---------------------------------------------------------------
-- Test Bench for Multiplexer (ESD figure 2.5)
-- by Weijun Zhang, 04/2001
--
-- four operations are tested in this example.
---------------------------------------------------------------

library IEEE;
use IEEE.std_logic_1164.all;
use IEEE.std_logic_arith.all;

entity Mux_TB is			-- empty entity
end Mux_TB;

---------------------------------------------------------------

architecture TB of Mux_TB is

    -- initialize the declared signals  
    signal T_I3: std_logic_vector(2 downto 0):="000"; 
    signal T_I2: std_logic_vector(2 downto 0):="000";
    signal T_I1: std_logic_vector(2 downto 0):="000";
    signal T_I0: std_logic_vector(2 downto 0):="000";
    signal T_O: std_logic_vector(2 downto 0);
    signal T_S: std_logic_vector(1 downto 0);
	
    component Mux
    port(	I3: 	in std_logic_vector(2 downto 0);
		I2: 	in std_logic_vector(2 downto 0);
		I1: 	in std_logic_vector(2 downto 0);
		I0: 	in std_logic_vector(2 downto 0);
		S:	in std_logic_vector(1 downto 0);
		O:	out std_logic_vector(2 downto 0)
    );
    end component;

begin

    U_Mux: Mux port map (T_I3, T_I2, T_I1, T_I0, T_S, T_O);
	
    process							
	
	variable err_cnt: integer :=0;
	
    begin								
			 	
	T_I3 <= "001";		-- I0-I3 are different signals
	T_I2 <= "010";
	T_I1 <= "101";
	T_I0 <= "111";
		
	-- case select eqaul "00"
	wait for 10 ns;	
	T_S <= "00";	
	wait for 1 ns;
	assert (T_O="111") report "Error Case 0" severity error;
	if (T_O/="111") then 
	    err_cnt := err_cnt+1;
	end if;
		
	-- case select equal "01"
	wait for 10 ns;
	T_S <= "01";	  
	wait for 1 ns;
	assert (T_O="101") report "Error Case 1" severity error;
	if (T_O/="101") then 
	    err_cnt := err_cnt+1;
	end if;
		
	-- case select equal "10"
	wait for 10 ns;
	T_S <= "10";	  
	wait for 1 ns;
	assert (T_O="010") report "Error Case 2" severity error;
	if (T_O/="010") then 
	    err_cnt := err_cnt+1;
	end if;		
			
	-- case select equal "11"
	wait for 10 ns;
	T_S <= "11";	  
	wait for 1 ns;
	assert (T_O="001") report "Error Case 3" severity error;		
	if (T_O/="001") then 
	    err_cnt := err_cnt+1;
	end if;
			
	-- case equal "11"
	wait for 10 ns;
	T_S <= "UU";

	-- summary of all the tests
	if (err_cnt=0) then
	    assert (false) 
	    report "Testbench of Mux completed sucessfully!"
	    severity note;
	else
	    assert (true)
	    report "Something wrong, try again!"
	    severity error;
	end if;
		
	wait;
    
    end process;

end TB;

----------------------------------------------------------------
configuration CFG_TB of Mux_TB is
	for TB
	end for;
end CFG_TB;
-----------------------------------------------------------------