Subversion Repositories System09

----------------------------------------------------------------------------
--	btn_debounce.vhd -- Button Debouncer
----------------------------------------------------------------------------
-- Author:  Sam Bobrowicz
--          Copyright 2011 Digilent, Inc.
----------------------------------------------------------------------------
--
----------------------------------------------------------------------------
--	This component is used to debounce signals generated by external push
-- buttons. It is designed to independently debounce 5 Push button signals.
-- Debouncing is done by only registering a change in a button state if 
-- it remains constant for 2^16 clock cycles. 
--         				
-- Port Descriptions:
--
--   BTN_I - The input button signals
--    CLK  - Behavior is optimized for a 100 MHz clock
--   BTN_O - The debounced button signals
--   											
----------------------------------------------------------------------------
--
----------------------------------------------------------------------------
-- Revision History:
--  08/08/2011(SamB): Created using Xilinx Tools 13.2
----------------------------------------------------------------------------
 
library IEEE;
use IEEE.STD_LOGIC_1164.ALL;
use IEEE.std_logic_unsigned.all;
 
entity btn_debounce is
    Port ( BTN_I : in  STD_LOGIC_VECTOR (3 downto 0);
           CLK : in  STD_LOGIC;
           BTN_O : out  STD_LOGIC_VECTOR (3 downto 0));
end btn_debounce;
 
architecture Behavioral of btn_debounce is
 
constant CNTR_MAX : std_logic_vector(15 downto 0) := (others => '1');
 
signal btn0_cntr : std_logic_vector(15 downto 0) := (others => '0');
signal btn1_cntr : std_logic_vector(15 downto 0) := (others => '0');
signal btn2_cntr : std_logic_vector(15 downto 0) := (others => '0');
signal btn3_cntr : std_logic_vector(15 downto 0) := (others => '0');
 
 
signal btn0_reg : std_logic := '0';
signal btn1_reg : std_logic := '0';
signal btn2_reg : std_logic := '0';
signal btn3_reg : std_logic := '0';
 
begin
 
btn0_debounce_process : process (CLK)
begin
	if (rising_edge(CLK)) then
		if (btn0_cntr = CNTR_MAX) then
			btn0_reg <= not(btn0_reg);
		end if;
	end if;
end process;
 
btn0_counter_process : process (CLK)
begin
	if (rising_edge(CLK)) then
		if ((btn0_reg = '1') xor (BTN_I(0) = '1')) then
			if (btn0_cntr = CNTR_MAX) then
				btn0_cntr <= (others => '0');
			else
				btn0_cntr <= btn0_cntr + 1;
			end if;
		else
			btn0_cntr <= (others => '0');
		end if;
	end if;
end process;
 
btn1_debounce_process : process (CLK)
begin
	if (rising_edge(CLK)) then
		if (btn1_cntr = CNTR_MAX) then
			btn1_reg <= not(btn1_reg);
		end if;
	end if;
end process;
 
btn1_counter_process : process (CLK)
begin
	if (rising_edge(CLK)) then
		if ((btn1_reg = '1') xor (BTN_I(1) = '1')) then
			if (btn1_cntr = CNTR_MAX) then
				btn1_cntr <= (others => '0');
			else
				btn1_cntr <= btn1_cntr + 1;
			end if;
		else
			btn1_cntr <= (others => '0');
		end if;
	end if;
end process;
 
btn2_debounce_process : process (CLK)
begin
	if (rising_edge(CLK)) then
		if (btn2_cntr = CNTR_MAX) then
			btn2_reg <= not(btn2_reg);
		end if;
	end if;
end process;
 
btn2_counter_process : process (CLK)
begin
	if (rising_edge(CLK)) then
		if ((btn2_reg = '1') xor (BTN_I(2) = '1')) then
			if (btn2_cntr = CNTR_MAX) then
				btn2_cntr <= (others => '0');
			else
				btn2_cntr <= btn2_cntr + 1;
			end if;
		else
			btn2_cntr <= (others => '0');
		end if;
	end if;
end process;
 
btn3_debounce_process : process (CLK)
begin
	if (rising_edge(CLK)) then
		if (btn3_cntr = CNTR_MAX) then
			btn3_reg <= not(btn3_reg);
		end if;
	end if;
end process;
 
btn3_counter_process : process (CLK)
begin
	if (rising_edge(CLK)) then
		if ((btn3_reg = '1') xor (BTN_I(3) = '1')) then
			if (btn3_cntr = CNTR_MAX) then
				btn3_cntr <= (others => '0');
			else
				btn3_cntr <= btn3_cntr + 1;
			end if;
		else
			btn3_cntr <= (others => '0');
		end if;
	end if;
end process;
 
 
 
BTN_O <= btn3_reg & btn2_reg & btn1_reg & btn0_reg;
 
end Behavioral;