entity control is
    Port (          CLR : in std_logic;
                    CLK : in std_logic;
							MX : out std_logic_vector(2 downto 0);
                   CTRL : out std_logic;
		  LDA, LDB, LDACC : out std_logic);
end control;


architecture Behavioral of control is
	type state_type is (LDRA,LDRB,ADDA,SUBB,ADDB,INC,CLEAR);
	attribute ENUM_ENCODING: STRING;
--	attribute ENUM_ENCODING of state_type: type is "100000 010000 001000 000100 000010 000001";
	signal PS,NS : state_type;

begin

sync_proc: process (CLK,CLR,NS)
	begin
		if (CLR = '1') then PS <= CLEAR;									--the program is reset/stopped
		elsif (rising_edge(CLK)) then PS <= NS;
		end if;
end process sync_proc;

comb_proc: process (PS)
	begin
			case (PS) is
			when LDRA => 														--register a is loaded
						LDA <= '1';
						LDB <= '0';
						LDACC <= '0';
						MX <= "000";
						CTRL <= '0';
						NS <= LDRB;
			when LDRB =>														--register b is loaded
						LDA <= '0';
						LDB <= '1';
						LDACC <= '0';
						MX <= "000";
						CTRL <= '0';
						NS <= ADDA;
			when ADDA =>														--mux chosen to add A to the value in acc
						LDA <= '0';
						LDB <= '0';
						LDACC <= '1';
						MX <= "000";
						CTRL <= '0';
						NS <= SUBB;
			when SUBB =>														--mux chosen to subtract B to the value in acc
						LDA <= '0';
						LDB <= '0';
						LDACC <= '1';
						MX <= "011";											--not B
						CTRL <= '1';
						NS <= INC;
			when INC =>															--the value mux has chosen is zeros. incrementing by 1
						LDA <= '0';
						LDB <= '0';
						LDACC <= '1';
						MX <= "100";
						CTRL <= '1';
						NS <= ADDB;
			when ADDB =>														--mux chosen to add B to the value in acc
			         LDA <= '0';
						LDB <= '0';
						LDACC <= '1';
						MX <= "001";
						CTRL <= '0';
						NS <= LDRA;
			when CLEAR =>
						LDA <= '0';
						LDB <= '0';
						LDACC <= '0';
						MX <= "000";
						NS <= LDRA;
			when others =>														-- the just in case case...
						LDA <= '0';
						LDB <= '0';
						LDACC <= '0';
						MX <= "000";
						CTRL <= '0';
						NS <= LDRA;
		end case;
	end process comb_proc;
end Behavioral;