如何在 VHDL 中的测试台中初始化数组？

Question

在下面的代码中，主要问题是数组没有被测试台初始化。

我的主要目的是设计下面的读地址输出指令的单元。主要输入 "INSTRUCTION_ADRESS" 是一个包含地址及其内容的数组。

我们将非常重视任何意见。

library IEEE;
use IEEE.std_logic_1164.all;

PACKAGE MIPS_PACKAGE is

    type INSTRUCTION_ARRAY is array (0 to 31) of std_logic_vector(31 downto 0);

end PACKAGE MIPS_PACKAGE;


    -- INSTRUCTION MEMORY --
    library IEEE;
    use IEEE.STD_LOGIC_1164.ALL;
    use ieee.numeric_std.all;
    use IEEE.std_logic_unsigned."+";

    use work.MIPS_PACKAGE.all;

    entity INSTRUCTION_MEMORY is
            port(

                PCSrc : in STD_LOGIC;
                PC_EXT : in STD_LOGIC_VECTOR (31 downto 0);

                INSTRUCTION_ADDRESS : in    INSTRUCTION_ARRAY;  
                INSTRUCTION     : out   STD_LOGIC_VECTOR (31 downto 0)

                );
    end INSTRUCTION_MEMORY;

    architecture INST_MEM of INSTRUCTION_MEMORY is

           Signal PC: std_logic_vector (31 downto 0):="00000000000000000000000000000100";
            Signal PC_ADD4: std_logic_vector (31 downto 0):=X"00000000";        

    begin

            INSTRUCTION <= INSTRUCTION_ADDRESS(to_integer(unsigned(PC))); -- INSTRUCTION MEMORY
            PC_ADD4 <= PC + X"4"; -- ADD 4

            MUX_PC: process(PCSrc)

                begin
                    if( PCSrc = '0') then
                        PC <= PC_ADD4; 
                    else
                        PC <= PC_EXT;
                    end if;
                end process MUX_PC; 


    end INST_MEM;

    ----------
    --TESTBENCH

    library IEEE;
    use IEEE.Std_logic_1164.all;
    use IEEE.Numeric_Std.all;

    use work.MIPS_PACKAGE.all;

    entity INSTRUCTION_MEMORY_tb is
    end;

    architecture bench of INSTRUCTION_MEMORY_tb is

      component INSTRUCTION_MEMORY
            port(
                PCSrc : in STD_LOGIC;
                PC_EXT : in STD_LOGIC_VECTOR (31 downto 0);
                INSTRUCTION_ADDRESS : in    INSTRUCTION_ARRAY;  
                    INSTRUCTION     : out   STD_LOGIC_VECTOR (31 downto 0)
                );
      end component;

      signal PCSrc: STD_LOGIC;
      signal PC_EXT: STD_LOGIC_VECTOR (31 downto 0);
      signal TestMemory: INSTRUCTION_ARRAY;
      signal INSTRUCTION: STD_LOGIC_VECTOR (31 downto 0) ;

    begin

      uut: INSTRUCTION_MEMORY port map ( PCSrc               => PCSrc,
                                         PC_EXT              => PC_EXT,
                                         INSTRUCTION_ADDRESS => TestMemory,
                                         INSTRUCTION         => INSTRUCTION );

      stimulus: process
      begin

        -- Put initialisation code here

    PCSrc  <= '0';
    PC_EXT <= "00000000000000000000000000000000";    
    TestMemory(0)   <= "10001100000000010000000000000000";  
    wait for 1 ns;

    PCSrc  <= '0';
    PC_EXT <= "00000000000000000000000000000000"; 
    TestMemory(4)   <= "10001100000000100000000000000001"; 
    wait for 1 ns;

    PCSrc  <= '0';
    PC_EXT <= "00000000000000000000000000000000";
    TestMemory(8)   <= "00000000001000101000000000100000";  

    PCSrc  <= '0';
    PC_EXT <= "00000000000000000000000000000000";
    TestMemory(12)  <= "00000010000000011000100000100000";  
    wait for 1 ns;

    PCSrc  <= '0';
    PC_EXT <= "00000000000000000000000000000000";
    TestMemory( 16 )  <= "10101100000100000000000000000011";  
    wait for 5 ns;

        -- Put test bench stimulus code here

        wait;
      end process;


    end;

Answer 1

所以我只是通过 Vivado 运行你的代码，在这个模拟器中，数组确实按照它应该的方式进行了初始化：

注意 TestMemory 波形每纳秒变化一次，正如预期的那样。由于您从未初始化整个数组，因此其他值当然保持 'U'。

现在，您可以看到指令仅在2ns 后发生变化，但这与未初始化数组无关。这是因为 MUX_PC: process(PCSrc) 在其敏感列表中只有 PCSrc，这意味着该过程只会执行一次 PCSrc 实际更改。这很可能不是预期的行为（这意味着您的 PC 只能在 PCSrc 更改时增加）。为了解决这个问题，在你的设计中加入一个时钟，设计一个同步过程。

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