entity b14_1 is
port (
	clock,reset : in bit;
	addr : out integer range 2**20 - 1 downto 0;
	datai : in integer;
	datao : out integer;
	rd,wr : out bit
	);
end b14_1;

architecture BEHAV of b14_1 is

begin 

process(clock,reset)

variable reg0 : integer;
variable reg1 : integer;
variable reg2 : integer;
variable reg3 : integer;

variable B : bit;

variable MAR : integer range 2**20 - 1 downto 0;
variable MBR : integer;

variable mf : integer range 2**2 - 1 downto 0;
variable df : integer range 2**3 - 1 downto 0;
variable cf : integer range 1 downto 0;

variable ff : integer range 2**4 - 1 downto 0;
variable tail : integer range 2**20 - 1 downto 0;
variable IR : integer;

variable state : integer range 1 downto 0;

variable r,m,t: integer;
variable d : integer;
variable temp : integer;
variable s : integer range 3 downto 0;

constant FETCH : integer := 0;
constant EXEC : integer :=1;

begin

  if reset = '1' then
      MAR := 0;
      MBR := 0;
      IR := 0;
      d := 0;
      r := 0;
      m := 0;
      s := 0;
      temp := 0;
      mf := 0;
      df := 0;
      ff := 0;
      cf := 0;
      tail := 0;
      b := '0';
      reg0 := 0;
      reg1 := 0;
      reg2 := 0;
      reg3 := 0;
      addr <= 0;
      rd <= '0';
      wr <= '0';
      datao <= 0;
      state := FETCH;
 elsif clock'event and clock='1' then
      rd <= '0';
      wr <= '0';
      case state is
      when FETCH =>
        MAR := reg3 mod 2**20;
	addr <= MAR;
	rd <= '1';
	MBR := datai;
        IR := MBR;
	state := EXEC;
      when EXEC =>
	if IR<0 then
	  IR := -IR;
	end if;
	mf := (IR / 2**27) mod 4 ;

	df := (IR / 2**24) mod 2**3;

	ff := (IR / 2**20) mod 2**4;

	cf := (IR / 2**23) mod 2;

