debouncer.vhd

This is a project about PWM. Application in motor speed control

----------------------------------------------------------------------------
-- debouncer for buttons 
-- variable bounce window ("period")
----------------------------------------------------------------------------

library IEEE;
use IEEE.STD_LOGIC_1164.ALL;
use IEEE.STD_LOGIC_ARITH.ALL;
use IEEE.STD_LOGIC_UNSIGNED.ALL;

entity debouncer is
  port(
    clk: in std_logic;
    raw: in std_logic;
    period: in std_logic_vector(31 downto 0);
    debounced: out std_logic
  );
end debouncer;

architecture behavior of debouncer is
type statetype is (standby, pressed, released);
signal state: statetype := standby;
signal count: std_logic_vector(31 downto 0);

begin
  process
    begin
      wait until rising_edge(clk);
      case state is

        when standby =>
          if (raw = '1') then
            state <= pressed;
            debounced <= '1';
            count <= (others => '0');
          end if;                           

        when pressed =>
          if (count < period) then
            count <= count + 1;
          elsif (raw = '0') then
            count <= (others => '0');
            state <= released;
          end if;

        when released =>
          debounced <= '0';
          if (count < period) then
            count <= count + 1;
          else
	    state <= standby;
          end if; 
      end case;
    end process;
end behavior;