VHDL学习笔记-（2）LAB1.2 根据MUX21的testbench写DUT

提供了testbench文件tb_mux21_generic.vhd，用mux21元件，用behavioral和structural两种方式写parametric multiplexer。

tb_mux21_generic.vhd：

-- TestBench Template LIBRARY ieee;USE ieee.std_logic_1164.ALL;USE ieee.numeric_std.ALL;ENTITY TBMUX21_GENERIC ISEND TBMUX21_GENERIC;ARCHITECTURE TEST OF TBMUX21_GENERIC IS CONSTANT NBIT:INTEGER:=16;SIGNAL A1,B1,OUTPUT1,OUTPUT2:STD_LOGIC_VECTOR(NBIT-1 DOWNTO 0);SIGNAL S1:STD_LOGIC;-- Component DeclarationCOMPONENT MUX21_GENERICGENERIC(NBIT:INTEGER:=16);PORT(S : IN std_logic;A,B : IN std_logic_vector(NBIT-1 downto 0);       Y: OUT std_logic_vector(NBIT-1 downto 0));END COMPONENT;BEGIN-- Component Instantiationuut1: MUX21_GENERIC GENERIC MAP(NBIT)PORT MAP(A => A1,B => B1,S => S1,Y => OUTPUT1);uut2: MUX21_GENERIC GENERIC MAP(NBIT)PORT MAP(A => A1,B => B1,S => S1,Y => OUTPUT2);--  Test Bench Statementstb : PROCESSBEGINwait for 100 ns; -- wait until global set/reset completes-- Add user defined stimulus hereA1 <= "0000000100000001";B1 <= "1000000000000001";S1 <= '0', '1' AFTER 20 ns;wait; -- will wait foreverEND PROCESS tb;--  End Test Bench END TEST;

基本元件mux21： 

library IEEE;
use IEEE.STD_LOGIC_1164.ALL;entity mux21 isPORT(A,B,S:IN STD_LOGIC;Y	 :OUT STD_LOGIC);
end mux21;architecture DATAFLOW of mux21 is
beginY<=A WHEN S='0' ELSE B;
end DATAFLOW;

那么parametric multiplexer的

STRUCTURAL形式：

library IEEE;
use IEEE.STD_LOGIC_1164.ALL;entity MUX21_GENERIC is
GENERIC(NBIT:INTEGER:=4);
PORT(A,B:IN STD_LOGIC_VECTOR(NBIT-1 DOWNTO 0);S:IN STD_LOGIC;Y:OUT STD_LOGIC_VECTOR(NBIT-1 DOWNTO 0));
end MUX21_GENERIC;architecture structural of MUX21_GENERIC is
component mux21 isport(A,B,S:IN STD_LOGIC;Y	 :OUT STD_LOGIC);
end component;
beginu: for i in 0 to nbit-1 generatemux: mux21 port map (A => A(i),B => B(i),S => S,Y => Y(i));end generate;end structural;

BEHAVIORAL形式：

library IEEE;
use IEEE.STD_LOGIC_1164.ALL;entity MUX21_GENERIC_BEH is
GENERIC (NBIT:INTEGER:=4);
PORT(A,B:IN STD_LOGIC_VECTOR(NBIT-1 DOWNTO 0);S :IN STD_LOGIC;Y :OUT STD_LOGIC_VECTOR(NBIT-1 DOWNTO 0));
end MUX21_GENERIC_BEH;architecture Behavioral of MUX21_GENERIC_BEH isbeginPROCESS(A,B,S)BEGINIF(S='0') THEN Y<=A;ELSE Y<=B;END IF;END PROCESS;end Behavioral;

 可以看出，structural和behavioral两种描述形式在综合器中是不同的。

最后附上模拟结果：