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------------------------------------------------------------------------------- -- -- The Timer/Counter unit. -- -- $Id: timer.vhd,v 1.7 2006-11-30 14:31:59 arniml Exp $ -- -- Copyright (c) 2004, 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/t48/ -- ------------------------------------------------------------------------------- library ieee; use ieee.std_logic_1164.all; use work.t48_pack.word_t; use work.t48_pack.mstate_t; entity t48_timer is generic ( -- state in which T1 is sampled (3 or 4) sample_t1_state_g : integer := 4 ); port ( -- Global Interface ------------------------------------------------------- clk_i : in std_logic; res_i : in std_logic; en_clk_i : in boolean; t1_i : in std_logic; clk_mstate_i : in mstate_t; -- T48 Bus Interface ------------------------------------------------------ data_i : in word_t; data_o : out word_t; read_timer_i : in boolean; write_timer_i : in boolean; -- Decoder Interface ------------------------------------------------------ start_t_i : in boolean; start_cnt_i : in boolean; stop_tcnt_i : in boolean; overflow_o : out std_logic ); end t48_timer; library ieee; use ieee.numeric_std.all; use work.t48_pack.all; architecture rtl of t48_timer is -- the 8 bit counter core signal counter_q : unsigned(word_t'range); signal overflow_q : boolean; -- increment signal for the counter core type inc_type_t is (NONE, TIMER, COUNTER); signal increment_s : boolean; signal inc_sel_q : inc_type_t; -- T1 edge detector signal t1_q : std_logic; signal t1_inc_s : boolean; -- timer prescaler signal prescaler_q : unsigned(4 downto 0); signal pre_inc_s : boolean; begin ----------------------------------------------------------------------------- -- Verify the generics ----------------------------------------------------------------------------- -- pragma translate_off assert (sample_t1_state_g = 3) or (sample_t1_state_g = 4) report "sample_t1_state_g must be either 3 or 4!" severity failure; -- pragma translate_on ----------------------------------------------------------------------------- -- Process t1_edge -- -- Purpose: -- Implements the edge detector for T1. -- t1_edge: process (t1_i, t1_q, clk_mstate_i) begin t1_inc_s <= false; -- sample in state according to generic -- Old devices: sample at the beginning of state 3 -- New devices: sample in state 4 if (sample_t1_state_g = 3 and clk_mstate_i = MSTATE3) or (sample_t1_state_g = 4 and clk_mstate_i = MSTATE4) then -- detect falling edge if t1_q = '1' and t1_i = '0' then t1_inc_s <= true; end if; end if; end process t1_edge; -- ----------------------------------------------------------------------------- pre_inc_s <= clk_mstate_i = MSTATE4 and prescaler_q = 31; ----------------------------------------------------------------------------- -- Process inc_sel -- -- Purpose: -- Select increment source (timer, counter or none). -- inc_sel: process (inc_sel_q, pre_inc_s, t1_inc_s) begin -- default assignment increment_s <= false; case inc_sel_q is when NONE => increment_s <= false; when TIMER => increment_s <= pre_inc_s; when COUNTER => increment_s <= t1_inc_s; when others => null; end case; end process inc_sel; -- ----------------------------------------------------------------------------- ----------------------------------------------------------------------------- -- Process regs -- -- Purpose: -- Implements the counter, the prescaler and other registers. -- regs: process (res_i, clk_i) begin if res_i = res_active_c then overflow_q <= false; t1_q <= '0'; prescaler_q <= (others => '0'); inc_sel_q <= NONE; counter_q <= (others => '0'); elsif clk_i'event and clk_i = clk_active_c then if en_clk_i then -- Counter Core and overflow ------------------------------------------ overflow_q <= false; if write_timer_i then counter_q <= unsigned(data_i); elsif increment_s then counter_q <= counter_q + 1; if counter_q = 255 then overflow_q <= true; end if; end if; -- T1 edge detector --------------------------------------------------- if (sample_t1_state_g = 3 and clk_mstate_i = MSTATE3) or (sample_t1_state_g = 4 and clk_mstate_i = MSTATE4) then t1_q <= t1_i; end if; -- Prescaler ---------------------------------------------------------- if start_t_i then prescaler_q <= (others => '0'); elsif clk_mstate_i = MSTATE3 then prescaler_q <= prescaler_q + 1; end if; -- Increment Selector ------------------------------------------------- if start_t_i then inc_sel_q <= TIMER; elsif start_cnt_i then inc_sel_q <= COUNTER; elsif stop_tcnt_i then inc_sel_q <= NONE; end if; end if; end if; end process regs; -- ----------------------------------------------------------------------------- ----------------------------------------------------------------------------- -- Output Mapping. ----------------------------------------------------------------------------- data_o <= std_logic_vector(counter_q) when read_timer_i else (others => bus_idle_level_c); overflow_o <= to_stdLogic(overflow_q); end rtl; ------------------------------------------------------------------------------- -- File History: -- -- $Log: not supported by cvs2svn $ -- Revision 1.6 2005/06/11 10:08:43 arniml -- introduce prefix 't48_' for all packages, entities and configurations -- -- Revision 1.5 2004/07/11 16:51:33 arniml -- cleanup copyright notice -- -- Revision 1.4 2004/07/04 13:06:45 arniml -- counter_q is not cleared during reset -- this would match all different descriptions of the Counter as -- a) if the software assumes that the Counter is modified during reset, it -- will initialize the Counter anyhow -- b) the special case 'Counter not modified during reset' is covered -- -- Revision 1.3 2004/05/16 15:32:57 arniml -- fix edge detector bug for counter -- -- Revision 1.2 2004/04/15 22:05:13 arniml -- increment prescaler with MSTATE4 -- -- Revision 1.1 2004/03/23 21:31:53 arniml -- initial check-in -- -------------------------------------------------------------------------------