alu

library ieee;
use ieee.std_logic_1164.all;
use ieee.numeric_std.all;
entity Projekt is
port (    A : in signed(15 downto 0);
B : in signed(15 downto 0);
Salu : in bit_vector (3 downto 0);
LDF : in bit;
 clk : in bit;
Y : out signed (15 downto 0);
C,Z,S : out std_logic
);
end entity;
architecture rtl of Projekt is
   begin
process (Salu, A, B, clk)
variable res, AA, BB,CC: signed (16 downto 0);
variable CF,ZF,SF : std_logic;
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 := BB;
when "0010" => res := AA + BB;
when "0011" => res := AA - BB;
when "1111" => res(16) := AA(16);
when others => res := AA;
res(15 downto 0) := AA(16 downto 1);
end case;
Y <= res(15 downto 0);
Z <= ZF;
S <= SF;
C <= CF;
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;