CODE
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LIBRARY ieee;
USE ieee.std_logic_1164.ALL;
use ieee.numeric_std.ALL;

entity DataMEMORY is
    Port ( MAR : in  STD_LOGIC_vector (15 downto 0);
           MDR : in  STD_LOGIC_vector (15 downto 0);
           WE : in std_logic;

           Readdata : out  STD_LOGIC_vector (15 downto 0));
end DataMEMORY;
architecture Behavioral of DataMEMORY is
type dataMemory  is array (0 to 65535) of std_logic_vector(15 downto 0);
signal DM : dataMemory:=((others=> (others=>'0')));
begin

process (MAR)
begin
if (WE='1') then
DM(to_integer(unsigned(MAR)))<=MDR;

end if ;


end process;

Readdata<=DM(to_integer(unsigned(MAR)));
end Behavioral;




TESTBENCH
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LIBRARY ieee;
USE ieee.std_logic_1164.ALL;
use ieee.numeric_std.ALL;
-- Uncomment the following library declaration if using
-- arithmetic functions with Signed or Unsigned values
--USE ieee.numeric_std.ALL;

ENTITY DataMEMORYTB IS
END DataMEMORYTB;

ARCHITECTURE behavior OF DataMEMORYTB IS

    -- Component Declaration for the Unit Under Test (UUT)

    COMPONENT DataMEMORY
    PORT(
         MAR : IN  std_logic_vector(15 downto 0);
         MDR : IN  std_logic_vector(15 downto 0);
         WE : IN  std_logic ;

         Readdata : OUT  std_logic_vector(15 downto 0)
        );
    END COMPONENT;


   --Inputs
   signal MAR : std_logic_vector(15 downto 0) := (others => '0');
   signal MDR : std_logic_vector(15 downto 0) := (others => '0');
   signal WE : std_logic := '0';

 	--Outputs
   signal Readdata : std_logic_vector(15 downto 0);
   -- No clocks detected in port list. Replace <clock> below with
   -- appropriate port name


BEGIN

	-- Instantiate the Unit Under Test (UUT)
   uut: DataMEMORY PORT MAP (
          MAR => MAR,
          MDR => MDR,
          WE => WE,
          Readdata => Readdata
        );




   -- Stimulus process
   stim_proc: process
   begin


      -- insert stimulus here
WE<='1';
MAR<="1000000000000000";
MDR<="1010101010101010";
wait for 100 ns;
WE<='0';
MAR<="1000000000000000";
wait for 100 ns;
MAR<="1100000000000000";
WE<='1';
MDR<="1000000000000000";
wait for 100 ns;

MAR<="0000000000000000";
WE<='0';
wait for 100 ns;

MAR<="0000000000000010";
WE<='0';
wait for 100 ns;

      wait;
   end process;

END;