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

--this component acts as an external timer for the microblaze processor.
--It will generate a steady pulse train of interrupts at a specified rate.

entity timer is
    Port ( clock_i : in  STD_LOGIC;
           reset_i : in  STD_LOGIC;
           interrupt_o : out  STD_LOGIC);
end timer;

architecture Behavioral of timer is

begin

process(clock_i)
	variable count : integer := 0;
	variable interrupt : std_logic := '0';
	constant LIMIT : integer := 25000; --1 millisecond for a MicroBlaze at 25 MHz
begin
	if (clock_i='1' and clock_i'event) then
		if (reset_i = '1') then
			count := 0;
			interrupt := '0';
		else
			if (count = LIMIT) then
				interrupt := '1';
				count := 0;
			else
				interrupt := '0';
				count := count + 1;
			end if;
		end if;
		interrupt_o <= interrupt;
	end if;
end process;

end Behavioral;