hamcorr.vhd

   1 library ieee;
   2     use ieee.std_logic_1164.all;
   3     use ieee.std_logic_unsigned.all;
   4
   5 entity hamcorr is
   6     port (
   7         -- TO DO: Make synchronous
   8         du      : in  std_logic_vector(1 to 7);
   9         dc      : out std_logic_vector(1 to 7);
  10         noerror : out std_logic
  11     );
  12 end hamcorr;
  13
  14 architecture hamcorr of hamcorr is
  15
  16 function syndrome (d:std_logic_vector)
  17         return std_logic_vector is
  18     variable syn: std_logic_vector (2 downto 0);
  19     begin
  20     syn(0):= d(1) xor d(3) xor d(5) xor d(7);
  21     syn(1):= d(2) xor d(3) xor d(6) xor d(7);
  22     syn(2):= d(4) xor d(5) xor d(6) xor d(7);
  23     return(syn);
  24 end syndrome;
  25
  26 begin
  27     process(du)
  28     variable i : integer;
  29     begin
  30         dc<=du;
  31         i:=conv_integer(syndrome(du));
  32         if i=0 then noerror <='1';
  33         else noerror <='0'; dc(i) <=not du(i); end if;
  34     end process;
  35 end hamcorr;