Basic memory unit help

library ieee;

use ieee.std_logic_1164.all;

use ieee.numeric_std.all;

entity Mem is

generic (N: integer; -- N bits wide (# of columns)

         K: integer); -- K bits long (# of rows)

port (Din: IN std_logic_vector (N-1 downto 0);

      clk,rw_en: IN std_logic;

      add_in: IN std_logic_vector (K-1 downto 0);

      Dout: OUT std_logic_vector (N-1 downto 0));

end Mem;

architecture behavior of Mem is

type mem_array is array (2**K-1 downto 0) of std_logic_vector (N-1 downto 0);

signal our_array: mem_array := (others =>(others => '0'));

begin

process (clk, Din, rw_en, add_in)

--variable address: integer;

begin

  if (clk = '1' and clk'event) then

    if (rw_en = '1') then

      our_array (to_int(unsigned(add_in))) <= Din;

    else

      Dout <= our_array (to_int(unsigned(add_in)));

    end if;

  end if;

end process;

end behavior;