--另外，行為級的描述常常被用來產生仿真時的測試向量（testbench）文件。
--例如對于本節開始處提到的LED譯碼電路，可以編寫如下測試向量文件。
LIBRARY ieee;    
USE ieee.std_logic_1164.all;                                

ENTITY bin27seg_vhd_vec_tst IS
END bin27seg_vhd_vec_tst;
ARCHITECTURE bin27seg_arch OF bin27seg_vhd_vec_tst IS
-- constants                                                 
-- signals                                                   
	SIGNAL t_sig_data_in  : STD_LOGIC_VECTOR(3 DOWNTO 0);
	SIGNAL t_sig_data_out : STD_LOGIC_VECTOR(6 DOWNTO 0);
	SIGNAL t_sig_EN 	  : STD_LOGIC;
	COMPONENT bin27seg
		PORT (
				data_in  : IN STD_LOGIC_VECTOR(3 DOWNTO 0);
				data_out : OUT STD_LOGIC_VECTOR(6 DOWNTO 0);
				EN 		 : IN STD_LOGIC
		);
	END COMPONENT;
BEGIN
	tb : bin27seg
	PORT MAP (
				-- list connections between master ports and signals
					data_in 	=> t_sig_data_in,
					data_out 	=> t_sig_data_out,
					EN 			=> t_sig_EN
				);

-- data_in[3]
t_prcs_data_in_3: PROCESS
						BEGIN
							t_sig_data_in(3) <= '0';
							WAIT FOR 300000 ps;
							t_sig_data_in(3) <= '1';
							WAIT FOR 295000 ps;
							t_sig_data_in(3) <= '0';
							WAIT FOR 145000 ps;
							t_sig_data_in(3) <= '1';
						WAIT;
						END PROCESS t_prcs_data_in_3;

-- data_in[2]
t_prcs_data_in_2: PROCESS
						BEGIN
							t_sig_data_in(2) <= '0';
							WAIT FOR 595000 ps;
							t_sig_data_in(2) <= '1';
							WAIT FOR 280000 ps;
							t_sig_data_in(2) <= '0';
						WAIT;
						END PROCESS t_prcs_data_in_2;

-- data_in[1]
t_prcs_data_in_1: PROCESS
						BEGIN
							t_sig_data_in(1) <= '0';
							WAIT FOR 455000 ps;
							t_sig_data_in(1) <= '1';
							WAIT FOR 140000 ps;
							t_sig_data_in(1) <= '0';
							WAIT FOR 145000 ps;
							t_sig_data_in(1) <= '1';
							WAIT FOR 135000 ps;
							t_sig_data_in(1) <= '0';
						WAIT;
						END PROCESS t_prcs_data_in_1;
						
-- data_in[0]
t_prcs_data_in_0: PROCESS
						BEGIN
							t_sig_data_in(0) <= '0';
							WAIT FOR 165000 ps;
							t_sig_data_in(0) <= '1';
							WAIT FOR 135000 ps;
							t_sig_data_in(0) <= '0';
							WAIT FOR 295000 ps;
							t_sig_data_in(0) <= '1';
						WAIT;
						END PROCESS t_prcs_data_in_0;

-- EN
t_prcs_EN: PROCESS
			BEGIN
				t_sig_EN <= '0';
				WAIT FOR 75000 ps;
				t_sig_EN <= '1';
			WAIT;
			END PROCESS t_prcs_EN;
			
END bin27seg_arch;