source: PROJECT_CORE_MPI/MPI_HCL/BRANCHES/v1.0/IP_Timer.vhd

---------------------------------------------------------------------------------
-- Company: 
-- Engineer: 
-- 
-- Create Date:    15:11:13 01/16/2014 
-- Design Name: 
-- Module Name:    IP_Timer - Behavioral 
-- Project Name: 
-- Target Devices: 
-- Tool versions: 
-- Description: 
--
-- Dependencies: 
--
-- Revision: 
-- Revision 0.01 - File Created
-- Additional Comments: 
--
----------------------------------------------------------------------------------

library ieee;
use ieee.std_logic_1164.all;
use ieee.std_logic_unsigned.all;
-- Uncomment the following library declaration if using
-- arithmetic functions with Signed or Unsigned values
use IEEE.NUMERIC_STD.ALL;

-- Uncomment the following library declaration if instantiating
-- any Xilinx primitives in this code.
--library UNISIM;
--use UNISIM.VComponents.all;

entity IP_Timer is

port (clk,reset,upDn,load,start:in std_logic;
loadval :in std_logic_vector(31 downto 0);
outval : out std_logic_vector(31 downto 0);
zero : out std_logic);

end IP_Timer;

architecture Behavioral of IP_Timer is
signal count: std_logic_vector(31 downto 0);
signal z:std_logic:='1';
begin
process (clk) 
begin
   if clk='1' and clk'event then
      if reset='1' then 
         count <= (others => '0');
                        z<='1';
      elsif start='1' then
         if load='1' then
            count <= loadval;
         else 
            if UpDn='1' then   
               count <= count + 1;
            else
               count <= count - 1;
            end if;
         end if;
                        if count=0 then
                                z<='1';
                        else
                                z<='0';
                        end if;
      end if;
   end if;
end process; 
OutVal<=count;
zero<=z;
end Behavioral;