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

-- Title      :

-- Project    : 

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

-- File       : latch synch

-- Author     : kulmala3

-- Created    : 01.07.2005

-- Last update: 05.01.2006

-- Description: OUT: regular fifo IN: output asynchronous ack/nack IF

--

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

-- Copyright (c) 2005 

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

-- Revisions  :

-- Date        Version  Author  Description

-- 01.07.2005  1.0      AK      Created

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

library ieee;

use ieee.std_logic_1164.all;

use ieee.std_logic_arith.all;

use ieee.std_logic_unsigned.all;

entity aif_read_out is

  generic (

    data_width_g : integer := 32

    );

  port (

    clk       : in  std_logic;

    rst_n     : in  std_logic;

    a_we_in   : in  std_logic;

    ack_out   : out std_logic;

    empty_out : out std_logic;

    re_in     : in  std_logic;

    data_in   : in  std_logic_vector(data_width_g-1 downto 0);

    data_out  : out std_logic_vector(data_width_g-1 downto 0)

    );

end aif_read_out;

architecture rtl of aif_read_out is

  constant stages_c : integer := 3;

  signal ack_r           : std_logic;

  signal received_data_r : std_logic;

  -- synchronizer, last two are xorred

  signal a_we_r          : std_logic_vector(stages_c-1 downto 0);

  signal data_r          : std_logic_vector(data_width_g-1 downto 0);

begin

  data_out <= data_r;

--  ack_out <= ack_r;

  process (clk, rst_n)

  begin  -- process

    if rst_n = '0' then                 -- asynchronous reset (active low)

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

      ack_r           <= '0';

      ack_out         <= '0';

      received_data_r <= '0';

      empty_out       <= '1';

    elsif clk'event and clk = '1' then  -- rising clock edge

      for i in 0 to stages_c-2 loop

        a_we_r(i+1) <= a_we_r(i);

      end loop;  -- i

      a_we_r(0) <= a_we_in;

      -- now wait until we can write it to fifo

      if (a_we_r(stages_c-1) xor a_we_r(stages_c-2)) = '1' then

        ack_r           <= not ack_r;

        received_data_r <= '1';

        data_r          <= data_in;

        empty_out       <= '0';

      else

        ack_r <= ack_r;

      end if;

      if re_in = '1' and received_data_r = '1' then

        -- acknowledge, stop writing

        ack_out         <= ack_r;

        empty_out       <= '1';

        received_data_r <= '0';

      end if;

    end if;

  end process;

end rtl;