----------------------------------------------------------
-- keyDebounce
-- Author   : Gautam Karnik
-- Date     : March 30, 2001
-- Filename : keyDebounce.vhd
-- Architecture : Behavioral
-- Description  : This entity is the key debounce 
--                control unit for the keypad. 
--                It simply counts to "3FFFFF", when the
--                sense line is 0.  When we hit the 
--                threshold value we know a key has been
--                pressed and we signal the rest of the
--                system.
----------------------------------------------------------

library ieee;
use ieee.std_logic_1164.all;
use ieee.std_logic_arith.all; 
use ieee.std_logic_unsigned.all; 
library work;
use work.CDMA_pkg.all;

entity keyDebounce is
      	port ( resetn  : in std_logic;
			   clock  : in std_logic;
			   sense  : in std_logic;
			   keyPressed : out std_logic
      	     );
end entity keyDebounce;

architecture behavioral of keyDebounce is 

signal count : std_logic_vector ( 23 downto 0);
begin

debounce_test : process (clock, resetn ) is
  -- user 16 bit counter to approximate 5 ms
begin
   wait until rising_edge ( clock );
   if ( resetn = '0' ) then
	  count    <= (others => '0');
   else
	  -- if we something has been pressed on the keypad begin the counter	
	  if ( sense = '0' ) then
 	    count <= count + '1';    
		if count = x"3FFFFF" then
			KeyPressed <= '1';
		else
			KeyPressed <= '0';
		end if;
	  elsif ( sense = '1' ) then
	    count <= ( others => '0' );
	  end if;
   end if;
end process debounce_test;

-- with count select
--	keyPressed <= '1' when X"3FFFFF", -- time constant, changed for testing
--				  '0' when others;

end behavioral;