FPGA spartan 3 - X mod 3 内部没有时钟的组合过程

Question

我正在开展一个项目，其中一部分围绕着寻找 X mod 3 和 FPGA spartan 3 (Xilinx)， 在组合过程中。 事实上，在这个项目中，在这个 ALU 模块之前还有一些其他的模块是顺序的。 但在 ALU 模块内部，不允许使用顺序处理。 所以我尝试使用here中的一种方法：

这是一种简单的手动操作方法。由于 1 = 22 mod 3，我们得到 1 = 每个正整数 22n mod 3。此外 2 = 22n+1 mod 3。 因此，可以通过计数来确定一个整数是否可以被 3 整除 奇数位位置的 1 位，将此数字乘以 2，添加 偶数位位置的 1 位的数量将它们添加到结果中，并且 检查结果是否能被 3 整除。

示例：57₁₀=111001₂。奇数位有 2 位，有 2 位 在偶数位置。 2*2 + 2 = 6 可以被 3 整除。因此 57 是 能被 3 整除。

我已经在下面发布了我的代码。问题是在我连接两个不同信号中的奇数位和偶数位之后：

        mod_un_t1 <= A(6) & A(4)& A(2) & A(0);
        mod_un_t2 <= A(7) & A(5)& A(3) & A(1);

我丢失了所有数据，之后没有 if 语句起作用。我用测试台模拟了我的代码。但它总是给出：

result <= "00000000";

我已经对其进行了测试，我发现在连接之后不会传递任何数据。 我不能使用顺序网络和向上计数和向下计数方法，或者它们都与 clk 和顺序过程一起使用的移位寄存器方法。

任何人都可以帮助我，解决我的代码中的问题，如果有人有更好的方法或更好的实现方式，让我无处可去！！！

这是我的代码：

library ieee;
use ieee.std_logic_1164.all;
use ieee.numeric_std.all;
Use Ieee.std_logic_unsigned.all;

entity ALU is
   port ( A          : in  std_logic_vector (7 downto 0);   -- Input A
          B          : in  std_logic_vector (7 downto 0);   -- Input B
          FN         : in  std_logic_vector (3 downto 0);   -- ALU functions provided by the ALU_Controller (see the lab manual)
          result       : out std_logic_vector (7 downto 0);   -- ALU output (unsigned binary)
           overflow   : out std_logic;                       -- '1' if overflow ocurres, '0' otherwise 
           sign       : out std_logic                        -- '1' if the result is a negative value, '0' otherwise
        );
end ALU;

architecture behavioral of ALU is

signal mod_un_t1: std_logic_vector (3 downto 0);
signal mod_un_t2: std_logic_vector (3 downto 0);
signal mod_un_t3: std_logic_vector (3 downto 0);
signal mod_un_t4: std_logic_vector (3 downto 0);
signal mod_unsigned: std_logic_vector (3 downto 0);

signal mod_si_t1: std_logic_vector (3 downto 0);
signal mod_si_t2: std_logic_vector (3 downto 0);
signal mod_si_t3: std_logic_vector (3 downto 0);
signal mod_si_t4: std_logic_vector (3 downto 0);
signal mod_signed: std_logic_vector (3 downto 0);

begin
   process ( FN, A, B , result_tmp)
   begin
        result <= (others => '0');
        mod_un_t1 <= (others => '0');
        mod_un_t2 <= (others => '0');
        mod_un_t3 <= (others => '0');
        mod_un_t4 <= (others => '0');
        mod_unsigned <= (others => '0');
        mod_si_t1 <= (others => '0');
        mod_si_t2 <= (others => '0');
        mod_si_t3 <= (others => '0');
        mod_si_t4 <= (others => '0');
        mod_signed <= (others => '0');

        if (FN = "0100") then -- Unsigned (A) mod 3
            mod_un_t1 <= A(6) & A(4)& A(2) & A(0);
            mod_un_t2 <= A(7) & A(5)& A(3) & A(1);

            if(mod_un_t1= "1111") then
              mod_un_t3 <= "1000";
            elsif(mod_un_t1 = "1110" or mod_un_t1 = "1101" or  mod_un_t1 = "1011" or mod_un_t1 = "0111") then
                mod_un_t3 <= "0110";
            elsif(mod_un_t1 = "1100" or mod_un_t1 = "1010" or mod_un_t1 = "1001" or mod_un_t1 = "0110" or mod_un_t1 = "0101" or mod_un_t1 = "0011") then
                mod_un_t3 <= "0100";
            elsif(mod_un_t1 = "0001" or mod_un_t1 = "0010" or mod_un_t1 = "0100" or mod_un_t1 = "1000") then
                mod_un_t3 <= "0010";
            elsif (mod_un_t1 = "0000") then
                mod_un_t3 <= "0000";
            end if;

            if (mod_un_t2 = "1111") then
                mod_un_t4 <= "0100";
            elsif (mod_un_t2 = "1110" or mod_un_t2 = "1101" or mod_un_t2 = "1011" or mod_un_t2 = "0111") then
                mod_un_t4 <= "0011";
            elsif(mod_un_t2 = "1100" or mod_un_t2 = "1010" or mod_un_t2 = "1001" or mod_un_t2 = "0110" or mod_un_t2 = "0101" or mod_un_t2 = "0011") then
                mod_un_t4 <= "0010";
            elsif(mod_un_t2 = "0001" or mod_un_t2 = "0010" or mod_un_t2 = "0100" or mod_un_t2 = "1000") then
                mod_un_t4 <= "0001";
            elsif(mod_un_t2 = "0000") then
                mod_un_t4 <= "0000";
            end if;

            mod_unsigned <= mod_un_t3 + mod_un_t4;

            if  (mod_unsigned = "0010" or  mod_unsigned = "0101" or mod_unsigned ="0111" or mod_unsigned = "1010") then
                result <= "00000001";
            elsif (mod_unsigned = "0001" or mod_unsigned = "0100" or mod_unsigned = "1000" or mod_unsigned = "1011") then
                result <= "00000010";
            elsif (mod_unsigned = "0000" or mod_unsigned = "0011" or mod_unsigned = "0110" or mod_unsigned = "1001") then
                result <= "00000000";
            end if;
        end if;

   end process;
end behavioral;

