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5i24/configs/hostmot2/source/timestamp.vhd

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+library IEEE;
+use IEEE.STD_LOGIC_1164.ALL;
+use IEEE.STD_LOGIC_ARITH.ALL;
+use IEEE.STD_LOGIC_UNSIGNED.ALL;
+
+--
+-- Copyright (C) 2007, Peter C. Wallace, Mesa Electronics
+-- http://www.mesanet.com
+--
+-- This program is is licensed under a disjunctive dual license giving you
+-- the choice of one of the two following sets of free software/open source
+-- licensing terms:
+--
+--    * GNU General Public License (GPL), version 2.0 or later
+--    * 3-clause BSD License
+-- 
+--
+-- The GNU GPL License:
+-- 
+--     This program is free software; you can redistribute it and/or modify
+--     it under the terms of the GNU General Public License as published by
+--     the Free Software Foundation; either version 2 of the License, 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 more details.
+-- 
+--     You should have received a copy of the GNU General Public License
+--     along with this program; if not, write to the Free Software
+--     Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301 USA
+-- 
+-- 
+-- The 3-clause BSD License:
+-- 
+--     Redistribution and use in source and binary forms, with or without
+--     modification, are permitted provided that the following conditions
+--     are met:
+-- 
+--         * Redistributions of source code must retain the above copyright
+--           notice, this list of conditions and the following disclaimer.
+-- 
+--         * Redistributions in binary form must reproduce the above
+--           copyright notice, this list of conditions and the following
+--           disclaimer in the documentation and/or other materials
+--           provided with the distribution.
+-- 
+--         * Neither the name of Mesa Electronics nor the names of its
+--           contributors may be used to endorse or promote products
+--           derived from this software without specific prior written
+--           permission.
+-- 
+-- 
+-- Disclaimer:
+-- 
+--     THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+--     "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+--     LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
+--     FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
+--     COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
+--     INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
+--     BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
+--     LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
+--     CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+--     LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
+--     ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+--     POSSIBILITY OF SUCH DAMAGE.
+-- 
+
+
+entity timestamp is
+    Port ( ibus : in std_logic_vector(15 downto 0);
+           obus : out std_logic_vector(15 downto 0);
+			  loadtsdiv : in std_logic;
+           readts : in std_logic;
+			  readtsdiv : in std_logic;
+			  tscount : out std_logic_vector (15 downto 0);
+           clk : in std_logic);
+end timestamp;
+
+architecture Behavioral of timestamp is
+
+signal counter: std_logic_vector (15 downto 0);
+signal div: std_logic_vector(15 downto 0);
+alias divmsb: std_logic is div(15);
+signal divlatch: std_logic_vector (15 downto 0);
+
+begin
+
+	atimestamp: process (clk,readts, counter, readtsdiv, divlatch)
+	begin
+		if rising_edge(clk) then
+			div <= div -1;
+			if divmsb = '1' then
+				div <= divlatch;
+		      counter <= counter + 1;
+			end if;
+			if loadtsdiv = '1' then
+				divlatch <= ibus;
+			end if;
+	 	end if; -- clk
+		obus <= (others => 'Z');
+		if readts = '1' then
+			obus <= counter;
+		end if;
+		if readtsdiv = '1' then
+			obus <= divlatch;
+		end if;	 
+	 tscount <= counter;
+	 end process;
+		
+end Behavioral;