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--                                                                            --
--                          V H D L    F I L E                                --
--                          COPYRIGHT (C) 2009                                --
--                                                                            --
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--
-- Title       : ROMR
-- Design      : EV_JPEG_ENC
-- Author      : Michal Krepa
--
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--
-- File        : ROMR.VHD
-- Created     : Wed Mar 19 21:09 2009
--
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--
--  Description : Reciprocal of 1/X where X is 1..255
--
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library IEEE; 
  use IEEE.STD_LOGIC_1164.all; 
  use ieee.numeric_std.all; 
 
entity ROMR is 
  generic 
    ( 
      ROMADDR_W     : INTEGER := 8;
      ROMDATA_W     : INTEGER := 16
    );
  port( 
       addr         : in  STD_LOGIC_VECTOR(ROMADDR_W-1 downto 0);
       clk          : in  STD_LOGIC;  
 
       datao        : out STD_LOGIC_VECTOR(ROMDATA_W-1 downto 0) 
  );          
 
end ROMR; 
 
architecture RTL of ROMR is  
 
  constant CK : integer := 256*256;
  type ROMQ_TYPE is array (0 to 2**ROMADDR_W-1) 
            of INTEGER range 0 to 2**ROMDATA_W-1;
 
  constant rom : ROMQ_TYPE := 
  (
           0,
       65535,
       32768,
       21845,
       16384,
       13107,
       10923,
        9362,
        8192,
        7282,
        6554,
        5958,
        5461,
        5041,
        4681,
        4369,
        4096,
        3855,
        3641,
        3449,
        3277,
        3121,
        2979,
        2849,
        2731,
        2621,
        2521,
        2427,
        2341,
        2260,
        2185,
        2114,
        2048,
        1986,
        1928,
        1872,
        1820,
        1771,
        1725,
        1680,
        1638,
        1598,
        1560,
        1524,
        1489,
        1456,
        1425,
        1394,
        1365,
        1337,
        1311,
        1285,
        1260,
        1237,
        1214,
        1192,
        1170,
        1150,
        1130,
        1111,
        1092,
        1074,
        1057,
        1040,
        1024,
        1008,
         993,
         978,
         964,
         950,
         936,
         923,
         910,
         898,
         886,
         874,
         862,
         851,
         840,
         830,
         819,
         809,
         799,
         790,
         780,
         771,
         762,
         753,
         745,
         736,
         728,
         720,
         712,
         705,
         697,
         690,
         683,
         676,
         669,
         662,
         655,
         649,
         643,
         636,
         630,
         624,
         618,
         612,
         607,
         601,
         596,
         590,
         585,
         580,
         575,
         570,
         565,
         560,
         555,
         551,
         546,
         542,
         537,
         533,
         529,
         524,
         520,
         516,
         512,
         508,
         504,
         500,
         496,
         493,
         489,
         485,
         482,
         478,
         475,
         471,
         468,
         465,
         462,
         458,
         455,
         452,
         449,
         446,
         443,
         440,
         437,
         434,
         431,
         428,
         426,
         423,
         420,
         417,
         415,
         412,
         410,
         407,
         405,
         402,
         400,
         397,
         395,
         392,
         390,
         388,
         386,
         383,
         381,
         379,
         377,
         374,
         372,
         370,
         368,
         366,
         364,
         362,
         360,
         358,
         356,
         354,
         352,
         350,
         349,
         347,
         345,
         343,
         341,
         340,
         338,
         336,
         334,
         333,
         331,
         329,
         328,
         326,
         324,
         323,
         321,
         320,
         318,
         317,
         315,
         314,
         312,
         311,
         309,
         308,
         306,
         305,
         303,
         302,
         301,
         299,
         298,
         297,
         295,
         294,
         293,
         291,
         290,
         289,
         287,
         286,
         285,
         284,
         282,
         281,
         280,
         279,
         278,
         277,
         275,
         274,
         273,
         272,
         271,
         270,
         269,
         267,
         266,
         265,
         264,
         263,
         262,
         261,
         260,
         259,
         258,
         257
  );
 
 
 
  signal addr_reg : STD_LOGIC_VECTOR(ROMADDR_W-1 downto 0);
begin   
 
  datao <= STD_LOGIC_VECTOR(TO_UNSIGNED( rom( TO_INTEGER(UNSIGNED(addr_reg)) ), ROMDATA_W)); 
 
  process(clk)
  begin
   if clk = '1' and clk'event then
     addr_reg <= addr;
   end if;
  end process;
 
end RTL;