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------------------------------------------------------------------------------- -- -- The Program Memory control unit. -- All operations related to the Program Memory are managed here. -- -- $Id: pmem_ctrl.vhd,v 1.5 2005-06-11 10:08:43 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.pmem_addr_t; use work.t48_pack.word_t; use work.t48_pmem_ctrl_pack.pmem_addr_ident_t; entity t48_pmem_ctrl is port ( -- Global Interface ------------------------------------------------------- clk_i : in std_logic; res_i : in std_logic; en_clk_i : in boolean; -- T48 Bus Interface ------------------------------------------------------ data_i : in word_t; data_o : out word_t; write_pcl_i : in boolean; read_pcl_i : in boolean; write_pch_i : in boolean; read_pch_i : in boolean; inc_pc_i : in boolean; write_pmem_addr_i : in boolean; addr_type_i : in pmem_addr_ident_t; read_pmem_i : in boolean; -- Porgram Memroy Interface ----------------------------------------------- pmem_addr_o : out pmem_addr_t; pmem_data_i : in word_t ); end t48_pmem_ctrl; library ieee; use ieee.numeric_std.all; use work.t48_pmem_ctrl_pack.all; use work.t48_pack.res_active_c; use work.t48_pack.clk_active_c; use work.t48_pack.bus_idle_level_c; use work.t48_pack.pmem_addr_width_c; use work.t48_pack.dmem_addr_width_c; use work.t48_pack.page_t; architecture rtl of t48_pmem_ctrl is -- implemented counter width of Program Counter -- the upper bit is only altered by JMP, CALL and RET(R) subtype pc_count_range_t is natural range pmem_addr_width_c-2 downto 0; -- the Program Counter signal program_counter_q : unsigned(pmem_addr_t'range); -- the Program Memory address signal pmem_addr_s, pmem_addr_q : std_logic_vector(pmem_addr_t'range); begin ----------------------------------------------------------------------------- -- Process program_counter -- -- Purpose: -- Implements the Program Counter. -- program_counter: process (res_i, clk_i) begin if res_i = res_active_c then program_counter_q <= (others => '0'); pmem_addr_q <= (others => '0'); elsif clk_i'event and clk_i = clk_active_c then if en_clk_i then -- parallel load mode if write_pcl_i then program_counter_q(data_i'range) <= UNSIGNED(data_i); elsif write_pch_i then program_counter_q(pmem_addr_width_c-1 downto data_i'high+1) <= UNSIGNED(data_i(pmem_addr_width_c - dmem_addr_width_c - 1 downto 0)); elsif inc_pc_i then -- increment mode -- the MSB is not modified by linear increments -- it can only be altered by JMP, CALL or RET(R) program_counter_q(pc_count_range_t) <= program_counter_q(pc_count_range_t) + 1; end if; -- set pmem address if write_pmem_addr_i then pmem_addr_q <= pmem_addr_s; end if; end if; end if; end process program_counter; -- ----------------------------------------------------------------------------- ----------------------------------------------------------------------------- -- Process pmem_addr -- -- Purpose: -- Multiplex the Program Memory address. -- pmem_addr: process (program_counter_q, addr_type_i, pmem_addr_q, data_i) begin -- default assignment pmem_addr_s <= STD_LOGIC_VECTOR(program_counter_q); case addr_type_i is when PM_PC => -- default is ok null; when PM_PAGE => pmem_addr_s(word_t'range) <= data_i; -- take page address from program counter -- => important for JMPP, MOVP! -- they must wrap to next page when at FF! when PM_PAGE3 => pmem_addr_s(word_t'range) <= data_i; -- page address is explicitely specified pmem_addr_s(page_t'range) <= "0011"; when others => null; end case; end process pmem_addr; -- ----------------------------------------------------------------------------- ----------------------------------------------------------------------------- -- Process data_output -- -- Purpose: -- Multiplex the data bus output. -- data_output: process (read_pmem_i, read_pcl_i, read_pch_i, pmem_data_i, program_counter_q) begin data_o <= (others => bus_idle_level_c); if read_pmem_i then data_o <= pmem_data_i; elsif read_pcl_i then data_o <= STD_LOGIC_VECTOR(program_counter_q(data_o'range)); elsif read_pch_i then data_o(3 downto 0) <= STD_LOGIC_VECTOR(program_counter_q(pmem_addr_width_c-1 downto data_o'high+1)); end if; end process data_output; -- ----------------------------------------------------------------------------- ----------------------------------------------------------------------------- -- Output Mapping. ----------------------------------------------------------------------------- pmem_addr_o <= pmem_addr_q; end rtl; ------------------------------------------------------------------------------- -- File History: -- -- $Log: not supported by cvs2svn $ -- Revision 1.4 2005/06/08 19:13:53 arniml -- fix bug report -- "MSB of Program Counter changed upon PC increment" -- -- Revision 1.3 2004/07/11 16:51:33 arniml -- cleanup copyright notice -- -- Revision 1.2 2004/04/24 23:44:25 arniml -- move from std_logic_arith to numeric_std -- -- Revision 1.1 2004/03/23 21:31:53 arniml -- initial check-in -- -------------------------------------------------------------------------------