vhdl stopwatch with LPM RAM

Hi,

I am doing a lab assignment about a VHDL stopwatch.

this watch can store 16 32-bits timestamp in the memory.

and when readmode = '1', the stopwatch will show the timestamps.

below is my code.(the other modules are working fine, only this one doesn't work yet.) could anybody tell me what is wrong with it?

I really appreciate it.

--- Quote Start ---

LIBRARY ieee;

USE ieee.std_logic_1164.all;

use ieee.std_logic_unsigned.all;

use ieee.numeric_std.all;

entity stopwatch is

port

(

clk : in std_logic;

readmode : in std_logic;

reset : in std_logic;

store : in std_logic;

data_ram : in std_logic_vector(31 downto 0);

data_clock : in std_logic_vector(31 downto 0);

addr_user : in std_logic_vector(3 downto 0);

ram_write_en: out std_logic;

addr : out std_logic_vector(3 downto 0);

data : out std_logic_vector(31 downto 0)

);

end stopwatch;

ARCHITECTURE arch_stopwatch of stopwatch is

TYPE state_type IS (s0,s1,s2,s3,s4,s5,s6,s7,s8,s9,s10,s11,s12,s13,s14,s15,s16);

signal state : state_type := s0;

signal stage : std_logic_vector(3 downto 0);

signal flag : std_logic_vector(1 downto 0);

signal c_store, n_store : std_logic;

signal fall_edge : std_logic;

begin

flag <= reset & readmode;

n_store <= store;

fall_edge <= c_store and ( not n_store );

process(clk, reset)

begin

if( reset = '1' ) then

c_store <= '1';

elsif( rising_edge(clk) ) then

c_store <= n_store;

end if;

end process;

process

variable r_counter : std_logic_vector(3 downto 0);

begin

WAIT UNTIL (clk'event and clk = '1');

if( flag = "10" or flag = "11" ) then

stage <= "0000";

state <= s0;

ram_write_en <= '1';

--addr <= (others => '0');

data <= (others => '0');

------------------------reset Memory------------------------

for i in 0 to 15 loop

addr <= r_counter;

r_counter := r_counter + 1;

end loop;

------------------------------------------------

elsif( flag = "00" ) then

data <= data_clock;

-------------store time---------

CASE state IS

WHEN s0 =>

ram_write_en <= '0';

stage <= "0000";

state <= s1;

when s1 =>

if(fall_edge = '1') then

addr <= stage;

ram_write_en <= '1';

stage <= stage + 1;

else

ram_write_en <= '0';

end if;

if( stage = "1111" ) then

state <= s2;

else

state <= s1;

end if;

when s2 =>

when others =>

state <= s0;

END CASE;

---------------------------------

elsif( flag = "01" ) then

ram_write_en <= '0';

addr <= addr_user;

data <= data_ram;

end if;

end process;

end arch_stopwatch;

--- Quote End ---