Subversion Repositories mips_fault_tolerant

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-- Company: 

-- Engineer:       Lazaridis Dimitris

-- 

-- Create Date:    00:18:51 04/23/2012 

-- Design Name: 

-- Module Name:    Shift - Behavioral 

-- Project Name: 

-- Target Devices: 

-- Tool versions: 

-- Description: 

--

-- Dependencies: 

--

-- Revision: 

-- Revision 0.01 - File Created

-- Additional Comments: 

--

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library IEEE;

use IEEE.STD_LOGIC_1164.ALL;

use IEEE.numeric_std.all;

use IEEE.STD_LOGIC_UNSIGNED.ALL;

--use IEEE.Std_logic_arith.all;

-- Uncomment the following library declaration if using

-- arithmetic functions with Signed or Unsigned values

--use IEEE.NUMERIC_STD.ALL;

-- Uncomment the following library declaration if instantiating

-- any Xilinx primitives in this code.

--library UNISIM;

--use UNISIM.VComponents.all;

entity Shift is

Port

(

           rst : in  STD_LOGIC;

                          B : in  STD_LOGIC_VECTOR (31 downto 0);

           ALUop : in  STD_LOGIC_VECTOR (1 downto 0);

           Shamt_in : in  STD_LOGIC_VECTOR (4 downto 0);

           S : out  STD_LOGIC_VECTOR (31 downto 0)

);

end Shift;

architecture Behavioral of Shift is

begin

sht:process(rst,ALUop,B,Shamt_in)

variable to_int: integer;

variable shift_temp : STD_LOGIC_VECTOR (31 downto 0);

begin

          if rst = '0' then

             S <= x"00000000";

          else

     to_int := CONV_INTEGER(Shamt_in);

          case ALUop is

                                    when "00" => shift_temp := std_logic_vector(unsigned(B) sll to_int); --shift_B sll 

                                         when "01" => shift_temp := B;

                                         when "10" => shift_temp := std_logic_vector(unsigned(B) srl to_int); --srl to_int; 

                                         when "11" => shift_temp := to_stdlogicvector(to_bitvector(B) sra to_int);--sra to_int;  

                                         when others => S <=(others=>'0');

          end case;

          end if;

 S <= shift_temp;

end process sht;

end Behavioral;