Text I/O in VHDL

This post is not meant for first years

--code for reading from a text file
-- text write code by Binoy B. Nair, Lecturer EIE
-- this code reads a value from the file binoy_file.txt at each rising edge of clk
-- the execution ends when end of file is reached
-- first it must be made sure that the file(here binoy_file.txt)exists,before you try to read from it

library ieee;
use ieee.std_logic_1164.all;
use ieee.std_logic_unsigned.all;
use std.textio.all; -- this package must be included for all text read/write

entity reading is
port(clk:in std_logic);
end reading;

architecture reading_arch of reading is

signal sig_value: integer:=0; -- we will finally move this extracted value to this signal for easy observation

begin

process(clk)

file binoy_input_file : text is in "c:/binoy_file.txt"; -- open a file named binoy_file.txt
-- for reading from it (hence defined as in)
variable value: integer:=0; -- the read value is moved to this variable
variable in_line: line; -- the read value will be of type LINE always

begin

if clk'event and clk='1' then -- the process runs at every rising edge of clk

if (not(endfile(binoy_input_file))) then -- this code checks if the end of file has reached

readline( binoy_input_file,in_line);-- otherwise one line is read from the file.
-- Every time a line has been read, the file pointer automatically
-- points to the next line

read(in_line,value); -- converts the read variable 'in_line' from type LINE to data type of second operand(here INTEGER)

sig_value<=value; -- moving the contents of variable 'value' to a signal 'sig_value'
end if;
end if;
end process;
end reading_arch;




-- text write code by Binoy B. Nair, Lecturer EIE
-- this code counts the number of rising edges of clk input and writes to the file bin_out_text.txt

library ieee;
use ieee.std_logic_1164.all;
use ieee.std_logic_unsigned.all;
use std.textio.all; -- this package must be included for all text read/write

entity writing is
port(clk:in std_logic);
end writing;

architecture writing_arch of writing is
begin

process(clk)

file binoy_output_file : text is out "c:/bin_out_text.txt"; -- open a file named bin_out_text.txt
-- for writing to it (hence defined as OUT )
-- if no path is specified, the file bin_out_text.txt
-- will be stored in the same directory as the program

variable out_line: line; -- each value that is passed to out_line will be
-- considered to be a line and is auto. terminated by a carriage return

variable cnt: integer:=0;

begin

if clk'event and clk='1' then -- at every clk event, the count is incremented by 1
cnt:=cnt+1;

write (out_line,cnt); -- the value of count after incrementing is written to out_line
-- (this converts input data type (here INTEGER) to type LINE which can then be written to a file)
-- it is not possible to directly write the data type INTEGER to a file,
--hence the above conversion is needed.

writeline(binoy_output_file,out_line); -- write the out_line to the output file
end if;
end process;
end writing_arch;