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-- Desc: Asynch ROM

-- Author: Odd Rune

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library ieee;

use ieee.std_logic_1164.all;

use ieee.std_logic_unsigned.all;

use work.leval_package.all;

use std.textio.all;

use ieee.numeric_std.all;

entity inst_mem is

    generic ( memsize, addrbits, databits  : integer;

              initfile : string);

        port (

                clk : in std_logic;

                addr : in std_logic_vector(addrbits - 1 downto 0);

                dout : out std_logic_vector(databits - 1 downto 0);

                din : in std_logic_vector(databits - 1 downto 0);

                we : in std_logic

        );

end entity inst_mem;

architecture behav of inst_mem is

type rom_type is array(0 to memsize) of bit_vector(databits - 1

downto 0);

impure function init_rom(filename : in string) return rom_type is

        file romfile : text is in filename;

        variable li : line;

        variable ROM : rom_type;

        begin

                for i in rom_type'range loop

                        readline(romfile, li);

                        read(li, ROM(i));

                end loop;

        return ROM;

end function;

signal ROM : rom_type := init_rom(initfile);

signal read_reg : std_logic_vector(addrbits - 1 downto 0);

begin

        process(clk,addr)

        begin

                if rising_edge(clk) then

                        if we = '1' then

                                ROM(to_integer(unsigned(addr))) <= to_bitvector(din);

                        end if;

                        read_reg <= addr;

                end if;

        end process;

        dout <= to_stdlogicvector(ROM(to_integer(unsigned(read_reg))));

end architecture behav;