Read and Write File

In VHDL, you can read and write files using the textio package. The textio package provides procedures and functions for reading and writing text files. You can use the textio package to read data from a file into a variable or write data from a variable to a file.

Reading from a File

We can use the TextIO library to handle file operations in VHDL. This feature is useful for reading input from files during simulation. Here's how to read inputs from a file:

library ieee;
use ieee.std_logic_1164.all;
use std.textio.all;

entity read_file is
end read_file;

architecture rtl of read_file is
    file input_file : text open read_mode is "input.txt";
    variable line : line;
    variable data : integer;
begin
    while not endfile(input_file) loop
        readline(input_file, line);
        read(line, data);
        report "Read data: " & integer'image(data);
    end loop;
    file_close(input_file);
    wait;
end rtl;

Code above shows an example of reading data from a file in VHDL. The file input.txt is opened in read mode, and data is read line by line using the readline procedure. The data is then converted to an integer using the read function and displayed using the report statement.

Writing to a File

We can also write testbench results to a file for further analysis. Use the TextIO library's write and writeline functions to save data to a file:

library ieee;
use ieee.std_logic_1164.all;
use std.textio.all;

entity write_file is
end write_file;

architecture rtl of write_file is
    file output_file : text open write_mode is "output.txt";
    variable data : integer := 42;
begin
    write(output_file, data);
    writeline(output_file, "Data written to file: " & integer'image(data));
    file_close(output_file);
    wait;
end rtl;

For more information on the textio package, refer to the IEEE Standard VHDL Language Reference Manual.