----------------------------------------------------------------------------------
-- Massimiliano De Gaspari
-- 10 August 2006
-- sends a Reset signal when a block is in "busy" state for more than Timeout milliseconds
----------------------------------------------------------------------------------
library IEEE;
use IEEE.STD_LOGIC_1164.ALL;
use IEEE.STD_LOGIC_ARITH.ALL;
use IEEE.STD_LOGIC_UNSIGNED.ALL;

entity AutoReset is
    Port ( BusyIn    : in  STD_LOGIC;
           AutoReset : out  STD_LOGIC;
           Clk       : in  STD_LOGIC);
end AutoReset;

architecture Behavioral of AutoReset is

type States is (Idle, bs, en1, en2);
signal RState : States;

constant Timeout : integer:=500;         -- in milliseconds
constant Max : integer:=Timeout*40000;   -- for Clk frequency 40MHz
signal Counter: integer range 0 to Max;

begin
process (Clk)
begin
	if rising_edge(Clk) then
		case RState is
		when Idle =>
			AutoReset <= '0';
			if BusyIn = '1' then 
				RState <= bs;
			else
				RState <= Idle;
			end if;
		when bs =>
			if BusyIn ='0' then
				RState <= Idle;
				Counter <= 0;
			else
				if Counter = Max then
					AutoReset <= '1';
					RState <= en1;
					Counter <= 0;
				else Counter <= Counter +1;
				end if;
			end if;
		when en1 =>
			RState <= en2;
		when en2 =>
			AutoReset <= '0';
			RState <= Idle;
		when others => RState <= Idle;
		end case;
	end if;
end process;
end Behavioral;