Reading a Text File

What you see is the ASCII code of your text file.

LIBRARY ieee;
USE ieee.std_logic_1164.ALL;
USE ieee.std_logic_textio.ALL;
USE ieee.numeric_std.ALL;
USE std.textio.ALL;
ENTITY feeder IS
    PORT (
        start       : IN  std_logic;
        pixel_value : OUT std_logic_vector(7 DOWNTO 0)
        );
END feeder;
ARCHITECTURE Behavior OF feeder IS
    CONSTANT filename : string := "/afs/cad/u/s/m/smb34/vlsi2/frame1.txt";
    TYPE frame_array IS ARRAY (natural RANGE <>) OF std_logic_vector(7 DOWNTO 0);
    SIGNAL read_frame_array : frame_array(0 TO 25343);
BEGIN
    
    read_file : PROCESS (start) IS
        FILE file_in     : text;          -- file ID
        VARIABLE line_rd : line;          -- text line
        VARIABLE data_in : integer;       -- integer data input
        VARIABLE i       : integer := 0;  -- line counter
    BEGIN
        IF rising_edge(start) THEN
            file_open(file_in, filename, read_mode);
            WHILE (NOT endfile(file_in)) LOOP
                readline(file_in, line_rd);
                read(line_rd, data_in);
                read_frame_array(i) <= std_logic_vector(to_unsigned(data_in, 8));
                pixel_value <= read_frame_array(i);
                i := i + 1;
            END LOOP;
            file_close(file_in);
        END IF;
    END PROCESS read_file;
END Behavior;

thanks a lot for replying to my issue, but it does give me the following error for type of conversation

the error in this line command:

I see, you have to use the ieee.numeric_std.ALL instead of ieee.numeric_bit.ALL library.

dear schmalisch,

This undefined 'U' states occur when signals do not have a defined state right from the beginning of the simulation.

    read_file : PROCESS IS
        FILE file_in     : text;          -- file ID
        VARIABLE line_rd : line;          -- text line
        VARIABLE data_in : integer;       -- integer data input
        VARIABLE i       : integer := 0;  -- line counter
    BEGIN
        file_open(file_in, filename, read_mode);
        pixel_value <= (OTHERS => '0');
        WAIT UNTIL rising_edge(start);
        WHILE (NOT endfile(file_in)) LOOP
            readline(file_in, line_rd);
            read(line_rd, data_in);
            read_frame_array(i) <= std_logic_vector(to_unsigned(data_in, 8));
            pixel_value         <= std_logic_vector(to_unsigned(data_in, 8));
            i := i + 1;
            WAIT UNTIL rising_edge(start);
        END LOOP;
        file_close(file_in);
        WAIT;
    END PROCESS read_file;

thanks so much , not only for solving my problem but also for explaining to me why it went wrong.