ENTITY tfa IS
END tfa;

ARCHITECTURE one OF tfa IS
-- declare component to be tested
  COMPONENT fa8 IS
    PORT(a,b : IN BIT_VECTOR(7 downto 0);
         cin : IN BIT;
         sum : OUT BIT_VECTOR(7 downto 0);
         cout : OUT BIT);
  END COMPONENT;
  FOR rip : fa8 USE ENTITY work.fa8(one);
  FOR cs  : fa8 USE ENTITY work.fa8(two);
  SIGNAL a,b,sumrip,sumcs : BIT_VECTOR(7 downto 0);
  SIGNAL cin,coutrip,coutcs : BIT;

BEGIN
  rip : fa8 PORT MAP (a,b,cin,sumrip,coutrip);
  cs  : fa8 PORT MAP (a,b,cin,sumcs,coutcs);

PROCESS --apply stimulus to the adders
BEGIN
  cin <= '0';
  -- start a and b input sequence for cin of '0'
  a <= "00000000";
  b <= "00000000";
  WAIT FOR 25 ns;
  b <= "11111111";
  WAIT FOR 25 ns;
  b <= "01010101";
  WAIT FOR 25 ns;
  b <= "10101010";
  WAIT FOR 25 ns;
  b <= "01110111";
  WAIT FOR 25 ns;
  b <= "10001000";
  WAIT FOR 25 ns;
  --move to next a
  a <= "11111111";
  b <= "00000000";
  WAIT FOR 25 ns;
  b <= "11111111";
  WAIT FOR 25 ns;
  b <= "01010101";
  WAIT FOR 25 ns;
  b <= "10101010";
  WAIT FOR 25 ns;
  b <= "01110111";
  WAIT FOR 25 ns;
  b <= "10001000";
  WAIT FOR 25 ns;
  --move to next a
  a <= "01010101";
  b <= "00000000";
  WAIT FOR 25 ns;
  b <= "11111111";
  WAIT FOR 25 ns;
  b <= "01010101";
  WAIT FOR 25 ns;
  b <= "10101010";
  WAIT FOR 25 ns;
  b <= "01110111";
  WAIT FOR 25 ns;
  b <= "10001000";
  WAIT FOR 25 ns;
  --move to next a
  a <= "10101010";
  b <= "00000000";
  WAIT FOR 25 ns;
  b <= "11111111";
  WAIT FOR 25 ns;
  b <= "01010101";
  WAIT FOR 25 ns;
  b <= "10101010";
  WAIT FOR 25 ns;
  b <= "01110111";
  WAIT FOR 25 ns;
  b <= "10001000";
  WAIT FOR 25 ns;
  --move to next a
  a <= "11101110";
  b <= "00000000";
  WAIT FOR 25 ns;
  b <= "11111111";
  WAIT FOR 25 ns;
  b <= "01010101";
  WAIT FOR 25 ns;
  b <= "10101010";
  WAIT FOR 25 ns;
  b <= "01110111";
  WAIT FOR 25 ns;
  b <= "10001000";
  WAIT FOR 25 ns;
  --move to next a
  a <= "01110111";
  b <= "00000000";
  WAIT FOR 25 ns;
  b <= "11111111";
  WAIT FOR 25 ns;
  b <= "01010101";
  WAIT FOR 25 ns;
  b <= "10101010";
  WAIT FOR 25 ns;
  b <= "01110111";
  WAIT FOR 25 ns;
  b <= "10001000";
  WAIT FOR 25 ns;
  -- then repeat for cin of '1'
  cin <= '1';
  a <= "00000000";
  b <= "00000000";
  WAIT FOR 25 ns;
  b <= "11111111";
  WAIT FOR 25 ns;
  b <= "01010101";
  WAIT FOR 25 ns;
  b <= "10101010";
  WAIT FOR 25 ns;
  b <= "01110111";
  WAIT FOR 25 ns;
  b <= "10001000";
  WAIT FOR 25 ns;
  --move to next a
  a <= "11111111";
  b <= "00000000";
  WAIT FOR 25 ns;
  b <= "11111111";
  WAIT FOR 25 ns;
  b <= "01010101";
  WAIT FOR 25 ns;
  b <= "10101010";
  WAIT FOR 25 ns;
  b <= "01110111";
  WAIT FOR 25 ns;
  b <= "10001000";
  WAIT FOR 25 ns;
  --move to next a
  a <= "01010101";
  b <= "00000000";
  WAIT FOR 25 ns;
  b <= "11111111";
  WAIT FOR 25 ns;
  b <= "01010101";
  WAIT FOR 25 ns;
  b <= "10101010";
  WAIT FOR 25 ns;
  b <= "01110111";
  WAIT FOR 25 ns;
  b <= "10001000";
  WAIT FOR 25 ns;
  --move to next a
  a <= "10101010";
  b <= "00000000";
  WAIT FOR 25 ns;
  b <= "11111111";
  WAIT FOR 25 ns;
  b <= "01010101";
  WAIT FOR 25 ns;
  b <= "10101010";
  WAIT FOR 25 ns;
  b <= "01110111";
  WAIT FOR 25 ns;
  b <= "10001000";
  WAIT FOR 25 ns;
  --move to next a
  a <= "11101110";
  b <= "00000000";
  WAIT FOR 25 ns;
  b <= "11111111";
  WAIT FOR 25 ns;
  b <= "01010101";
  WAIT FOR 25 ns;
  b <= "10101010";
  WAIT FOR 25 ns;
  b <= "01110111";
  WAIT FOR 25 ns;
  b <= "10001000";
  WAIT FOR 25 ns;
  --move to next a
  a <= "01110111";
  b <= "00000000";
  WAIT FOR 25 ns;
  b <= "11111111";
  WAIT FOR 25 ns;
  b <= "01010101";
  WAIT FOR 25 ns;
  b <= "10101010";
  WAIT FOR 25 ns;
  b <= "01110111";
  WAIT FOR 25 ns;
  b <= "10001000";
  WAIT FOR 25 ns;
  WAIT;
END PROCESS;
END one;