-------------------------------------
--	mult_control.vhd
--	Multiplier Controller
--
--	February 26, 2000
--	Ross, Daniel 355951
--
--	This entity controls the
--	signed integer multiplier
--	entity.

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

entity mult_control is
		port (resetin, clock, done, control_bit: in std_logic;
		loadG,loadP,loadQ,loadR: out std_logic;
		resetG,resetP,resetQ,resetR,reset_counter: out std_logic;
		count,shift: out std_logic
		);
end mult_control;	

architecture behavioral of mult_control is

-- Finite state machine states
type states is (idle, initialize, add, shiftcount);
signal current_state, next_state : states;

begin

combinational_logic : process (current_state, next_state, resetin, clock, done, control_bit)

begin

case current_state is
	when idle =>
		-- nothing happens here.
		
		loadG <= '0';
		loadP <= '0';
		loadQ <= '0';
		loadR <= '0';	
		resetG <= '0';
		resetP <= '0';
		resetQ <= '0';
		resetR <= '0';
		reset_counter <= '0';
		count <= '0';
		shift <= '0';
						
		-- next state
		if resetin = '1' then
			next_state <= initialize;
		else
			next_state <= idle;
		end if;
		
	when initialize =>
		-- we will reset Registers G and P, and load Q and R.
		-- we will also reset our counter and adder.
		
		loadG <= '0';
		loadP <= '0';
		loadQ <= '1';
		loadR <= '1';	
		resetG <= '1';
		resetP <= '1';
		resetQ <= '0';
		resetR <= '0';
		reset_counter <= '1';
		count <= '0';		
		shift <= '0';
		
		if resetin = '1' then
			next_state <= initialize;	
		elsif control_bit = '1' then
			next_state <= add;
		else
			next_state <= shiftcount;
		end if;

	when add =>
		-- The sum of R and P will go into P.
		
		loadG <= '0';
		loadP <= '1';
		loadQ <= '0';
		loadR <= '0';	
		resetG <= '0';
		resetP <= '0';
		resetQ <= '0';
		resetR <= '0';
		reset_counter <= '0';
		count <= '0';
		shift <= '0';
		
		if resetin = '1' then
			next_state <= initialize;
		else
			next_state <= shiftcount;
		end if;

	when shiftcount =>
		-- we will count up one and shift all our stuff.
		
		loadG <= '0';
		loadP <= '0';
		loadQ <= '0';
		loadR <= '0';	
		resetG <= '0';
		resetP <= '0';
		resetQ <= '0';
		resetR <= '0';
		reset_counter <= '0';
		count <= '1';
		shift <= '1';
		
		if resetin = '1' then
			next_state <= initialize;				
		elsif done = '1' then
			next_state <= idle;
		elsif control_bit = '1' then
			next_state <= add;
		else
			next_state <= shiftcount;
		end if;
end case;

end process combinational_logic;

state_register : process(resetin, clock, current_state) 
begin 
        if rising_edge(clock) then
		        -- advance to next state 
                current_state <= next_state;                
        end if; 
        
end process state_register; 


end behavioral;