如果一个码是即时码或唯一可译码，则它满足Kraft-McMillan不等式。对吗

是的，这是正确的。根据Kraft-McMillan不等式，对于任何一组长度为$l_1, l_2, ..., l_n$的码字，如果它们是即时码或唯一可译码，则它们所在的编码树的叶节点数不超过$2^{\sum_{i=1}^n (-l_i)}$，这个值也被称为“Kraft-McMillan参数”。同时，任何满足这个不等式的码字集合都可以构成一个即时码或唯一可译码。

相关问题

用vhdl语言编写一个将二进制码转换成 0-E 的七段码译码器

好的，我可以为您编写一个简单的七段码译码器的VHDL代码，将二进制码转换为0-E的七段码。以下是代码：

entity binary_to_7seg is
    Port ( bin : in STD_LOGIC_VECTOR (3 downto 0);
           seg : out STD_LOGIC_VECTOR (6 downto 0));
end binary_to_7seg;

architecture Behavioral of binary_to_7seg is
begin
    process(bin)
    begin
        case bin is
            when "0000" => seg <= "1000000"; -- 0
            when "0001" => seg <= "1111001"; -- 1
            when "0010" => seg <= "0100100"; -- 2
            when "0011" => seg <= "0110000"; -- 3
            when "0100" => seg <= "0011001"; -- 4
            when "0101" => seg <= "0010010"; -- 5
            when "0110" => seg <= "0000010"; -- 6
            when "0111" => seg <= "1111000"; -- 7
            when "1000" => seg <= "0000000"; -- 8
            when "1001" => seg <= "0011000"; -- 9
            when "1010" => seg <= "0001000"; -- A
            when "1011" => seg <= "0000011"; -- b
            when "1100" => seg <= "1000110"; -- C
            when "1101" => seg <= "0100001"; -- d
            when "1110" => seg <= "0000110"; -- E
            when "1111" => seg <= "0001110"; -- F
            when others => seg <= "-------"; -- invalid input
        end case;
    end process;
end Behavioral;

这个代码的输入是一个4位的二进制码，输出是一个7位的七段码。当输入的二进制码不是0-F之间的值时，输出将为"-------"，表示无效输入。

VHDL18个拨码开关3-8译码器控制数码管的数字显示

以下是VHDL代码：

library ieee;
use ieee.std_logic_1164.all;
use ieee.numeric_std.all;

entity decoder is
    port (
        switches : in std_logic_vector(17 downto 0); -- 18个拨码开关
        segments : out std_logic_vector(6 downto 0); -- 数码管7段显示输出
        cathodes : out std_logic_vector(3 downto 0) -- 数码管位选控制输出
    );
end entity decoder;

architecture behavioral of decoder is
    signal binary : std_logic_vector(2 downto 0); -- 3位二进制数，用于控制译码器
begin

    -- 3-8译码器的真值表
    process(switches)
    begin
        case switches(17 downto 16) is
            when "00" => binary <= "000"; -- switch 17-16 = 00，译码器输出 Y0
            when "01" => binary <= "001"; -- switch 17-16 = 01，译码器输出 Y1
            when "10" => binary <= "010"; -- switch 17-16 = 10，译码器输出 Y2
            when "11" => binary <= "011"; -- switch 17-16 = 11，译码器输出 Y3
        end case;
    end process;

    -- 数码管7段显示的真值表
    process(binary, switches)
    begin
        case binary is
            when "000" => -- 译码器输出 Y0
                segments <= "00111111"; -- 数字 0
                cathodes <= "1110"; -- 第1位数码管
            when "001" => -- 译码器输出 Y1
                segments <= "00000110"; -- 数字 1
                cathodes <= "1101"; -- 第2位数码管
            when "010" => -- 译码器输出 Y2
                segments <= "01011011"; -- 数字 2
                cathodes <= "1011"; -- 第3位数码管
            when "011" => -- 译码器输出 Y3
                segments <= "01001111"; -- 数字 3
                cathodes <= "0111"; -- 第4位数码管
        end case;
    end process;

end architecture behavioral;

以上代码实现了18个拨码开关控制3-8译码器，进而控制数码管的数字显示。其中，3-8译码器的输出 Y0-Y3 分别对应数字 0-3 的7段显示编码。同时，使用了一个二进制信号 binary 来控制译码器的输出。数码管的位选控制则使用了另外一个信号 cathodes，通过对其赋不同的值来控制不同的数码管显示。