用于纠正错误的 VHDL 汉明码答案

【问题标题】：VHDL Hamming code for correcting error用于纠正错误的 VHDL 汉明码
【发布时间】：2015-01-03 20:05:48
【问题描述】：

请帮助我使用 VHDL 中的汉明码检查此代码以纠正错误。我能够检测到错误但无法纠正它。我的编码器、解码器和错误注入器有三个模块。我感觉我的解码器有问题。下面是我的解码器代码

library ieee;
use ieee.std_logic_1164.all;

entity hamdec8 is
    port(
        datain: in std_logic_vector (7 downto 0);
        parin : in std_logic_vector(4 downto 0);
        Dataout : out std_logic_vector(7 downto 0);
        Parout : out std_logic_vector(4 downto 0);
        NE  : out std_logic;
        DED : out std_logic;
        SEC : out std_logic
        );
        Constant MaskP1 : std_logic_vector(7 downto 0) := "01011011";
        Constant MaskP2 : std_logic_vector(7 downto 0) := "01101101";
        Constant MaskP3 : std_logic_vector(7 downto 0) := "10001110";
        Constant MaskP4 : std_logic_vector(7 downto 0) := "11110000";
end hamdec8;

architecture beh of hamdec8 is
    signal synd : std_logic_vector(4 downto 1);
    signal P0 : std_logic;
    signal din1, din2, din3, din4 : std_logic_vector(7 downto 0); --to hold datain AND maskp
begin
    process(Datain, Parin)
    begin
        NE <= '1';
        DED <= '0';
        SEC <= '0';
        Dataout <= Datain;
        Parout <= Parin;
        P0 <=  (Parin(0) XOR Parin(1) XOR Parin(2) XOR Parin(3) XOR
            Parin(4) XOR Datain(0) XOR Datain(1) XOR Datain(2) XOR
            Datain(3) XOR Datain(4) XOR Datain(5) XOR Datain(6) XOR
            Datain(7));

        din1 <= Datain AND MaskP1;
        Synd(1) <= din1(0) XOR din1(1) XOR din1(2) XOR din1(3) XOR
            din1(4) XOR din1(5) XOR din1(6) XOR din1(7) XOR Parin(1);

        din2 <= Datain AND MaskP2;
        Synd(2) <= din2(0) XOR din2(1) XOR din2(2) XOR din2(3) XOR
            din2(4) XOR din2(5) XOR din2(6) XOR din2(7) XOR Parin(2);

        din3 <= Datain AND MaskP3;
        Synd(3) <= din3(0) XOR din3(1) XOR din3(2) XOR din3(3) XOR
            din3(4) XOR din3(5) XOR din3(6) XOR din3(7) XOR Parin(3);

        din4 <= Datain AND MaskP4;
        Synd(4) <= din4(0) XOR din4(1) XOR din4(2) XOR din4(3) XOR
            din4(4) XOR din4(5) XOR din4(6) XOR din4(7) XOR Parin(4);

        if (synd = "0000") then
            IF (P0 = '0') then
                --Dataout <= Datain;
                --NE <= '1';
                --DED <= '0';
                --SEC <= '0';
                --Parout <= Parin;
                null;
            elsif (P0 = '1') then --single error
                NE <= '0';
                DED <= '0';
                SEC <= '1';
                case synd is
                    when "0000" => Parout(0) <= NOT Parin(0);
                    when "0001" => Parout(1) <= NOT Parin(1);
                    when "0010" => Parout(2) <= NOT Parin(2);
                    when "0011" => Dataout(0) <= NOT Datain(0);
                    when "0100" => Parout(3) <= NOT parin(3);
                    when "0101" => Dataout(1) <= NOT Datain(1);
                    when "0110" => Dataout(2) <= NOT Datain(2);
                    when "0111" => Dataout(3) <= NOT Datain(3);
                    when "1000" => parout(4) <= parin(4);
                    when "1001" => Dataout(4) <= NOT Datain(4);
                    when "1010" => Dataout(5) <= NOT Datain(5);
                    when "1011" => Dataout(6) <= NOT Datain(6);
                    when "1100" => Dataout(7) <= NOT Datain(7);
                    when others =>
                        Parout <= parin;
                        Dataout <= Datain;
                end case;
                Dataout <= "00000000";
                Parout <= "00000";
            end if;
        elsif (P0 = '0') then
            if (synd /= "0000") then
                NE <= '0';
                DED <= '1';
                SEC <= '0';
                Dataout <= "00000000";
                Parout <= "00000";
            end if;
        end if;
    end process;
end beh;

谢谢

【问题讨论】：

标签： vhdl hamming-code

【解决方案1】：

case 语句中实现的校正逻辑只有在校验子为"0000" 且整体奇偶校验为'1' 时才会达到。这并没有涵盖所有其他可能的综合症值。单个错误elsif 的缩进使这令人困惑。您需要重新处理嵌套的 if 语句，以便对所有综合症应用更正。

