lcd display

hi i'm beginner to vhdl. i'm write a vhdl code to display characters on lcd using de2 board. it display different characters for different input from 000 to 111.

i'm already compile the code in quartus and there are no error. however when i download the program on de2 board the lcd was not display anything.

where am i done wrong....please help me...tq

library ieee;

use ieee.std_logic_1164.all;

use ieee.std_logic_arith.all;

use ieee.std_logic_unsigned.all;

entity lcd is

port ( w : in std_logic_vector( 2 downto 0);

rs : out bit;

rw : out bit;

db : out bit_vector(7 downto 0);

lcd_on :out bit;

lcd_blon : out bit);

end lcd;

architecture main of lcd is

signal output : std_logic_vector(2 downto 0);

begin

process(output)

begin

lcd_on<='1';

lcd_blon<='1';

output <= w;

case output is

when "000"=>

rs<='1';

rw<='0';

db<=x"4E",x"4F",x"52",x"4D",x"41",x"4C";

when "001"=>

rs<='1';

rw<='0';

db<=x"4C",x"45",x"56",x"45",x"4C",x"20",x"31";

when "010"=>

rs<='1';

rw<='0';

db<=x"4C",x"45",x"56",x"45",x"4C",x"20",x"32";

when "011"=>

rs<='1';

rw<='0';

db<=x"4D",x"4F",x"44",x"45",x"52",x"41",x"54",x"45";

when "100"=>

rs<='1';

rw<='0';

db<=x"46",x"4C",x"4F",x"4F",x"44",x"20",x"5A",x"4F",x"4E",x"45";

when "101"=>

rs<='1';

rw<='0';

db<=x"44",x"41",x"4E",x"47",x"45",x"52",x"20",x"5A",x"4F",x"4E",x"45";

when "110"=>

rs<='1';

rw<='0';

db<=x"45",x"58",x"54",x"52",x"45",x"4D",x"45",x"4C",x"59",x"20",x"44",x"41",x"4E",x"47",x"45",x"52";

when "111"=>

rs<='1';

rw<='0';

db<=x"4D",x"41",x"58",x"49",x"4D",x"55",x"4D",x"20",x"5A",x"4F",x"4E",x"45";

end case;

end process;

end main;