vhdl - GHDL 挂起正在运行的测试平台

Question

在用 VHDL 测试一个简单的生命游戏实现时，在打印出“测试结束”消息后，空测试台的 GHDL 模拟以 100% 的 CPU 使用率挂起。

代码如下:

----- Package ------------------------------
library ieee;
use ieee.std_logic_1164.all;

package data_types is
    type array2D is array (0 to 10, 0 to 10) of std_logic;
end data_types;


----- Main Code ----------------------------
library ieee;
use ieee.std_logic_1164.all;
use work.data_types.all;

entity de0 is
    port (matrix : inout array2D);
end de0;


architecture life of de0 is

    -- Return the integer value of a cell, treating all out of bounds as 0
    function cellValue (matrix : array2D; x, y : integer) return integer is 
    begin
        if (y < 0 or y > matrix'high(1) or x < 0 or x > matrix'high(2) or matrix(y, x) = '0') then
            return 0;
        else
            return 1;
        end if;
    end cellValue;

begin

    -- Iterate over all cells
    row: for y in matrix'range(1) generate
        column: for x in matrix'range(2) generate

            process

                variable neighbours : integer := cellValue(matrix, x - 1, y - 1) +
                                                cellValue(matrix, x - 1, y) +
                                                cellValue(matrix, x - 1, y + 1) +
                                                cellValue(matrix, x, y - 1) +
                                                cellValue(matrix, x, y + 1) +
                                                cellValue(matrix, x + 1, y - 1) +
                                                cellValue(matrix, x + 1, y) +
                                                cellValue(matrix, x + 1, y + 1);

            begin

                -- Update the cell value according to the game of life rules
                if (neighbours = 2 or neighbours = 3) then
                    matrix(y, x) <= '1';
                else
                    matrix(y, x) <= '0';
                end if;

            end process;

        end generate;
    end generate;

end life;

还有测试台:

library ieee;
use ieee.std_logic_1164.all;
use work.data_types.all;

entity life_tb is
end life_tb;

architecture behaviour of life_tb is
    component life
        port (matrix : inout array2D);
    end component;

    for test: life use entity work.de0;
    signal matrix : array2D;

begin

    test: life port map (matrix => matrix);

    process
    begin
            assert false
                report "End of test" severity note;

            wait;

    end process;
end behaviour;

Answer 1

de0生命中的进程既没有敏感列表，也没有等待语句，所以这个进程会一直运行下去，只是在同一仿真时间无限循环执行进程中的语句，因此仿真不会停下来。

您可以通过添加敏感度列表 (matrix) 或在某些条件下等待来解决此问题。