VHDL textio hread problem

Hi Tricky,

Thanks for your response. With a bit of playing I managed to get your code working and I have used it in my simulation. I had to declare the function as impure and I put in a check for the end of file for a bit of safety. This is what i ended up with:

LIBRARY ieee;
USE ieee.std_logic_1164.all;
USE ieee.numeric_std.all;
LIBRARY STD;
USE STD.textio.all;
LIBRARY work;
ENTITY test_program_file_io IS
	GENERIC
	(
		filename	: string := "prog_file.txt";
		data_width	: integer := 8;
		addr_width	: integer := 15
	);
	PORT
	(
		address		: IN std_logic_vector(addr_width-1 DOWNTO 0);
		rd		: IN std_logic;
		
		rddata		: OUT std_logic_vector(data_width-1 DOWNTO 0)
	);
END ENTITY;
ARCHITECTURE sim OF test_program_file_io IS
	CONSTANT N : integer := (2**addr_width);
	
	TYPE rom_t IS ARRAY (0 TO N-1) OF std_logic_vector(7 DOWNTO 0);
	
	IMPURE FUNCTION init_rom RETURN rom_t IS
		FILE rom_file   : text OPEN read_mode IS filename;
		VARIABLE ret    : rom_t;
		VARIABLE l      : line;
	BEGIN
		FOR i IN 0 TO N-1 LOOP
			IF(NOT ENDFILE(rom_file)) THEN
				readline(rom_file, l);
				hread(l, ret(i));
			END IF;
		END LOOP;
		
		RETURN ret;
	END FUNCTION init_rom;
	
	CONSTANT ROM    : rom_t := init_rom;
BEGIN
	PROCESS(rd, address)
	BEGIN
		IF(rd='1')THEN
			rddata <= ROM(to_integer(unsigned(address)));
		END IF;
	END PROCESS;
END ARCHITECTURE;

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technically correct, but you included the non-standard library std_logic_textio which is a 3rd party library that gave you the ability to read/write directly to std_logic/std_logic_vector with VHDL 1993. The functionality of this package is included in std_logic_1164 in VHDL 2008.

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Yes you are right, I was working with vhdl-1993 but updated my simulation to use vhdl-2008 so I could use the hread and cut a corner. I missed removing that library.

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Is there any reason you're making an asynchronous rom? and not a synchronous one?

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Not really, the application might not be the best. I was trying to improve my simulation skills and using it like a ROM I could connect it in my work simulation. My aim was to be able to read in a selected line from a input text file so I can dump a hex program to a text file and load it into my simulation sequentially. I also wanted to be able to start from somewhere other than the start of the file.

After playing I think that you are right and initializing an array is the simplest path.

Thanks

James