library ieee;
use ieee.std_logic_1164.all;
use ieee.numeric_std.all;


entity projektASK is
    port (
            A : in signed(15 downto 0);
            B : in signed(15 downto 0);
            Salu : in signed(3 downto 0);
            LDF : in bit;
            clk : in std_logic;
            Y : out signed (15 downto 0);
            C,Z,S,P : out std_logic
            );
end entity;

architecture rtl of projektASK is
    begin
        process (Salu, A, B, clk)
            variable res, AA, BB,CC: signed (16 downto 0):= (others => '0');
            variable CF,ZF,SF,PF : std_logic:= '0';
            variable temp: signed (7 downto 0):= (others => '0');
            begin
            AA(16) := A(15);
            AA(15 downto 0) := A;
            BB(16) := B(15);
            BB(15 downto 0) := B;
            CC(0) := CF;
            CC(16 downto 1) := "0000000000000000";

            case Salu is
                when "0000" => res := AA;
                when "0001" => res := AA + BB;
                when "0010" => res := AA - BB;
                when "0011" => if(AA = BB) then AA := res;
                                                          BB := res;
                                    end if;
                when "0100" => if(AA >= BB) then AA := res;
                                                            BB := res;
                                    end if;
                when "0101" => if(AA > BB) then res :="00000000000000001";
                                    else res := "00000000000000000";
                                    end if;
                when "0110" => if(AA <= BB) then res :="00000000000000001";
                                    else res := "00000000000000000";
                                    end if;
                when "0111" => if(AA < BB) then res :="00000000000000001";
                                    else res := "00000000000000000";
                                    end if;
                when "1000" => AA :=  AA xor BB; -- or;
                when "1001" => AA := shift_left(signed(AA), to_integer(signed(BB)));
                when "1010" => AA := shift_right(signed(AA), to_integer(signed(BB)));
                when OTHERS => res(16) := AA(16);
                --res(15 downto 0) := AA(16 downto 1);
                res(15 downto 0) := AA(15 downto 0);
            end case;

            Y <= res(15 downto 0);
            Z <= ZF;
            S <= SF;
            C <= CF;
            P <= PF;
            if (clk'event and clk='1') then
                if (LDF='1') then
                    if (res = "00000000000000000") then
                    ZF:='1';
                    else ZF:='0';
                    end if;
                if (res(15)='1') then SF:='1';
                else SF:='0'; end if;
                CF := res(16) xor res(15);
                end if;
            end if;
        end process;
end rtl;