-- file "rotater.vhd"
-----------------------------------------------------------------------
-- counts a specified number of clock pulses from a trigger
-- used to control the stepper motor rotation
-- written by Shaun Luong, Clifton Yeung, Jon Paul Kansky
-- and Patrick Asiedu-Ampem, University of Alberta
-- November 1998
-----------------------------------------------------------------------

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

entity rotater is
	generic(pulse_num: positive:= 10);	-- change this for
										-- different # clock pulses
	port
	(
		clock, reset: in std_logic;
		start: in std_logic;
		rot_enable: out std_logic;
		stop: out std_logic
	);
end rotater;

architecture counting of rotater is

begin

	process(reset, clock)

		variable stepper: integer;		-- intermediate count
		variable count: boolean;

	begin

		if reset = '1' then				-- active low
			count := false;
			stepper := 0;
			rot_enable <= '0';
			stop <= '0';
		elsif rising_edge(clock) then
			if start = '1' then
				count := true;
			else
				count := false;
			end if;
			if count = true then
				if stepper < pulse_num then
					rot_enable <= '1';			-- enable motor rotation
					stepper := stepper + 1;		-- increment count
				elsif stepper >= pulse_num then
					rot_enable <= '0';			-- disable motor rotation
					stop <= '1';				-- done counting
				end if;		
			end if;	
		end if;

	end process;

end counting;