library ieee;              -- Load the ieee 1164 library
use ieee.std_logic_1164.all;  -- Make the package 'visible'


-- The top level entity of the test bench has no ports...
entity adder4bit_slow_tb is
end adder4bit_slow_tb;

architecture stimulus of adder4bit_slow_tb is
  -- First, declare the lower-level entity...
  component adder4bit_slow
    port(a ,b : in std_logic_vector(3 downto 0);
        c_in: in std_logic;
        s : out std_logic_vector(3 downto 0);
        c_out : out std_logic);
  end component;

  -- Next, declare some local signals to assign values to AN observe...
  -- adder4bit_slow input
  signal a ,b : std_logic_vector(3 downto 0);
  signal c_in : std_logic;

  -- adder4bit_slow outputss
  signal s : std_logic_vector(3 downto 0);
  signal c_out : std_logic;


begin
  -- Create an instance of the component under test
  adder4bit_slow_instance: adder4bit_slow port map( a => a, b => b, c_in => c_in, s => s, c_out => c_out);

  -- Now define a process to apply some stimulus over time...
  process
    constant PERIOD: time := 40 ns;
  begin

    avector : for a4 in 0 to 15 loop
        if (a4 = 15) then
            a <= X"F";
        else if (a4 = 14) then
            a <= X"E";
        else if (a4 = 13) then
            a <= X"D";
        else if (a4 = 12) then
            a <= X"C";
        else if (a4 = 11) then
            a <= X"B";
        else if (a4 = 10) then
            a <= X"A";
        else if (a4 = 9) then
            a <= X"9";
        else if (a4 = 8) then
            a <= X"8";
        else if (a4 = 7) then
            a <= X"7";
        else if (a4 = 6) then
            a <= X"6";
        else if (a4 = 5) then
            a <= X"5";
        else if (a4 = 4) then
            a <= X"4";
        else if (a4 = 3) then
            a <= X"3";
        else if (a4 = 2) then
            a <= X"2";
        else if (a4 = 1) then
            a <= X"1";
        else if (a4 = 0) then
            a <= X"0";
        end if;
        wait for PERIOD;
    end loop avector;

    -- put breakpoint to line below
    wait for PERIOD;

    -- do not run again
    wait;
  end process;
end stimulus;