Subversion Repositories xmatchpro

--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
 
-- e_mail : j.l.nunez-yanez@byacom.co.uk
 
-------------------------------------------------
--  ENTITY       = INPUT_COUNTER	           --
--  version      = 1.0                         --
--  last update  = 30/5/01                     --
--  author       = Jose Nunez                  --
-------------------------------------------------
 
 
-- FUNCTION
-- 8 bit counter for the read and write of the input buffer
 
 
--  PIN LIST
--  ENABLE = enable count 
--  CLEAR = asyncronus clear of the counter
--  CLEAR_COUNTERS : syncronous clear of counters
--  CLK   = master clock
--  COUNT = count output
 
 
library ieee,dzx;
use ieee.std_logic_1164.all;
use dzx.bit_arith.all;
use dzx.bit_utils.all; 
 
entity INPUT_COUNTER is
 
port (ENABLE : in bit;
	  CLEAR : in bit;
	  CLEAR_COUNTERS : in bit;
	  CLK : in bit;
	  COUNT : out bit_vector(7 downto 0)
     );
 
end INPUT_COUNTER;
 
architecture STRUCTURAL of INPUT_COUNTER is
 
signal COUNT_AUX : bit_vector(7 downto 0);
 
begin
 
COUNTING : process (CLK,CLEAR,ENABLE,CLEAR_COUNTERS)
 
begin
     	-- asynchronous RESET signal forces all outputs LOW
      if (CLEAR = '0') then
	    COUNT_AUX <= "00000000";
	    -- check for +ve clock edge
	  elsif ((CLK'event) and (CLK = '1')) then
	  	    if (CLEAR_COUNTERS = '1') then
			       COUNT_AUX <= "00000000";
	          elsif( ENABLE = '1') then
	  	           COUNT_AUX <= COUNT_AUX+"00000001";
			  else
			       COUNT_AUX <= COUNT_AUX;
			  end if;
	 end if;
 
end process COUNTING;
 
COUNT <= COUNT_AUX;
 
end STRUCTURAL;