arrays - VHDL 数组 - 我如何声明一个未知大小的数组并使用它

Question

我的要求是从输入文件中读取数据位并将数据写入 vhdl 中的内存阵列(输出)。由于我不知道输入文件中的数据量，因此我需要声明未知大小的数组并在稍后阶段将数据分配给内存。

我的代码如下:

声明:

PACKAGE io IS
   type memory is array (natural range<>) of std_logic_vector(3 downto 0); 
END;

entity File_io is
 port (
     clk:             in  std_logic;
     Data_memory:     out   memory
 );
end entity;

architecture behav of File_io is
 signal mem: memory;
begin
 process(clk)
   begin
     for i in 0 to 15 loop  -- Took just 16 values for explaination purpose.
                             -- i may need more values to be written which is unknown.
      mem(i) <= std_logic_vector(to_unsigned(i, 4));
     end loop;
    Data_memory <= mem;
  end process;
end architecture behav;

我已将实际代码最小化到我的确切要求。如果有任何语法错误，请忽略。

问题是我无法为不受约束的数组赋值，即未定义大小。我该怎么做呢 ？有什么建议或替代方案吗？指导我

Answer 1

查看您的其他问题 - How to Eliminate whitespaces while Reading a file in VHDL提供了一个示例内存初始化文件以及读取它的问题。

合并该修复程序并使用方法方法 J.H. Bonarius 建议产生一个 Minimal, Complete and Verifiable example :

library ieee;
use ieee.std_logic_1164.all;

PACKAGE io IS
   type memory is array (natural range<>) of std_logic_vector(3 downto 0); 
   function iswhitespace (inpstr: in string) return boolean;
END;

package body io is
    function iswhitespace (inpstr:  in  string) return boolean is
        constant NBSP: character  := character'val(128); 
    begin
        for i in inpstr'range loop
            if inpstr(i) /= ' ' and inpstr(i) /= NBSP and inpstr(i) /= HT then
                exit;
            elsif i = inpstr'RIGHT then
                return TRUE;
            end if;
        end loop;
        return FALSE;
    end function;
end package body;

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

entity File_io is
    generic (
        constant MEMORY_SIZE: natural := 42;
        constant filename:  string := "C:\Users\ChowdaryS\Downloads\topo.bin"
    );
     port (
         clk:             in  std_logic;
         Data_memory:     out   memory (0 to MEMORY_SIZE - 1) 
     );
end entity;

architecture foo of File_io is
    signal mem: memory (0 to MEMORY_SIZE - 1); -- ADDED subtype indication
    use ieee.numeric_std.all;                  -- MISSING cntext item
    use std.textio.all;
    signal mem_inited:     boolean := FALSE;   -- ADDED
begin
    process(clk)
        file f:       text open read_mode is filename;
        variable L:   line;
        variable i:   integer:= 0;
        variable b:   bit_vector(3 downto 0);  
    begin
        if not mem_inited then
            i := 0;
            while not endfile(f) loop
                readline(f, L);
                while L.all'length >= b'length and not iswhitespace(L.all) loop
                    read(L, b);
                    mem(i) <= to_stdlogicvector(b);
                    i := i + 1;
                end loop;
            end loop;
            report "mem values loaded = " &  integer'image(i);
            mem_inited <= TRUE;
        end if;
    end process;
    Data_memory <= mem;
end architecture foo;

有变化。函数 iswhitespace 已添加到包 io 中。您可以查看上面引用的权衡问题以及是否需要。

输出端口的分配已移出流程。假定您将在该过程中对 mem 进行某种写入。

还有一个测试台实例化 file_io 并确定内存数组的大小，将其作为通用传递。

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

entity file_io_tb is
end entity;

architecture foo of file_io_tb is

    constant MEMSIZ:    natural := 16;
    constant filename:  string := "topo.bin";  -- found locally.
    signal clk:         std_logic := '0';
    signal Data_memory: memory (0 to MEMSIZ - 1);
    use std.textio.all;

    impure function getarraysize return natural is
        variable L:     Line;
        variable i:     natural;
        variable b:     bit_vector (3 downto 0);
        file f:         text  open read_mode is filename;
    begin
        i := 0;
        while not endfile(f) loop
            readline(f, L);
            while L.all'length >= b'length and not iswhitespace(L.all) loop
                read(L, b);
                i := i + 1;
            end loop;
        end loop;
        report " memory size = " & integer'image(i);
        return i;
    end function;
begin
DUT:
    entity work.file_io
        generic map (MEMORY_SIZE => getarraysize, filename => filename)
        port map (
            clk => clk,
            Data_memory => Data_memory
        );

CLOCK:
    process
    begin
        wait for 10 ns;
        clk <= not clk;
        if now > 50 ns then
            wait;
        end if;
    end process;

end architecture;

该功能是在细化时执行文件读取以设置泛型。

我们看到这个初始化内存:

使用的 topo.bin 副本在第一行有四个尾随空格:

10101100 11010100 10101100 11010100   

11111110 10111001 11111110 10111001

波形中显示的值与 topo.bin 中的上述两行匹配。

(所有这些都是为了在另一个问题中找到空白问题而写的)。