Hi guys,requesting some help with my vhdl code,i am writing a Data 
Encryption Standard using VHDL.I have a problem with reading from a 
file.I can write to a file if I entered the inputs manually in my 
testbench but I cant write to a file when I try to read the inputs from 
a file.Below is a portion of my code and the input/output files.Any help 
would be greatly appreciated and thanks for your time!

Input File(.txt)
_________________
785AC3A4BD0FE12D
123456789ABCDEF0
785AC3A4BD0FE12D


Output File(.txt)
_________________
1335 ns FD9CBA5D26331F38
2135 ns 17EA4A8B48C14DA0
2935 ns FD9CBA5D26331F38




Code(data_in<=input,data_out<=output)
____________________________________________
-- data_in <= x"785AC3A4BD0FE12D",
-- x"123456789ABCDEF0" after 1400 ns,
-- x"785AC3A4BD0FE12D" after 2200 ns;

1

process 

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use std.textio.all;

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use ieee.numeric_std.all;

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file inputfile:text open read_mode is "input.txt";

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variable ipa:std_logic_vector(63 downto 0);

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variable inline:line;

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begin

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 while not(endfile(inputfile))loop

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  readline(inputfile,inline);

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  read(inline,ipa);

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  data_in<=ipa;

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  wait for 4000 ns;

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 end loop;

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 wait;

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end process;

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 function_select <= '1';

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 --'0' after 2100 ns,

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 --'1' after 4550 ns,

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 --'0' after 5800 ns;

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 tb: PROCESS

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 BEGIN

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  key <= x"38A84FF898B90B8F";

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  wait for 1400 ns;

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 end process;

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 process

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  use std.textio.all;

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  use ieee.numeric_std.all;

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  file resultfile:text open write_mode is "result.txt";

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  variable outline:line;

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 begin

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  wait on data_out;

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  wait for 50 ns;

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  write(outline,now,right, 2);

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  hwrite(outline,data_out,right, 40);

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  writeline(resultfile,outline);

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 end process;

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end key;

Darren Seow wrote:
> but I cant write to a file when I try to read the inputs from a file.
Why not? What error message do you get?

Hi there,sorry for the late reply,issue has been solved.I forgotten to 
add a "h"in front of read.Hence,it wasnt able to read hexadecimal 
inputs.Thanks for your time!