代码如下，实现的是数码管显示的代码：
library ieee;
use ieee.std_logic_1164.all;
use ieee.std_logic_unsigned.all;
Entity smg is
port
(
Clock: in std_logic;
Input_value: in integer range 0 to 9; --input data
En: out std_logic_vector(7 downto 0);
Display: out std_logic_vector(7 downto 0)
);
end smg;
Architecture Decoder of smg is
--Signal Counter: Integer range 0 to 7;
Begin
process(clock)
Variable Num:Integer range 0 to 9;
Variable Counter: Integer range 0 to 7;
Begin
if falling_edge(Clock) then
if Counter = 7 then
Counter :=0;
else
counter :=Counter + 1;
end if;
case Counter is --Duan xuan
when 0 =>
En <= "11111110";
Num := Input_value;
when 1 =>
En <= "11111101";
Num := Input_value;
when 2 =>
En <= "11111011";
Num := Input_value;
when 3 =>
En <= "11110111";
Num := Input_value;
when 4 =>
En <= "11101111";
Num := Input_value;
when 5 =>
En <= "11011111";
Num := Input_value;
when 6 =>
En <= "10111111";
Num := Input_value;
when 7 =>
En <= "01111111";
Num := Input_value;
end case;
case Num is --Wei Xuan
when 0=>
Display <= X"FC";
when 1=>
Display <= X"60";
when 2=>
Display <= X"DA";
when 3=>
Display <= X"F2";
when 4=>
Display <= X"66";
when 5=>
Display <= X"B6";
when 6=>
Display <= X"BE";
when 7=>
Display <= X"E0";
when 8=>
Display <= X"FE";
when 9=>
Display <= X"F6";
when others=> --貌似这里没起作用
Display <= X"00";
End case;
End if;
End Process;
最后一个others好像没起作用，四个位表示BCD码输入 输入0到9显示是正常的。但是只要超过9就乱了，
按道理有了最后一个others约束应该输出的是全灭。但偏偏不是，所以很疑惑。
麻烦路过的过目下，谢谢！！
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