. USE IEEE. .ALL;
USE IEEE.STD_LOGIC_UNSIGNED.ALL; ENTITY CNT10 IS PORT ( CLK : IN STD_LOGIC ; Q : OUT STD_LOGIC_VECTOR(3 DOWNTO 0)) ; END CNT10;
ARCHITECTURE bhv OF IS SIGNAL Q1 : STD_LOGIC_VECTOR(3 DOWNTO 0); BEGIN PROCESS (CLK) IF THEN -- 边沿检测 IF Q1 > 10 THEN Q1 <= (OTHERS => '0'); -- 置零 ELSE Q1 <= Q1 + 1 ; -- 加1 END IF; END IF; END PROCESS ; ; -- 输出 END bhv;
2．以下程序是BCD码表示0～99计数器的VHDL描述，试补充完整。 LIBRARY IEEE;
USE IEEE.STD_LOGIC_1164.ALL; USE ; ENTITY cnt100b is port( clk, rst, en : in std_logic; cq : out std_logic_vector(7 downto 0); -- 计数输出 cout: out std_logic); -- 进位输出 END ENTITY cnt100b;
bhv of cnt100b is BEGIN PROCESS (clk, rst, en) cqi : std_logic_vector(7 downto 0); BEGIN if rst = '1' then cqi := ; -- 计数器清零 else if then -- 上升沿判断 if en = '1' then if cqi(3 downto 0) < \ -- 比较低4位 ; -- 计数加1
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.
else if cqi(7 downto 4) < \-- 比较高4位 cqi := cqi + 16; else cqi := (others => '0'); end if;
-- 低4位清零
cqi ( ) := “0000”;
end if; end if; ; end if; if cqi = “ ” then cout <= '1'; else cout <= '0'; end if; ; END PROCESS;
-- 判断进位输出
END ARCHITECTURE bhv;
3．以下程序是多路选择器的VHDL描述，试补充完整。 LIBRARY IEEE;
USE IEEE.STD_LOGIC_1164.ALL; ENTITY bmux IS
PORT ( sel : STD_LOGIC;
A, B : IN STD_LOGIC_VECTOR(7 DOWNTO 0); Y
: STD_LOGIC_VECTOR(7 DOWNTO 0)) ;
END bmux;
ARCHITECTURE bhv OF bmux IS BEGIN
y <= A when sel = '1' ; END ;
4．以下程序是10/4线优先编码器的VHDL描述，试补充完整。 LIBRARY IEEE ;
USE IEEE. .ALL;
ENTITY coder IS
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. PORT ( din : IN STD_LOGIC_VECTOR( ); output : STD_LOGIC_VECTOR(3 DOWNTO 0) ); END coder;
ARCHITECTURE behav OF IS
SIGNAL SIN : STD_LOGIC_VECTOR(3 DOWNTO 0); BEGIN
PROCESS ( ) BEGIN
IF (din(9)='0') THEN SIN <= \ ELSIF ( ) THEN SIN <= \ ELSIF (din(7)='0') THEN SIN <= \ ELSIF (din(6)='0') THEN SIN <= \ ELSIF (din(5)='0') THEN SIN <= \ ELSIF (din(4)='0') THEN SIN <= \ ELSIF (din(3)='0') THEN SIN <= \ ELSIF (din(2)='0') THEN SIN <= \ ELSIF (din(1)='0') THEN SIN <= \ ELSE ; ； END PROCESS ； ； END behav; 五、程序分析题
1．以下程序是四选一数据选择器的VHDL描述，请分析程序并画出原理图或详述其功能
LIBRARY IEEE;
USE IEEE.STD_LOGIC_1164.ALL; ENTITY multi_4v IS
PORT(S : IN STD_LOGIC_VECTOR (1 DOWNTO 0); A,B,C,D : IN STD_LOGIC; Y : OUT STD_LOGIC); END multi_4v;
ARCHITECTURE a OF multi_4v IS BEGIN
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. PROCESS BEGIN
IF (S=\ Y <= A;
ELSIF (S=\ Y <= B;
ELSIF (S=\ Y <= C;
ELSIF (S=\ Y <= D; END IF; END PROCESS; END a;
2．下面是同步清零可逆计数器的程序，请分析程序并画出原理图或详述其功能 LIBRARY IEEE;
USE IEEE.STD_LOGIC_1164.ALL; USE IEEE.STD_LOGIC_UNSIGNED.ALL; ENTITY countud IS
PORT(clk :IN STD_LOGIC; clr :IN STD_LOGIC; dire :IN STD_LOGIC;
q :BUFFER STD_LOGIC_VECTOR(7 DOWNTO 0)); END countud;
ARCHITECTURE a OF countud IS BEGIN
PROCESS(clk) BEGIN
IF clk'event AND clk='1' THEN IF clr='0' THEN
q<=\ ELSIF dire='1' THEN
q<=q+1;
ELSE q<=q-1; END IF;
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. END IF; END PROCESS; END a；
3．以下程序是上升沿计数器的VHDL描述，请分析程序并画出原理图或详述其功能
LIBRARY IEEE;
USE IEEE.STD_LOGIC_1164.ALL; ENTITY three IS
PORT(clk,d : IN
STD_LOGIC;
Dout : OUT STD_LOGIC );
END;
ARCHITECTURE bhv OF three IS
SIGNAL tmp: STD_LOGIC; BEGIN
P1: PROCESS(clk) BEGIN
IF rising_edge(clk) THEN
Tmp <= d; dout <= tmp;
END IF;
END PROCESS P1; END bhv; 六、程序阅读理解题
1．以下程序能实现加和减功能的计数器，请在划线空白处注释该句的功能 Library ieee; Use ieee.std_logic_1164.all; Use ieee.std_logic_unsigned.all;
Entity up_down is Port(clk,rst,en,up: in std_logic;
Sum: Cout:
out std_logic);
out std_logic_vector(2 downto 0);
End up_down;
Architecture a of up_down is Signal count: std_logic_vector(2 downto 0); Begin
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