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1、1请画出下段程序的真值表，并说明该电路的功能。 LIBRARY ieee; USE ieee.std_logic_1164.all; ENTITY aaa ISPORT( oe,dir :IN STD_LOGIC ;a,b : INOUT STD_LOGIC_VECTOR(7 DOWNTO 0 ) ;END aaa ; ARCHITECTURE ar OF aaa IS BEGINPROCESS(oe , dir ) 输入 输出BEGIN a1 a0 x3 x2 x1 x0IF oe=0 THEN ab THEN ahbb100aQQQQQQQain,b=bin,co=d,so=e);u2 :
2、 h_adder port map(a=e,b=cin,co=f,so=sum);u3 : or2a port map(d,f,cout); end fd1; （5）1. 试用 VHDL 语言编程实现一个总线开关，其真值表如下：输 入输 出 enselectA0A6B0B6Y0Y6 0x“ZZZZZZZ” 10A 11B1. 总线开关的参考程序如下： LIBRARY ieee; USE ieee.std_logic_1164.all; (1) ENTITY aaa ISPORT( en, select : IN STD_LOGIC ;A, B : IN STD_LOGIC_VECTOR(6 D
3、OWNTO 0 ) ;Y : OUT STD_LOGIC_VECTOR(6 DOWNTO 0)END aaa ; (4) ARCHITECTURE ar OF aaa IS BEGINPROCESS(en, select )BEGINIF en=0 THEN Y pstate pstate pstate pstate pstate pstate pstate dout dout dout dout dout dout dout0) ; -计数器异步复位 ELSIF CLKEVENT AND CLK=1 THEN -检测时钟上升沿IF EN = 1 THEN -检测是否允许计数（同步使能）IF
4、CQI 0); -大于9，计数值清零 END IF;END IF;END IF; IF CQI = 9 THEN COUT cout cout cout cout LED7S LED7S LED7S LED7S LED7S LED7S LED7S LED7S LED7S LED7S LED7S LED7S LED7S LED7S LED7S LED7S NULL ;END CASE ;END PROCESS ;END ; 关于数据选择器饿设计关于数据选择器饿设计1、4选选1多路选择器的多路选择器的IF语句描述语句描述library ieee;use ieee.std_logic_1164.al
5、l;entity multiplexers_1 isport (a, b, c, d : in std_logic;s : in std_logic_vector (1 downto 0);o : out std_logic);end multiplexers_1;architecture archi of multiplexers_1 isbeginprocess (a, b, c, d, s)beginif (s = “00“) then o o o o o code code code code code code code code code = B else 0;end archi;
6、2、4位比较器（顺序描述）位比较器（顺序描述）Library ieee;Use ieee.std_logic_1164.all;Entity comp is Port (a,b:in std_logic_vector ( 3 downto 0);C: out std_logic_vector ( 2 downto 0);End comp;Architecture ex3 of comp is Begin Process ( a,b )BeginIf ab then cb else“010“ when a=b else“001“;End archi;根据原理图编程根据原理图编程Library i
7、eee;Use ieee.std_logic_1164.all;Entity adder is Port ( ai,bi: in std_logic;ci,si: out std_logic);End adder;Architecture archi of adder is Signal e,f: std_logic;beginE0);elsif rising_edge(clk)thenif en=1thenif up=1thencount=count+1;else count=count-1;end if;end if;end if;end process;sum=count;end a;
