Hello everybody,



I am trying to read keys (1 to 10) as input, store it in a ram (memory) and write it out in the reverse order with respect to the rounds ie. for 1st round, 10th key should be printed. I am doing this for reversing keys in aes_decryption crpytographic algorithm. I have tried in all the possible methods but could not succeed in running the code successfully. Could someone help me in that?



CODE:



library IEEE;
use IEEE.STD_LOGIC_1164.all;
use IEEE.Numeric_Std.all;

entity ram_dec is
port (
clock : in std_logic;
we : in std_logic;
address : in std_logic_vector(3 downto 0);
datain : in std_logic_vector(127 downto 0);
roundkey : out std_logic_vector(127 downto 0);
round : in std_logic_vector(3 downto 0)
);
end entity ram_dec;

architecture RTL of ram_dec is

type ram_type is array (0 to 9) of std_logic_vector(127 downto 0);
signal ram : ram_type;
signal read_address : std_logic_vector(3 downto 0);
-- signal rnd : bit_vector(3 downto 0);

begin

RamProc: process(clock) is

begin
if rising_edge(clock) then
if we = '1' then
-- for i in 1 to 10 loop
ram(to_integer(unsigned(read_address))) <= datain;
-- rnd <= std_logic_vector(unsigned(round) + 1);

-- read_address <= std_logic_vector(unsigned(read_address) + 1);
-- end loop;
end if;

-- elsif rising_edge(clock) then
elsif we = '0' then
-- read_address <= address;
-- for j in 10 downto 1 loop
case round is
when "0000" => read_address <= "1001";
when "0001" => read_address <= "1000";
when "0010" => read_address <= "0111";
when "0011" => read_address <= "0110";
when "0100" => read_address <= "0101";
when "0101" => read_address <= "0100";
when "0110" => read_address <= "0011";
when "0111" => read_address <= "0010";
when "1000" => read_address <= "0001";
when "1001" => read_address <= "0000";
when others => read_address <= "0000";
end case;

roundkey <= ram(to_integer(unsigned(read_address)));
-- end if;
-- end loop;
-- else
-- roundkey <= X"00000000000000000000000000000000";
end if;
end process RamProc;

end architecture RTL;



This is the code. I have tried writing a test bench for this but the roundkey output stays 'U' always. I searched for possible solutions in the net and tried converting std_logic_vector to bit_vector but unsigned was not supported for bit_vector and found that I will have to otherwise make sure that all std_logic values should not have values other than '0' or '1'. So, I tried assigning values to it in test bench but did not help. I will also copy my test bench. Could someone tell if my assignment is right or what else should I change in my code as I am somewhat new to VHDL programming.



-- TestBench Template

library IEEE;
use IEEE.STD_LOGIC_1164.all;
use IEEE.Numeric_Std.all;


ENTITY testbench IS
END testbench;

ARCHITECTURE behavior OF testbench IS

-- Component Declaration
component ram_dec is
port (
clock : in std_logic;
we : in std_logic;
address : in std_logic_vector(3 downto 0);
datain : in std_logic_vector(127 downto 0);
roundkey : out std_logic_vector(127 downto 0);
round : in std_logic_vector(3 downto 0)
);
end component;

signal clock : std_logic:= '0';
signal we : std_logic:= '0';
signal read_address : std_logic_vector(3 downto 0):= "0000";
signal datain : std_logic_vector(127 downto 0):= X"00000000000000000000000000000000";
signal roundkey: std_logic_vector(127 downto 0):= X"00000000000000000000000000000000";
signal round : std_logic_vector(3 downto 0):= "0000";

BEGIN

-- Component Instantiation
uut: ram_dec PORT MAP(
clock => clock,
we => we,
address => read_address,
datain => datain,
roundkey => roundkey,
round => round
);

ClockGen: process is
begin
-- while not StopClock loop
for i in 1 to 1000 loop
clock <= '0';
wait for 1 ns;
clock <= '1';
wait for 1 ns;
end loop;
wait;
end process ClockGen;


-- Test Bench Statements
tb : PROCESS
BEGIN
-- roundkey <= X"00000000000000000000000000000000";

wait for 10 ns; -- wait until global set/reset completes
we <= '1';
datain <= X"00010203050607080A0B0C0D0F101112";
round <= "0000";
wait for 4 ns;
datain <= X"14151617191A1B1C1E1F202123242526";
round <= "0001";
wait for 4 ns;
datain <= X"28292A2B2D2E2F30323334353738393A";
round <= "0010";
wait for 4 ns;
datain <= X"3C3D3E3F41424344464748494B4C4D4E";
round <= "0011";
wait for 4 ns;
datain <= X"50515253555657585A5B5C5D5F606162";
round <= "0100";
wait for 4 ns;
datain <= X"64656667696A6B6C6E6F707173747576";
round <= "0101";
wait for 4 ns;
datain <= X"78797A7B7D7E7F80828384858788898A";
round <= "0110";
wait for 4 ns;
datain <= X"8C8D8E8F91929394969798999B9C9D9E";
round <= "0111";
wait for 4 ns;
datain <= X"A0A1A2A3A5A6A7A8AAABACADAFB0B1B2";
round <= "1000";
wait for 4 ns;
datain <= X"B4B5B6B7B9BABBBCBEBFC0C1C3C4C5C6";
round <= "1001";
wait for 4 ns;



-- To print the data out

we <= '0';
round <= "0000";
wait for 4 ns;
round <= "0011";
wait for 4 ns;
round <= "1000";
wait for 4 ns;
round <= "1001";
wait;

END PROCESS tb;


END;



Thanks in advance,