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-- $Id: fifo_1c_dram.vhd 421 2011-11-07 21:23:50Z mueller $
--
-- Copyright 2007- by Walter F.J. Mueller <W.F.J.Mueller@gsi.de>
--
-- This program is free software; you may redistribute and/or modify it under
-- the terms of the GNU General Public License as published by the Free
-- Software Foundation, either version 2, or at your option any later version.
--
-- This program is distributed in the hope that it will be useful, but
-- WITHOUT ANY WARRANTY, without even the implied warranty of MERCHANTABILITY
-- or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
-- for complete details.
--
------------------------------------------------------------------------------
-- Module Name:    fifo_1c_dram - syn
-- Description:    FIFO, single clock domain, distributed RAM based, with
--                 enable/busy/valid/hold interface.
--
-- Dependencies:   fifo_1c_dram_raw
--
-- Test bench:     tb/tb_fifo_1c_dram
-- Target Devices: generic Spartan, Virtex
-- Tool versions:  xst 8.1, 8.2, 9.1, 9.2; ghdl 0.18-0.25
-- Revision History: 
-- Date         Rev Version  Comment
-- 2007-06-06    49   1.0    Initial version 
--
-- Some synthesis results:
-- - 2007-12-27 ise 8.2.03 for xc3s1000-ft256-4:
--   AWIDTH DWIDTH  LUT.l LUT.m  Flop   clock(xst est.)
--        4     16     31    32    22   153MHz     ( 16 words)
--        5     16     49    64    23   120MHz     ( 32 words)
--        6     16     70   128    23   120MHz     ( 64 words)
--        7     16    111   256    30   120MHz     (128 words)
------------------------------------------------------------------------------
 
library ieee;
use ieee.std_logic_1164.all;
 
use work.slvtypes.all;
use work.memlib.all;
 
entity fifo_1c_dram is                  -- fifo, 1 clock, dram based
  generic (
    AWIDTH : positive :=  7;            -- address width (sets size)
    DWIDTH : positive := 16);           -- data width
  port (
    CLK : in slbit;                     -- clock
    RESET : in slbit;                   -- reset
    DI : in slv(DWIDTH-1 downto 0);     -- input data
    ENA : in slbit;                     -- write enable
    BUSY : out slbit;                   -- write port hold    
    DO : out slv(DWIDTH-1 downto 0);    -- output data
    VAL : out slbit;                    -- read valid
    HOLD : in slbit;                    -- read hold
    SIZE : out slv(AWIDTH downto 0)     -- number of used slots
  );
end fifo_1c_dram;
 
 
architecture syn of fifo_1c_dram is
 
  signal WE : slbit := '0';
  signal RE : slbit := '0';
  signal SIZE_L : slv(AWIDTH-1 downto 0) := (others=>'0');
  signal EMPTY : slbit := '0';
  signal FULL : slbit := '0';
 
begin
 
  FIFO : fifo_1c_dram_raw
    generic map (
      AWIDTH => AWIDTH,
      DWIDTH => DWIDTH)
    port map (
      CLK   => CLK,
      RESET => RESET,
      WE => WE,
      RE => RE,
      DI => DI,
      DO => DO,
      SIZE => SIZE_L,
      EMPTY => EMPTY,
      FULL => FULL
    );
 
  WE <= ENA and (not FULL);
  RE <= (not EMPTY) and (not HOLD);
 
  BUSY <= FULL;
  VAL  <= not EMPTY;
  SIZE <= FULL & SIZE_L;
 
end syn;