【讨论】：

【解决方案2】：

您的信号P0、synd、din1、din2、din3、din4 应声明为进程中的变量，或者您应从进程中提取异或计算。

提取异或计算、扩展敏感度列表和固定代码缩进的第二个变体：

library ieee;
use     ieee.std_logic_1164.all;

entity hamdec8 is
  port (
    datain: in std_logic_vector (7 downto 0);
    parin : in std_logic_vector(4 downto 0);
    Dataout : out std_logic_vector(7 downto 0);
    Parout : out std_logic_vector(4 downto 0);
    NE  : out std_logic;
    DED : out std_logic;
    SEC : out std_logic
  );
end hamdec8;

architecture beh of hamdec8 is
  Constant MaskP1 : std_logic_vector(7 downto 0) := "01011011";
  Constant MaskP2 : std_logic_vector(7 downto 0) := "01101101";
  Constant MaskP3 : std_logic_vector(7 downto 0) := "10001110";
  Constant MaskP4 : std_logic_vector(7 downto 0) := "11110000";

  signal synd : std_logic_vector(4 downto 1);
  signal P0 : std_logic;
  signal din1, din2, din3, din4 : std_logic_vector(7 downto 0); --to hold datain AND maskp
begin

  P0 <= Parin(0) XOR Parin(1) XOR Parin(2) XOR Parin(3) XOR Parin(4) XOR
        Datain(0) XOR Datain(1) XOR Datain(2) XOR Datain(3) XOR Datain(4) XOR
        Datain(5) XOR Datain(6) XOR Datain(7);

  din1 <= Datain AND MaskP1;
  din2 <= Datain AND MaskP2;
  din3 <= Datain AND MaskP3;
  din4 <= Datain AND MaskP4;

  Synd(1) <= din1(0) XOR din1(1) XOR din1(2) XOR din1(3) XOR
             din1(4) XOR din1(5) XOR din1(6) XOR din1(7) XOR Parin(1);

  Synd(2) <= din2(0) XOR din2(1) XOR din2(2) XOR din2(3) XOR
             din2(4) XOR din2(5) XOR din2(6) XOR din2(7) XOR Parin(2);

  Synd(3) <= din3(0) XOR din3(1) XOR din3(2) XOR din3(3) XOR
             din3(4) XOR din3(5) XOR din3(6) XOR din3(7) XOR Parin(3);

  Synd(4) <= din4(0) XOR din4(1) XOR din4(2) XOR din4(3) XOR
             din4(4) XOR din4(5) XOR din4(6) XOR din4(7) XOR Parin(4);

  process(Datain, Parin, synd, P0)
  begin
    NE <= '1';
    DED <= '0';
    SEC <= '0';
    Dataout <= Datain;
    Parout <= Parin;

    if (synd = "0000") then
      IF (P0 = '0') then
        --Dataout <= Datain;
        --NE <= '1';
        --DED <= '0';
        --SEC <= '0';
        --Parout <= Parin;
        null;
      elsif (P0 = '1') then --single error
        NE <= '0';
        DED <= '0';
        SEC <= '1';
        case synd is
          when "0000" => Parout(0) <= NOT Parin(0);
          when "0001" => Parout(1) <= NOT Parin(1);
          when "0010" => Parout(2) <= NOT Parin(2);
          when "0011" => Dataout(0) <= NOT Datain(0);
          when "0100" => Parout(3) <= NOT parin(3);
          when "0101" => Dataout(1) <= NOT Datain(1);
          when "0110" => Dataout(2) <= NOT Datain(2);
          when "0111" => Dataout(3) <= NOT Datain(3);
          when "1000" => parout(4) <= parin(4);
          when "1001" => Dataout(4) <= NOT Datain(4);
          when "1010" => Dataout(5) <= NOT Datain(5);
          when "1011" => Dataout(6) <= NOT Datain(6);
          when "1100" => Dataout(7) <= NOT Datain(7);
          when others => null;
        end case;
        --Dataout <= "00000000";   -- these lines override all calculations
        --Parout <= "00000";       -- from previous case statement
      end if;
    elsif (P0 = '0') then
      if (synd /= "0000") then
        NE <= '0';
        DED <= '1';
        SEC <= '0';
        Dataout <= "00000000";
        Parout <= "00000";
      end if;
    end if;
  end process;
end beh;

【讨论】：

【解决方案3】：

这段代码是怎么回事？

IF (P0 = '0') then
    -- commented out stuff
    [...]
    null;
elsif (P0 = '1') then --single error
    [...]
end if;

为什么不直接使用：

if p0 = '1' then
    [...]
end if;

至少

if p0 = '0' then
    [stuff for when p0 is '0']
else
    [stuff for when p0 is not '0']
end if;

【讨论】：