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[/] [t48/] [tags/] [rel_1_1/] [rtl/] [vhdl/] [dmem_ctrl.vhd] - Rev 289
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------------------------------------------------------------------------------- -- -- The Data Memory control unit. -- All accesses to the Data Memory are managed here. -- -- $Id: dmem_ctrl.vhd,v 1.5 2006-06-20 01:07:16 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.dmem_addr_t; use work.t48_pack.word_t; use work.t48_dmem_ctrl_pack.dmem_addr_ident_t; entity t48_dmem_ctrl is port ( -- Global Interface ------------------------------------------------------- clk_i : in std_logic; res_i : in std_logic; en_clk_i : in boolean; -- Control Interface ------------------------------------------------------ data_i : in word_t; write_dmem_addr_i : in boolean; write_dmem_i : in boolean; read_dmem_i : in boolean; addr_type_i : in dmem_addr_ident_t; bank_select_i : in std_logic; data_o : out word_t; -- Data Memory Interface -------------------------------------------------- dmem_data_i : in word_t; dmem_addr_o : out dmem_addr_t; dmem_we_o : out std_logic; dmem_data_o : out word_t ); end t48_dmem_ctrl; library ieee; use ieee.numeric_std.all; use work.t48_pack.clk_active_c; use work.t48_pack.res_active_c; use work.t48_pack.bus_idle_level_c; use work.t48_pack.to_stdLogic; use work.t48_dmem_ctrl_pack.all; architecture rtl of t48_dmem_ctrl is signal dmem_addr_s, dmem_addr_q : dmem_addr_t; begin ----------------------------------------------------------------------------- -- Process addr_decode -- -- Purpose: -- Decode/multiplex the address information for the Data Memory. -- addr_decode: process (data_i, addr_type_i, bank_select_i, dmem_addr_q) variable stack_addr_v : unsigned(5 downto 0); begin -- default assignment dmem_addr_s <= dmem_addr_q; stack_addr_v := (others => '0'); case addr_type_i is when DM_PLAIN => dmem_addr_s <= data_i; when DM_REG => dmem_addr_s <= (others => '0'); dmem_addr_s(2 downto 0) <= data_i(2 downto 0); -- implement bank switching if bank_select_i = '1' then -- dmem address 24 - 31: access proper set dmem_addr_s(4 downto 3) <= "11"; end if; when DM_STACK => -- build address from stack pointer stack_addr_v(3 downto 1) := unsigned(data_i(2 downto 0)); -- dmem address 8 - 23 stack_addr_v := stack_addr_v + 8; dmem_addr_s <= (others => '0'); dmem_addr_s(5 downto 0) <= std_logic_vector(stack_addr_v); when DM_STACK_HIGH => dmem_addr_s(0) <= '1'; when others => -- do nothing -- pragma translate_off assert false report "Unknown address type identification for Data Memory controller!" severity error; -- pragma translate_on end case; end process addr_decode; -- ----------------------------------------------------------------------------- ----------------------------------------------------------------------------- -- Process dmem_addr_reg -- -- Purpose: -- Implements the Data Memory Address Register. -- This register is required to hold the address during a write operation -- as we cannot hold the address in the input register of the -- synchronous RAM (no clock suppression/gating). -- -- NOTE: May be obsoleted by clock enable feature of generic RTL RAM. -- dmem_addr_reg: process (res_i, clk_i) begin if res_i = res_active_c then dmem_addr_q <= (others => '0'); elsif clk_i'event and clk_i = clk_active_c then if en_clk_i then if write_dmem_addr_i then dmem_addr_q <= dmem_addr_s; end if; end if; end if; end process dmem_addr_reg; -- ----------------------------------------------------------------------------- ----------------------------------------------------------------------------- -- Output mapping. ----------------------------------------------------------------------------- dmem_addr_o <= dmem_addr_s when write_dmem_addr_i and en_clk_i else dmem_addr_q; -- data from bus is fed through dmem_data_o <= data_i; -- data to bus is enabled upon read request data_o <= dmem_data_i when read_dmem_i else (others => bus_idle_level_c); -- write enable to Data Memory is fed through dmem_we_o <= to_stdLogic(write_dmem_i); end rtl; ------------------------------------------------------------------------------- -- File History: -- -- $Log: not supported by cvs2svn $ -- Revision 1.4 2005/06/11 10:08:43 arniml -- introduce prefix 't48_' for all packages, entities and configurations -- -- Revision 1.3 2004/04/24 23:44:25 arniml -- move from std_logic_arith to numeric_std -- -- Revision 1.2 2004/04/18 18:58:29 arniml -- clean up sensitivity list -- -- Revision 1.1 2004/03/23 21:31:52 arniml -- initial check-in -- -------------------------------------------------------------------------------
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