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------------------------------------------------------------------------------- -- -- The Program Status Word (PSW). -- Implements the PSW with its special bits. -- -- $Id: psw.vhd,v 1.7 2004-07-11 16:51:33 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; entity psw 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; read_psw_i : in boolean; read_sp_i : in boolean; write_psw_i : in boolean; write_sp_i : in boolean; -- Decoder Interface ------------------------------------------------------ special_data_i : in std_logic; inc_stackp_i : in boolean; dec_stackp_i : in boolean; write_carry_i : in boolean; write_aux_carry_i : in boolean; write_f0_i : in boolean; write_bs_i : in boolean; carry_o : out std_logic; aux_carry_i : in std_logic; aux_carry_o : out std_logic; f0_o : out std_logic; bs_o : out std_logic ); end psw; 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.nibble_t; architecture rtl of psw is -- special bit positions in PSW constant carry_c : natural := 3; constant aux_carry_c : natural := 2; constant f0_c : natural := 1; constant bs_c : natural := 0; -- the PSW register signal psw_q : nibble_t; -- the Stack Pointer signal sp_q : unsigned(2 downto 0); -- pragma translate_off signal psw_s : word_t; -- pragma translate_on begin ----------------------------------------------------------------------------- -- Process psw_reg -- -- Purpose: -- Implements the PSW register. -- psw_reg: process (res_i, clk_i) begin if res_i = res_active_c then psw_q <= (others => '0'); sp_q <= (others => '0'); elsif clk_i'event and clk_i = clk_active_c then if en_clk_i then -- T48 bus access if write_psw_i then psw_q <= data_i(7 downto 4); end if; if write_sp_i then sp_q <= unsigned(data_i(2 downto 0)); end if; -- increment Stack Pointer if inc_stackp_i then sp_q <= sp_q + 1; end if; -- decrement Stack Pointer if dec_stackp_i then sp_q <= sp_q - 1; end if; -- access to special bits if write_carry_i then psw_q(carry_c) <= special_data_i; end if; -- if write_aux_carry_i then psw_q(aux_carry_c) <= aux_carry_i; end if; -- if write_f0_i then psw_q(f0_c) <= special_data_i; end if; -- if write_bs_i then psw_q(bs_c) <= special_data_i; end if; end if; end if; end process psw_reg; -- ----------------------------------------------------------------------------- ----------------------------------------------------------------------------- -- Process data_out -- -- Purpose: -- Output multiplexer for T48 Data Bus. -- data_out: process (read_psw_i, read_sp_i, psw_q, sp_q) begin data_o <= (others => bus_idle_level_c); if read_psw_i then data_o(7 downto 4) <= psw_q; end if; if read_sp_i then data_o(3 downto 0) <= '1' & std_logic_vector(sp_q); end if; end process data_out; -- ----------------------------------------------------------------------------- -- pragma translate_off tb: process (psw_q, sp_q) begin psw_s(7 downto 4) <= psw_q; psw_s(3) <= '1'; psw_s(2 downto 0) <= std_logic_vector(sp_q); end process tb; -- pragma translate_on ----------------------------------------------------------------------------- -- Output mapping. ----------------------------------------------------------------------------- carry_o <= psw_q(carry_c); aux_carry_o <= psw_q(aux_carry_c); f0_o <= psw_q(f0_c); bs_o <= psw_q(bs_c); end rtl; ------------------------------------------------------------------------------- -- File History: -- -- $Log: not supported by cvs2svn $ -- Revision 1.6 2004/04/24 23:44:25 arniml -- move from std_logic_arith to numeric_std -- -- Revision 1.5 2004/04/24 11:25:39 arniml -- removed dummy_s - workaround not longer needed for GHDL 0.11.1 -- -- Revision 1.4 2004/04/18 18:59:01 arniml -- add temporary workaround for GHDL 0.11 -- -- Revision 1.3 2004/04/04 14:15:45 arniml -- add dump_compare support -- -- Revision 1.2 2004/03/28 21:28:13 arniml -- take auxiliary carry from direct ALU connection -- -- Revision 1.1 2004/03/23 21:31:53 arniml -- initial check-in -- -------------------------------------------------------------------------------