	tail := IR mod 2**20;
        reg3 := ((reg3 mod 2**29)+ 8);
	s := (IR/2**29) mod 4;
	case s is
	when 0 => r := reg0;
	when 1 => r := reg1;
	when 2 => r := reg2;
	when 3 => r := reg3;
	end case;
	case cf is
	when 1 =>
	  case mf is
	  when 0 => m := tail;
	  when 1 => m := datai;
		addr <= tail;
		rd <= '1';
	  when 2 => addr <= (tail + reg1) mod 2**20;
		rd <= '1';
                m := datai;
	  when 3 => addr <= (tail + reg2) mod 2**20;
		rd <= '1';
                m := datai;
	  end case;
	  case ff is
	  when 0 => if r < m then
                   B := '1';
                  else
                   B := '0';
                  end if;
	  when 1 => if not(r < m) then 
                   B := '1';
                  else
                   B := '0'; 
                  end if;
	  when 2 => if r = m then 
                   B := '1';
                  else 
                   B := '0'; 
                  end if;  
	  when 3 => if not(r = m) then 
                   B := '1'; 
                  else
                   B := '0';
                  end if; 
	  when 4 => if not(r > m) then
                   B := '1'; 
                  else 
                   B := '0'; 
                  end if;
	  when 5 => if r > m then 
                   B := '1'; 
                  else 
                   B := '0'; 
                  end if;
	  when 6 => if r > 2**30 - 1 then
                   r := r - 2**30;
                  end if;
		  if r < m then 
                   B := '1'; 
                  else 
                   B := '0'; 
                  end if;
	  when 7 => if r > 2**30 - 1 then
                   r := r - 2**30;
                  end if;
		  if not(r < m) then
                   B := '1'; 
                  else 
                   B := '0'; 
                  end if; 
	  when 8 => if (r < m) or ( B = '1') then
                    B := '1';
                   else
                    B := '0';
                   end if;
	  when 9 => if not(r < m) or ( B = '1') then
                    B := '1';
                   else
                    B := '0';
                   end if;
	  when 10 => if (r = m) or ( B = '1') then
                    B := '1';
                   else
                    B := '0';
                   end if;
	  when 11 => if not(r = m) or ( B = '1') then
                    B := '1';
                   else
                    B := '0';
                   end if;
	  when 12 => if not(r > m) or (B = '1') then
                    B := '1';
                   else
                    B := '0';
                   end if;
	  when 13 => if (r > m) or (B = '1') then
                    B := '1';
                   else
                    B := '0';
                   end if;
	  when 14 => if r > 2**30 - 1 then
                   r := r - 2**30;
                  end if;
		   if (r < m) or ( B = '1') then
                    B := '1';              
                   else
                    B := '0';
                   end if;
	  when 15 => if r > 2**30 - 1 then
                   r := r - 2**30;
                  end if;
	           if not(r < m) or ( B = '1') then
                    B := '1';
                   else
                    B := '0';
                   end if;
	  end case;
	when 0 =>
	    if not(df = 7) then
	        if df = 5 then 
	          if not(B) = '1' then
	            d := 3;
	          end if;
	        elsif df = 4 then
	          if B = '1' then
	            d := 3;
	          end if;
	        elsif df = 3 then
	          d := 3;
	        elsif df = 2 then d := 2;
	        elsif df = 1 then d := 1;
	        elsif df = 0 then d := 0;
	        end if;
	    case ff is
	    when 0 =>  
	      case mf is
	      when 0 => m := tail;
	      when 1 => m := datai;
		addr <= tail;
		rd <= '1';
	      when 2 => addr <= (tail + reg1) mod 2**20;
		rd <= '1';
                m := datai;
	      when 3 => addr <= (tail + reg2) mod 2**20;
		rd <= '1';
                m := datai;
	      end case;
	      t := 0;
	      case d is
	      when 0 => reg0 := t - m;
	      when 1 => reg1 := t - m;
	      when 2 => reg2 := t - m;
	      when 3 => reg3 := t - m;
	      when others => null;
	      end case;
	    when 1 =>  
	      case mf is
	      when 0 => m := tail;
	      when 1 => m := datai;
		addr <= tail;
		rd <= '1';
	      when 2 => addr <= (tail + reg1) mod 2**20;
		rd <= '1';
                m := datai;
	      when 3 => addr <= (tail + reg2) mod 2**20;
		rd <= '1';
                m := datai;
	      end case;
	      reg2 := reg3; 
	      reg3 := m;
	    when 2 =>  
	      case mf is
	      when 0 => m := tail;
	      when 1 => m := datai;
		addr <= tail;
		rd <= '1';
	      when 2 => addr <= (tail + reg1) mod 2**20;
		rd <= '1';
                m := datai;
	      when 3 => addr <= (tail + reg2) mod 2**20;
		rd <= '1';
                m := datai;
	      end case;
	      case d is
	      when 0 => reg0 := m;
	      when 1 => reg1 := m;
	      when 2 => reg2 := m;
	      when 3 => reg3 := m;
	      when others => null;
	      end case;
	    when 3 =>  
	      case mf is
	      when 0 => m := tail;
	      when 1 => m := datai;
		addr <= tail;
		rd <= '1';
	      when 2 => addr <= (tail + reg1) mod 2**20;
		rd <= '1';
                m := datai;
	      when 3 => addr <= (tail + reg2) mod 2**20;
		rd <= '1';
                m := datai;
	      end case;
	      case d is
	      when 0 => reg0 := m;
	      when 1 => reg1 := m;
	      when 2 => reg2 := m;
	      when 3 => reg3 := m;
