LIBRARY ieee;
USE ieee.std_logic_1164.all;
ENTITY talu IS
END talu;

ARCHITECTURE one OF talu IS
  --declare and configure the mbalu here



  -- 
  --Signals to hook up the alu
  SIGNAL a,b,res : std_logic_vector(7 downto 0);
  SIGNAL addsub,cin,arlo : std_logic;  -- inputs
  SIGNAL csel : std_logic_vector(1 downto 0); -- input
  SIGNAL func : std_logic_vector(3 downto 0); -- input
  SIGNAL cout,n,z : std_logic; -- output signals
  SIGNAL err : std_logic;



BEGIN
  -- instantiate the DUT - the mbalu

  --Generate the stimulus  -- res and cout value is auto checked--DO N and V visually
  PROCESS
  BEGIN
    --initailize things
    a <= "00000000"; b<="00000000"; addsub<='1'; cin<='0'; csel<="00"; arlo<='0';
    err <= '0';  func<="1000";
    WAIT FOR 10 ns;
    --start with logic operations
    func<="1000"; -- AND function
    a <= "00000000"; b<="00000000";
    WAIT FOR 5 ns;
    IF (res /= "00000000") THEN err<='1'; END IF;
    WAIT FOR 1 ns;
    err<='0';
    WAIT FOR 4 ns;
    --next
    a <= "11111111"; b<="00000000";
    WAIT FOR 5 ns;
    IF (res /= "00000000") THEN err<='1'; END IF;
    WAIT FOR 1 ns;
    err<='0';
    WAIT FOR 4 ns;
    --next  
    a <= "11111111"; b<="01010101";
    WAIT FOR 5 ns;
    IF (res /= "01010101") THEN err<='1'; END IF;
    WAIT FOR 1 ns;
    err<='0';
    WAIT FOR 4 ns;
    --next
    func<="1110"; -- OR function
    a <= "00000000"; b<="00000000";
    WAIT FOR 5 ns;
    IF (res /= "00000000") THEN err<='1'; END IF;
    WAIT FOR 1 ns;
    err<='0';
    WAIT FOR 4 ns;
    --next
    a <= "11111111"; b<="00000000";
    WAIT FOR 5 ns;
    IF (res /= "11111111") THEN err<='1'; END IF;
    WAIT FOR 1 ns;
    err<='0';
    WAIT FOR 4 ns;
    --next  
    a <= "11111111"; b<="01010101";
    WAIT FOR 5 ns;
    IF (res /= "11111111") THEN err<='1'; END IF;
    WAIT FOR 1 ns;
    err<='0';
    WAIT FOR 4 ns;
    --START ARITH
    -- a+b+cin   where cin=0
    arlo<='1'; cin<='0'; csel<="00"; addsub<='1';
    a <= "11111111"; b<="00000000";
    WAIT FOR 5 ns;
    IF (res /= "11111111") THEN err<='1'; END IF;
    IF (cout /= '0')THEN err<='1'; END IF;
    WAIT FOR 1 ns;
    err<='0';
    WAIT FOR 4 ns;
    -- a+b+1
    arlo<='1'; cin<='0'; csel<="11"; addsub<='1';
    a <= "11111111"; b<="00000000";
    WAIT FOR 5 ns;
    IF (res /= "00000000") THEN err<='1'; END IF;
    IF (cout /= '1')THEN err<='1'; END IF;
    WAIT FOR 1 ns;
    err<='0';
    WAIT FOR 4 ns;
    -- a+b+cin where cin is 1
    arlo<='1'; cin<='1'; csel<="00"; addsub<='1';
    a <= "11111111"; b<="00000000";
    WAIT FOR 5 ns;
    IF (res /= "00000000") THEN err<='1'; END IF;
    IF (cout /= '1')THEN err<='1'; END IF;
    WAIT FOR 1 ns;
    err<='0';
    WAIT FOR 4 ns;
    -- a-b  with no carry in use
    arlo<='1'; cin<='0'; csel<="11"; addsub<='0';
    a <= "11111111"; b<="00000000";
    WAIT FOR 5 ns;
    IF (res /= "11111111") THEN err<='1'; END IF;
    IF (cout /= '1')THEN err<='1'; END IF;
    WAIT FOR 1 ns;
    err<='0';
    WAIT FOR 4 ns;
    -- a+b-cin
    arlo<='1'; cin<='0'; csel<="01"; addsub<='1';
    a <= "11110001"; b<="00000011";
    WAIT FOR 5 ns;
    IF (res /= "11101110") THEN err<='1'; END IF;
    IF (cout /= '1')THEN err<='1'; END IF;
    WAIT FOR 1 ns;
    err<='0';
    WAIT FOR 4 ns;
-- You can add more tests if you like
-- Note that N and Z are not tested for  -- DO THAT VISUALLY
  WAIT FOR 20 ns;
  WAIT;
  END PROCESS;
  
END one;