From 533a0bd328e5eb4b798270ebe9260ad0f4b74e0b Mon Sep 17 00:00:00 2001
From: Jens Ahrensfeld <jens@jayfield.org>
Date: Fri, 24 Oct 2008 20:56:28 +0000
Subject: [PATCH] - Intital revision

git-svn-id: http://moon:8086/svn/vhdl/trunk@102 cc03376c-175c-47c8-b038-4cd826a8556b
---
 lib/FIFO/src/fifo_async.vhd | 113 ++++++++++++++++++++++++++++++++++++
 1 file changed, 113 insertions(+)
 create mode 100644 lib/FIFO/src/fifo_async.vhd

diff --git a/lib/FIFO/src/fifo_async.vhd b/lib/FIFO/src/fifo_async.vhd
new file mode 100644
index 0000000..cacf393
--- /dev/null
+++ b/lib/FIFO/src/fifo_async.vhd
@@ -0,0 +1,113 @@
+-------------------------------------------------------------------------
+-- Project: JCPU, a portable 8-bit RISC CPU written in VHDL
+-- This file: Dual-ported register file with asynchrous read
+
+-- Copyright (C) 2007 J. Ahrensfeld
+
+-- This library is free software; you can redistribute it and/or
+-- modify it under the terms of the GNU Lesser General Public
+-- License as published by the Free Software Foundation; either
+-- version 2.1 of the License, or (at your option) any later version.
+
+-- This library 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
+-- Lesser General Public License for more details.
+
+-- You should have received a copy of the GNU Lesser General Public
+-- License along with this library; if not, write to the Free Software
+-- Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301  USA
+
+-- For questions and ideas, please contact the author at jens@jayfield.org
+
+-----------------------------------------------------------------------
+
+LIBRARY IEEE;
+USE IEEE.STD_LOGIC_1164.ALL;
+USE IEEE.NUMERIC_STD.ALL;
+
+entity fifo_async is
+	Generic
+	(
+		addr_width			: natural := 4;
+		data_width			: natural := 8;
+		almost_full_thresh	: integer := 12;
+		almost_empty_thresh	: integer := 4
+	);
+	Port
+	(
+		rst			: in  STD_LOGIC;
+		clk_w		: in  STD_LOGIC;
+		clk_r		: in  STD_LOGIC;
+		we_w		: in  STD_LOGIC;
+		re_r		: in  STD_LOGIC;
+		fifo_full	: out STD_LOGIC;
+		fifo_empty	: out STD_LOGIC;
+		fifo_afull	: out STD_LOGIC;
+		fifo_aempty	: out STD_LOGIC;
+		data_w		: in  unsigned (data_width-1 downto 0);
+		data_r		: out unsigned (data_width-1 downto 0)
+	);
+end fifo_async;
+
+architecture Behavioral of fifo_async is
+	
+	signal buf_we_w		: STD_LOGIC;
+	signal ptr_w		: unsigned (addr_width-1 downto 0);
+	signal ptr_r		: unsigned (addr_width-1 downto 0);
+	signal full			: STD_LOGIC;
+	signal empty		: STD_LOGIC;
+	signal almost_full	: STD_LOGIC;
+	signal almost_empty	: STD_LOGIC;
+	
+begin
+
+	buf_we_w <= we_w;
+	fifo_full <= full;
+	fifo_empty <= empty;
+	fifo_afull <= almost_full;
+	fifo_aempty <= almost_empty;
+	
+inst_fifo_ctrl: entity work.async_fifo_ctrl
+	GENERIC MAP
+	(
+		addr_width			=> ADDR_WIDTH,
+		almost_full_thresh	=> almost_full_thresh,
+		almost_empty_thresh	=> almost_empty_thresh
+	)
+	PORT MAP
+	(
+		rst			=>	rst,
+		clk_w		=>	clk_w,
+		clk_r		=>	clk_r,
+		we			=>	we_w,
+		re			=>	re_r,
+		ptr_w		=>	ptr_w,
+		ptr_r		=>	ptr_r,
+		fifo_full	=>	full,
+		fifo_empty	=>	empty,
+		fifo_afull	=>	almost_full,
+		fifo_aempty	=>	almost_empty
+
+	);
+
+inst_dpram_1w1r: entity work.dpram_1w1r
+	GENERIC MAP
+	(
+		addr_width	=> addr_width,
+		data_width	=> data_width
+	)
+	PORT MAP(
+		clka		=> clk_w,
+		clkb		=> clk_r,
+		en_a		=> '1',
+		en_b		=> '1',
+		we_a		=> buf_we_w,
+		addr_a		=> ptr_w,
+		addr_b		=> ptr_r,
+		din_a		=> data_w,
+		dout_b		=> data_r
+	);
+
+end Behavioral;
+