www.pudn.com > jaguar2s.zip > LSHIFTER.VHD

--************************************************************ 
--************************************************************ 
--*----------------------------------------------------------* 
--*|Version                           :1.0                   | 
--*|Date of Last Revision             :12/23/1998            | 
--*----------------------------------------------------------* 
--************************************************************ 
-- Copyright (C) 1999 Drey Enterprises Inc.   All Rights Reserved. 
--************************************************************ 
-- Warning: This file is protected by Federal Copyright Law, 
-- with all rights reserved. It is unlawful to reproduce 
-- any parts of this file, in any form, without expressed 
-- written permission from Drey Enterprises Inc. This Copyright 
-- is actively enforced. 
--************************************************************ 
--************************************************************ 
 
library ieee;  
use ieee.std_logic_1164.all;  
 
entity Lshifter is  
     generic( 
         EXP_WIDTH      :integer := 5; 
         WORD_WIDTH     :integer := 32 
     ); 
     port(  
          shftval       :in std_logic_vector(EXP_WIDTH-1 downto 0); 
          a             :in std_logic_vector(WORD_WIDTH/2-1 downto 0);  
          b             :out std_logic_vector(WORD_WIDTH/2-1 downto 0) 
     );  
end Lshifter;  
 
architecture behavior of Lshifter is  
  
begin  
 
    process(shftval,a) 
         variable i,j    :integer; 
         variable a_prev :std_logic_vector(WORD_WIDTH/2-1 downto 0); 
         variable a_next :std_logic_vector(WORD_WIDTH/2-1 downto 0); 
         variable pow2   :integer; 
    begin 
         a_prev := a; 
         pow2:=1; 
         for i in 0 to EXP_WIDTH-1 loop 
             for j in 0 to WORD_WIDTH/2-1 loop 
                  if (shftval(i) = '1') then 
                      if (j-pow2 < 0) then 
                          a_next(j) := '0'; 
                      else 
                          a_next(j) := a_prev(j-pow2); 
                      end if; 
                  else 
                      a_next(j) := a_prev(j); 
                  end if; 
             end loop; 
             a_prev := a_next; 
             pow2:= pow2*2; 
         end loop; 
         b <= a_next; 
    end process; 
 
end behavior;