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

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

--

-- Revision Control Information

--

-- $RCSfile: altera_tse_timing_adapter_fifo8.v,v $

-- $Source: /ipbu/cvs/sio/projects/TriSpeedEthernet/src/RTL/MAC/mac/timing_adapter/altera_tse_timing_adapter_fifo8.v,v $

--

-- $Revision: #1 $

-- $Date: 2008/08/09 $

-- Check in by : $Author: sc-build $

-- Author      : SKNg

--

-- Project     : Triple Speed Ethernet - 10/100/1000 MAC

--

-- Description : SIMULATION ONLY

--

-- simple atlantic fifo FOR 8BIT IMPLEMENTATION

-- 

-- ALTERA Confidential and Proprietary

-- Copyright 2006 (c) Altera Corporation

-- All rights reserved

--

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

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

library ieee ;

use ieee.std_logic_1164.all ;

use ieee.std_logic_arith.all ;

use ieee.std_logic_unsigned.all ;

 ENTITY  loopback_adapter_fifo is

     generic (

       DEPTH      : integer := 2048;

       DATA_WIDTH : integer := 11;

       ADDR_WIDTH : integer := 11

     );

         PORT

         (

                 clk            :       IN  STD_LOGIC;

                 reset          :       IN  STD_LOGIC;

                 in_valid   :   in  std_logic;

                 in_data    :   in  std_logic_vector(10 downto 0);

                 out_ready      :       IN  STD_LOGIC;

                 in_ready       :       out  STD_LOGIC;

                 out_valid  :   out  std_logic;

                 out_data   :   out  std_logic_vector(10 downto 0);

                 fill_level :   out  std_logic_vector(11 downto 0)

         );

   end loopback_adapter_fifo;

  architecture behav of loopback_adapter_fifo is

   -- use array to define the bunch of internal temparary signals

   type ram_type is array (0 to DEPTH-1) of

        std_logic_vector(DATA_WIDTH-1 downto 0);

   signal mem: ram_type;

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

   --| Signals

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

   signal wr_addr                       : std_logic_vector (ADDR_WIDTH-1 downto 0);

   signal rd_addr                       : std_logic_vector (ADDR_WIDTH-1 downto 0);

   signal next_wr_addr          : std_logic_vector (ADDR_WIDTH-1 downto 0);

   signal next_rd_addr          : std_logic_vector (ADDR_WIDTH-1 downto 0);

   signal mem_rd_addr           : std_logic_vector (ADDR_WIDTH-1 downto 0);

   signal empty                 : std_logic;

   signal full                  : std_logic;

   signal out_ready_vector      : std_logic;

   signal j                             : integer;

   signal enable_reading        : std_logic;

   signal out_valid_r   : std_logic;

   signal in_ready_r   : std_logic;

   begin

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

   --| FIFO Status

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

   process (out_ready,wr_addr,rd_addr,full)

   begin

      out_ready_vector                                  <= out_ready;

      in_ready_r                                        <= not (full);

      next_wr_addr                                      <= wr_addr + 1;

      next_rd_addr                                      <= rd_addr + 1;

      fill_level(ADDR_WIDTH-1 downto 0) <= wr_addr - rd_addr;

      fill_level(ADDR_WIDTH)                    <= '0';

      if (full = '1') then

           fill_level <= conv_std_logic_vector(DEPTH, 12);

          end if;

   end process;

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

  --| Manage Pointers

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

  process (reset,clk)

   begin

     if (reset = '1') then

            enable_reading <= '0';

     elsif (rising_edge(clk)) then

                 if (empty = '1') then

                        enable_reading <= '0';

             else

                  if (in_data(1) = '1' and in_valid = '1') then

                   enable_reading <= '1';

                  end if;

             end if;

         end if;

   end process;

   process (reset,clk)

   begin

    if (reset = '1') then

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

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

          empty    <= '1';

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

          full     <= '0';

          out_valid_r <= '0';

     elsif (rising_edge(clk)) then

          out_valid_r <= enable_reading;

          if (in_ready_r = '1' and in_valid = '1') then

             wr_addr <= next_wr_addr;

             empty   <= '0';

          end if;

          if (next_wr_addr = rd_addr) then

             full <= '1';

          end if;

          if (out_ready_vector ='1' and  out_valid_r = '1') then

            rd_addr <= next_rd_addr;

            full    <= '0';

                if (next_rd_addr = wr_addr) then

                  empty     <= '1';

                  out_valid_r <= '0';

                 end if;

           end if;

         if (out_ready_vector = '1' and out_valid_r = '1' and in_ready_r = '1' and in_valid = '1') then

           full  <= full;

           empty <= empty;

          end if;

      end if;

   end process;

   process (rd_addr,out_ready,out_valid_r,next_rd_addr)

   begin

      mem_rd_addr <= rd_addr;

      if (out_ready = '1' and out_valid_r = '1') then

        mem_rd_addr <= next_rd_addr;

      end if;

   end process;

   --assign output 

   out_valid <= out_valid_r;

   in_ready <= in_ready_r;

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

   --| Infer Memory

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

   process (reset,clk)

   begin

      if (reset = '1') then

             for i in 0 to (DEPTH-1) loop

              mem(conv_integer(i)) <= (others => '0');

                 end loop;

      elsif (rising_edge(clk)) then

         if (in_ready_r = '1' and in_valid = '1')       then

           mem(conv_integer(wr_addr)) <= in_data;

                 end if;

         out_data <= mem(conv_integer(mem_rd_addr));

      end if;

   end process;

   end behav;