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------------------------------------------------------------------------------- -- -- The timer unit. -- -- $Id: t400_timer.vhd,v 1.1 2006-05-20 02:47:12 arniml Exp $ -- -- Copyright (c) 2006 Arnim Laeuger (arniml@opencores.org) -- -- All rights reserved -- -- Redistribution and use in source and synthezised 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 synthesized 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 the author nor the names of other contributors may -- be used to endorse or promote products derived from this software without -- specific prior written permission. -- -- 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 AUTHOR 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. -- -- Please report bugs to the author, but before you do so, please -- make sure that this is not a derivative work and that -- you have the latest version of this file. -- -- The latest version of this file can be found at: -- http://www.opencores.org/cvsweb.shtml/t400/ -- ------------------------------------------------------------------------------- library ieee; use ieee.std_logic_1164.all; use work.t400_pack.all; entity t400_timer is port ( -- System Interface ------------------------------------------------------- ck_i : in std_logic; ck_en_i : in boolean; por_i : in boolean; icyc_en_i : in boolean; -- Skip Interface --------------------------------------------------------- op_i : in skip_op_t; c_o : out boolean ); end t400_timer; library ieee; use ieee.numeric_std.all; architecture rtl of t400_timer is signal cnt_q : unsigned(9 downto 0); signal c_q : boolean; begin ----------------------------------------------------------------------------- -- Process seq -- -- Purpose: -- Implements the sequential elements: -- * timer counter -- * carry (underflow) marker flag -- seq: process (ck_i, por_i) begin if por_i then cnt_q <= (others => '1'); c_q <= false; elsif ck_i'event and ck_i = '1' then if icyc_en_i then if cnt_q = 0 then -- counter underflow: -- * reload counter -- * set marker flag cnt_q <= (others => '1'); c_q <= true; else cnt_q <= cnt_q - 1; end if; end if; if ck_en_i and op_i = SKIP_TIMER then c_q <= false; end if; end if; end process seq; -- ----------------------------------------------------------------------------- c_o <= c_q; end rtl; ------------------------------------------------------------------------------- -- File History: -- -- $Log: not supported by cvs2svn $ -------------------------------------------------------------------------------