___/   /\     Date Last Modified: $Date: 2009/11/03 04:41:58 $
// \   \  /  \    Date Created: Fri Sep 01 2006
//  \___\/\___\
//
//Device: Spartan6
//Design Name: DDR/DDR2/DDR3/LPDDR 
//Purpose:  This module is used LFSR to generate random data for memory 
//          data write or memory data read comparison.The first data is 
//          seeded by the input prbs_seed_i which is connected to memory address.
//Reference:
//Revision History:
//*****************************************************************************

`timescale 1ps/1ps

module data_prbs_gen #
  (
    parameter TCQ           = 100,

    parameter EYE_TEST   = "FALSE",
    parameter PRBS_WIDTH = 32,                                                                       // "SEQUENTIAL_BUrst_i"
    parameter SEED_WIDTH = 32    
   )
  (
   input           clk_i,
   input           clk_en,
   input           rst_i,
   input [31:0] prbs_fseed_i,
   input           prbs_seed_init,  // when high the prbs_x_seed will be loaded
   input [PRBS_WIDTH - 1:0]  prbs_seed_i,
   
   output  [PRBS_WIDTH - 1:0]  prbs_o     // generated address
  );
  
reg [PRBS_WIDTH - 1 :0] prbs;  
reg [PRBS_WIDTH :1] lfsr_q;
integer i;



always @ (posedge clk_i)
begin
   if (prbs_seed_init && EYE_TEST == "FALSE"  || rst_i )  //reset it to a known good state to prevent it locks up
//   if (rst_i )  //reset it to a known good state to prevent it locks up

      begin
        lfsr_q <= #TCQ  {prbs_seed_i + prbs_fseed_i[31:0] + 32'h55555555};

      end
   else   if (clk_en) begin
     
        lfsr_q[32:9] <= #TCQ  lfsr_q[31:8];
        lfsr_q[8]    <= #TCQ  lfsr_q[32] ^ lfsr_q[7];
        lfsr_q[7]    <= #TCQ  lfsr_q[32] ^ lfsr_q[6];
        lfsr_q[6:4]  <= #TCQ  lfsr_q[5:3];
        
        lfsr_q[3]    <= #TCQ  lfsr_q[32] ^ lfsr_q[2];
        lfsr_q[2]    <= #TCQ  lfsr_q[1] ;
        lfsr_q[1]    <= #TCQ  lfsr_q[32];
       
        
         end
end
 
always @ (lfsr_q[PRBS_WIDTH:1]) begin
       prbs = lfsr_q[PRBS_WIDTH:1];
end

assign prbs_o = prbs;

endmodule
   
         