Answer 1

进程敏感度列表中缺少似乎没有分配的信号。否则它们可能是变量，允许在当前仿真周期中使用它们而不会产生增量周期，因为信号分配直到结束或当前仿真周期才会生效。

变量的候选者似乎是：

signal mod_un_t1: std_logic_vector (3 downto 0);
signal mod_un_t2: std_logic_vector (3 downto 0);
signal mod_un_t3: std_logic_vector (3 downto 0);
signal mod_un_t4: std_logic_vector (3 downto 0);
signal mod_unsigned: std_logic_vector (3 downto 0);

signal mod_si_t1: std_logic_vector (3 downto 0);
signal mod_si_t2: std_logic_vector (3 downto 0);
signal mod_si_t3: std_logic_vector (3 downto 0);
signal mod_si_t4: std_logic_vector (3 downto 0);
signal mod_signed: std_logic_vector (3 downto 0);

这些声明可以更改为对象类变量并移至进程（begin 之前）。它们的信号分配 (<=) 将切换为变量分配 (:=)。

您可以简单地将出现在作业右侧的那些显示在敏感度列表中，但这会导致额外的增量周期。

如果有理由保留它们的信号，您可以考虑将您的进程分解为多个进程和/或其他并发语句。

敏感列表中有一个result_tmp，在您显示的代码中没有声明或赋值。

...能否请您提供一个简短的示例，将进程分解为多个进程和/或其他并发语句？

Aarchitecture foo of ALU is

    signal mod_un_t1: std_logic_vector (3 downto 0);
    signal mod_un_t2: std_logic_vector (3 downto 0);
    signal mod_un_t3: std_logic_vector (3 downto 0);
    signal mod_un_t4: std_logic_vector (3 downto 0);
    signal mod_unsigned: std_logic_vector (3 downto 0);

    signal mod_si_t1: std_logic_vector (3 downto 0);
    signal mod_si_t2: std_logic_vector (3 downto 0);
    signal mod_si_t3: std_logic_vector (3 downto 0);
    signal mod_si_t4: std_logic_vector (3 downto 0);
    signal mod_signed: std_logic_vector (3 downto 0);
    -- dummy 
    signal result_tmp: std_logic_vector(7 downto 0);

begin

    -- Concurrent signal assignments - these are just wires
    mod_un_t1 <= A(6) & A(4)& A(2) & A(0);
    mod_un_t2 <= A(7) & A(5)& A(3) & A(1); 

UNPROC1:
    process (FN, mod_un_t1)
    begin
    if FN = "0100" then
        case mod_un_t1 is
            when "0000" =>
                mod_un_t3 <= "0000";
            when "0001" | "0010" | "0100" | "1000" =>
                mod_un_t3 <= "0010";
            when "1100" | "1010" | "1001" | "0110" =>
                mod_un_t3 <= "0100";
            when "1110" | "1101" | "1011" | "0111" =>
                mod_un_t3 <= "0100";
            when others =>
            end case;
    else
    --
    end if;
end process;

UNPROC2:
    process (FN, mod_un_t2)
    begin
    if FN = "0100" then 
        if mod_un_t2 = "1111" then
            mod_un_t4 <= "0100";
        elsif mod_un_t2 = "1110" or mod_un_t2 = "1101" or mod_un_t2 = "1011" or mod_un_t2 = "0111" then
            mod_un_t4 <= "0011";
        elsif mod_un_t2 = "1100" or mod_un_t2 = "1010" or mod_un_t2 = "1001" or mod_un_t2 = "0110" or mod_un_t2 = "0101" or mod_un_t2 = "0011" then
            mod_un_t4 <= "0010";
        elsif mod_un_t2 = "0001" or mod_un_t2 = "0010" or mod_un_t2 = "0100" or mod_un_t2 = "1000" then
            mod_un_t4 <= "0001";
        elsif mod_un_t2 = "0000" then
            mod_un_t4 <= "0000";
        end if;
    else
        --
    end if;
end process;

ALU_PROC:  -- keep all the arithemetic operations in one process
    process (FN, mod_un_t3, mod_un_t4)
    begin
        if FN = "0100" then 
             mod_unsigned <= mod_un_t3 + mod_un_t4;
        else 

        end if;
    end process;

OUT_PROC: -- keep all the result assignment in one process
process (FN, mod_unsigned)
    begin
        if FN = "0100" then 
            if  mod_unsigned = "0010" or  mod_unsigned = "0101" or mod_unsigned ="0111" or mod_unsigned = "1010" then
                result <= "00000001";
            elsif mod_unsigned = "0001" or mod_unsigned = "0100" or mod_unsigned = "1000" or mod_unsigned = "1011" then
                result <= "00000010";
            elsif mod_unsigned = "0000" or mod_unsigned = "0011" or mod_unsigned = "0110" or mod_unsigned = "1001" then
                result <= "00000000";
            else 
            --
            end if;
        end if;
    end process;

end architecture foo;