	      when others => null;
	      end case;
	    when 4 =>  
	      case mf is
	      when 0 => m := tail;
	      when 1 => m := datai;
		addr <= tail;
		rd <= '1';
	      when 2 => addr <= (tail + reg1) mod 2**20;
		rd <= '1';
                m := datai;
	      when 3 => addr <= (tail + reg2) mod 2**20;
		rd <= '1';
                m := datai;
	      end case;
	      case d is
	      when 0 => reg0 := (r + m) mod 2**30;
	      when 1 => reg1 := (r + m) mod 2**30;
	      when 2 => reg2 := (r + m) mod 2**30;
	      when 3 => reg3 := (r + m) mod 2**30;
	      when others => null;
	      end case;
	    when 5 =>  
	      case mf is
	      when 0 => m := tail;
	      when 1 => m := datai;
		addr <= tail;
		rd <= '1';
	      when 2 => addr <= (tail + reg1) mod 2**20;
		rd <= '1';
                m := datai;
	      when 3 => addr <= (tail + reg2) mod 2**20;
		rd <= '1';
                m := datai;
	      end case;
	      case d is
	      when 0 => reg0 := (r + m) mod 2**30;
	      when 1 => reg1 := (r + m) mod 2**30;
	      when 2 => reg2 := (r + m) mod 2**30;
	      when 3 => reg3 := (r + m) mod 2**30;
	      when others => null;
	      end case;
	    when 6 =>   
	      case mf is
	      when 0 => m := tail;
	      when 1 => m := datai;
		addr <= tail;
		rd <= '1';
	      when 2 => addr <= (tail + reg1) mod 2**20;
		rd <= '1';
                m := datai;
	      when 3 => addr <= (tail + reg2) mod 2**20;
		rd <= '1';
                m := datai;
	      end case;
	      case d is
	      when 0 => reg0 := (r - m) mod 2**30;
	      when 1 => reg1 := (r - m) mod 2**30;
	      when 2 => reg2 := (r - m) mod 2**30;
	      when 3 => reg3 := (r - m) mod 2**30;
	      when others => null;
	      end case;
	    when 7 =>  
	      case mf is
	      when 0 => m := tail;
	      when 1 => m := datai;
		addr <= tail;
		rd <= '1';
	      when 2 => addr <= (tail + reg1) mod 2**20;
		rd <= '1';
                m := datai;
	      when 3 => addr <= (tail + reg2) mod 2**20;
		rd <= '1';
                m := datai;
	      end case;
	      case d is
	      when 0 => reg0 := (r - m) mod 2**30;
	      when 1 => reg1 := (r - m) mod 2**30;
	      when 2 => reg2 := (r - m) mod 2**30;
	      when 3 => reg3 := (r - m) mod 2**30;
	      when others => null;
	      end case;
	    when 8 =>  
	      case mf is
	      when 0 => m := tail;
	      when 1 => m := datai;
		addr <= tail;
		rd <= '1';
	      when 2 => addr <= (tail + reg1) mod 2**20;
		rd <= '1';
                m := datai;
	      when 3 => addr <= (tail + reg2) mod 2**20;
		rd <= '1';
                m := datai;
	      end case;
	      case d is
	      when 0 => reg0 := (r + m) mod 2**30;
	      when 1 => reg1 := (r + m) mod 2**30;
	      when 2 => reg2 := (r + m) mod 2**30;
	      when 3 => reg3 := (r + m) mod 2**30;
	      when others => null;
	      end case;
	    when 9 =>  
	      case mf is
	      when 0 => m := tail;
	      when 1 => m := datai;
		addr <= tail;
		rd <= '1';
	      when 2 => addr <= (tail + reg1) mod 2**20;
		rd <= '1';
                m := datai;
	      when 3 => addr <= (tail + reg2) mod 2**20;
		rd <= '1';
                m := datai;
	      end case;
	      case d is
	      when 0 => reg0 := (r - m) mod 2**30;
	      when 1 => reg1 := (r - m) mod 2**30;
	      when 2 => reg2 := (r - m) mod 2**30;
	      when 3 => reg3 := (r - m) mod 2**30;
	      when others => null;
	      end case;
	    when 10 =>  
	      case mf is
	      when 0 => m := tail;
	      when 1 => m := datai;
		addr <= tail;
		rd <= '1';
	      when 2 => addr <= (tail + reg1) mod 2**20;
		rd <= '1';
                m := datai;
	      when 3 => addr <= (tail + reg2) mod 2**20;
		rd <= '1';
                m := datai;
	      end case;
	      case d is
	      when 0 => reg0 := (r + m) mod 2**30;
	      when 1 => reg1 := (r + m) mod 2**30;
	      when 2 => reg2 := (r + m) mod 2**30;
	      when 3 => reg3 := (r + m) mod 2**30;
	      when others => null;
	      end case;
	    when 11 =>  
	      case mf is
	      when 0 => m := tail;
	      when 1 => m := datai;
		addr <= tail;
		rd <= '1';
	      when 2 => addr <= (tail + reg1) mod 2**20;
		rd <= '1';
                m := datai;
	      when 3 => addr <= (tail + reg2) mod 2**20;
		rd <= '1';
                m := datai;
	      end case;
	      case d is
	      when 0 => reg0 := (r - m) mod 2**30;
	      when 1 => reg1 := (r - m) mod 2**30;
	      when 2 => reg2 := (r - m) mod 2**30;
	      when 3 => reg3 := (r - m) mod 2**30;
	      when others => null;
	      end case;
	    when 12 =>
	      case mf is
	      when 0 => t := r / 2;
              when 1 => t := r / 2;
		if B = '1' then
		  t := t mod  2**29;
		end if;
	      when 2 => t := (r mod 2**29) * 2;
	      when 3 => t := (r mod 2**29) * 2;
		if t > 2**30 - 1 then
		  B := '1';
		else
		  B := '0';
		end if;
              when others => null;
	      end case;
	      case d is
	      when 0 => reg0 := t;
	      when 1 => reg1 := t;
	      when 2 => reg2 := t;
	      when 3 => reg3 := t;
	      when others => null;
	      end case;
	    when 13 | 14 | 15 => null;
	    end case;
	  elsif df = 7 then
	    case mf is
	    when 0 => m := tail;
	    when 1 => m := tail;
	    when 2 => m := (reg1 mod 2**20) + (tail mod 2**20);
	    when 3 => m := (reg2 mod 2**20) + (tail mod 2**20);
	    end case;
	    -- addr <= m;
	    addr <= m mod 2**20;
	    -- removed (!)fs28032001
	    wr <='1';
	    datao <= r;
	  end if;
	end case;
	state := FETCH;
      end case;
  end if;

end process;

end BEHAV;