Subversion Repositories mips_fault_tolerant

library IEEE;

use IEEE.std_logic_1164.all;

entity lfsr is

port (

  clock    : in std_logic;

  reset    : in std_logic;

  sel_top   : in std_logic;

  --                               input

  data_out : out std_logic_vector(63 downto 0)

);

end lfsr;

architecture modular of lfsr is

begin

  process (clock,sel_top)

    variable lfsr_tap : std_logic;

         variable seed : std_logic_vector(63 downto 0);

         variable lfsr_reg : std_logic_vector(63 downto 0);

  begin

    if sel_top = '1' then seed := x"0F0F0F0F0F0F0F0F"; else seed := x"0000000000000000"; end if;

    if clock'EVENT and clock='0' then  --1

      if reset = '1' then  --1

        lfsr_reg := seed;

      else

        lfsr_tap := lfsr_reg(0) xor lfsr_reg(1) xor lfsr_reg(3) xor lfsr_reg(4);

        lfsr_reg := lfsr_reg(62 downto 0) & lfsr_tap;

      end if;

    end if;

         data_out <= lfsr_reg;

  end process;

  --data_out <= lfsr_reg;

end modular;