-- dowload from: www.fpga.com.cn & www.pld.com.cn


LIBRARY IEEE;
USE IEEE.std_logic_1164.ALL;
USE IEEE.std_logic_unsigned.ALL;
USE IEEE.std_logic_arith.ALL;

ENTITY step_motor IS
	PORT(
		f, p, d: IN	STD_LOGIC:='0';
		speed : in  STD_LOGIC_VECTOR(1 downto 0);	
		coil : OUT	STD_LOGIC_VECTOR(3 downto 0)
         );
		
END step_motor;
ARCHITECTURE behavior OF step_motor IS
	SIGNAL ind_coil: STD_LOGIC_VECTOR(3 downto 0) := "0001";
	SIGNAL clk_scan: STD_LOGIC;
    SIGNAL PHASE,DIRECTION:STD_LOGIC;
    signal t:std_logic_vector(3 downto 0);
	signal comp:integer range 0 to 2500 ;
    SIGNAL osc:STD_LOGIC;
     BEGIN
coil <= t;

process(f,osc)
variable delay:integer range 0 to 50;
begin
if (f'event and f='1') then
 if delay>=50 then delay:=0;osc<=not osc;
 else delay:=delay+1;
end if;
end if;

if (osc'event and osc='1') then 
case speed is

   when "10" => if comp<2500 then comp<=comp+1; 
                else comp<=comp; 
                end if;
   when "01" => if comp>2 then comp<=comp-1;
                else comp<=comp;
                end if;
   when others => if comp<2 then comp<=2;
                else comp<=comp;
                end if;
end case;
end if;
end process;


PROCESS
	VARIABLE d_ff: integer range 0 to 2500;
	
BEGIN

	WAIT UNTIL f = '1';
	if d_ff >= comp then
		d_ff :=0; clk_scan <= not CLK_SCAN;
	else
		d_ff := d_ff + 1;
	end if;
	   	END PROCESS ;
 
 PROCESS(F)
 VARIABLE B:STD_LOGIC;
 BEGIN
 IF (F'EVENT AND F='1') THEN B:=(P and (b and P) );
 IF B='1' THEN PHASE<=NOT PHASE ;B:='0';
 ELSIF P='0' THEN PHASE<=PHASE;B:='1';
 END IF;
 END IF;
 END PROCESS;

 PROCESS(F)
 VARIABLE B:STD_LOGIC;
 BEGIN
 IF (F'EVENT AND F='1') THEN B:=(D and (b and D) );
 IF B='1' THEN DIRECTION<=NOT DIRECTION ;B:='0';
 ELSIF D='0' THEN DIRECTION<=DIRECTION;B:='1';
 END IF;
 END IF;
 END PROCESS;

motor:
process
begin
--if (clk_scan'event and clk_scan='1') then
WAIT UNTIL clk_scan= '0';
	CASE phase IS
		WHEN '1' =>
		    IF direction = '0' THEN
		        IF ((ind_coil = "1001") or (ind_coil = "0000")) THEN
		         	ind_coil <= "0001";
		        ELSE
		         	ind_coil <= (ind_coil(2 downto 0) & ind_coil(3));
	        	END IF;
		    ELSE
		        IF ((ind_coil = "1001") or (ind_coil = "0000")) THEN
		        	ind_coil <= "1000";
		        ELSE
		         	ind_coil <= (ind_coil(0) & ind_coil(3 downto 1));
	        	END IF;
		    END IF;
					

           WHEN OTHERS => 
                         ind_coil<=IND_COIL;
           END CASE;
t<=not ind_coil;
END PROCESS motor;

END behavior;