| 1 |
2 |
lal87 |
----------------------------------------------------------------------------
|
| 2 |
|
|
---- Create Date: 13:06:08 07/28/2010 ----
|
| 3 |
|
|
---- Design Name: lfsr ----
|
| 4 |
|
|
---- Project Name: lfsr_randgen ----
|
| 5 |
|
|
---- Description: ----
|
| 6 |
|
|
---- A random number generator based on linear feedback shift ----
|
| 7 |
|
|
---- register(LFSR).A LFSR is a shift register whose input bit is a ----
|
| 8 |
|
|
---- linear function of its previous state.The detailed documentation ----
|
| 9 |
|
|
---- is available in the file named manual.pdf. ----
|
| 10 |
|
|
---- ----
|
| 11 |
|
|
----------------------------------------------------------------------------
|
| 12 |
|
|
---- ----
|
| 13 |
|
|
---- This file is a part of the lfsr_randgen project at ----
|
| 14 |
|
|
---- http://www.opencores.org/ ----
|
| 15 |
|
|
---- ----
|
| 16 |
|
|
---- Author(s): ----
|
| 17 |
|
|
---- Vipin Lal, lalnitt@gmail.com ----
|
| 18 |
|
|
---- ----
|
| 19 |
|
|
----------------------------------------------------------------------------
|
| 20 |
|
|
---- ----
|
| 21 |
|
|
---- Copyright (C) 2010 Authors and OPENCORES.ORG ----
|
| 22 |
|
|
---- ----
|
| 23 |
|
|
---- This source file may be used and distributed without ----
|
| 24 |
|
|
---- restriction provided that this copyright statement is not ----
|
| 25 |
|
|
---- removed from the file and that any derivative work contains ----
|
| 26 |
|
|
---- the original copyright notice and the associated disclaimer. ----
|
| 27 |
|
|
---- ----
|
| 28 |
|
|
---- This source file is free software; you can redistribute it ----
|
| 29 |
|
|
---- and/or modify it under the terms of the GNU Lesser General ----
|
| 30 |
|
|
---- Public License as published by the Free Software Foundation; ----
|
| 31 |
|
|
---- either version 2.1 of the License, or (at your option) any ----
|
| 32 |
|
|
---- later version. ----
|
| 33 |
|
|
---- ----
|
| 34 |
|
|
---- This source is distributed in the hope that it will be ----
|
| 35 |
|
|
---- useful, but WITHOUT ANY WARRANTY; without even the implied ----
|
| 36 |
|
|
---- warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR ----
|
| 37 |
|
|
---- PURPOSE. See the GNU Lesser General Public License for more ----
|
| 38 |
|
|
---- details. ----
|
| 39 |
|
|
---- ----
|
| 40 |
|
|
---- You should have received a copy of the GNU Lesser General ----
|
| 41 |
|
|
---- Public License along with this source; if not, download it ----
|
| 42 |
|
|
---- from http://www.opencores.org/lgpl.shtml ----
|
| 43 |
|
|
---- ----
|
| 44 |
|
|
----------------------------------------------------------------------------
|
| 45 |
|
|
|
| 46 |
|
|
library ieee;
|
| 47 |
|
|
use ieee.std_logic_1164.all;
|
| 48 |
|
|
use ieee.std_logic_arith.all;
|
| 49 |
|
|
use ieee.std_logic_unsigned.all;
|
| 50 |
|
|
library work;
|
| 51 |
|
|
use work.lfsr_pkg.ALL;
|
| 52 |
|
|
|
| 53 |
|
|
entity lfsr is
|
| 54 |
|
|
generic (width : integer := 32);
|
| 55 |
|
|
port (clk : in std_logic;
|
| 56 |
|
|
set_seed : in std_logic;
|
| 57 |
|
|
out_enable : in std_logic;
|
| 58 |
|
|
seed : in std_logic_vector(width-1 downto 0);
|
| 59 |
|
|
rand_out : out std_logic_vector(width-1 downto 0)
|
| 60 |
|
|
);
|
| 61 |
|
|
end lfsr;
|
| 62 |
|
|
|
| 63 |
|
|
architecture Behavioral of lfsr is
|
| 64 |
|
|
|
| 65 |
|
|
begin
|
| 66 |
|
|
|
| 67 |
|
|
process(clk,set_seed,out_enable,seed)
|
| 68 |
|
|
|
| 69 |
|
|
variable rand_temp : std_logic_vector (width-1 downto 0):=(0 => '1',others => '0');
|
| 70 |
|
|
variable temp : std_logic := '0';
|
| 71 |
|
|
|
| 72 |
|
|
begin
|
| 73 |
|
|
if(set_seed = '1') then
|
| 74 |
|
|
rand_temp := seed;
|
| 75 |
|
|
elsif(rising_edge(clk)) then
|
| 76 |
|
|
temp := xor_gates(rand_temp);
|
| 77 |
|
|
rand_temp(width-1 downto 1) := rand_temp(width-2 downto 0);
|
| 78 |
|
|
rand_temp(0) := temp;
|
| 79 |
|
|
end if;
|
| 80 |
|
|
|
| 81 |
|
|
if(out_enable ='1') then
|
| 82 |
|
|
rand_out <= rand_temp;
|
| 83 |
|
|
else
|
| 84 |
|
|
rand_out <= (others => '0');
|
| 85 |
|
|
end if;
|
| 86 |
|
|
|
| 87 |
|
|
end process;
|
| 88 |
|
|
|
| 89 |
|
|
end Behavioral;
|
| 90 |
|
|
|
