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-- VHDL Entity R6502_TC.Reg_SP.symbol

--

-- Created:

--          by - eda.UNKNOWN (ENTWICKL4-XP-PR)

--          at - 19:48:44 17.04.2008

--

-- Generated by Mentor Graphics' HDL Designer(TM) 2007.1a (Build 13)

--

LIBRARY ieee;

USE ieee.std_logic_1164.all;

USE ieee.std_logic_arith.all;

entity Reg_SP is

   port(

      adr_i        : in     std_logic_vector (15 downto 0);

      clk_clk_i    : in     std_logic;

      ld_i         : in     std_logic_vector (1 downto 0);

      ld_sp_i      : in     std_logic;

      rst_rst_i    : in     std_logic;

      sel_sp_as_i  : in     std_logic;

      sel_sp_in_i  : in     std_logic;

      sel_sp_val_i : in     std_logic;

      adr_nxt_sp_o : out    std_logic_vector (15 downto 0);

      adr_sp_o     : out    std_logic_vector (15 downto 0)

   );

-- Declarations

end Reg_SP ;

-- Jens-D. Gutschmidt     Project:  R6502_TC  

-- scantara2003@yahoo.de                      

-- COPYRIGHT (C) 2008 by Jens Gutschmidt and OPENCORES.ORG                                                                                     

--                                                                                                                                             

-- This program is free software: you can redistribute it and/or modify it under the terms of the GNU General Public License as published by   

-- the Free Software Foundation, either version 3 of the License, or any later version.                                                        

--                                                                                                                                             

-- This program is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of              

-- MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License for more details.                                  

--                                                                                                                                             

-- You should have received a copy of the GNU General Public License along with this program.  If not, see <http://www.gnu.org/licenses/>.     

--                                                                                                                                             

-- CVS Revisins History                                                                                                                        

--                                                                                                                                             

-- $Log: not supported by cvs2svn $                                                                                                                                      

-- Title:  Stack Pointer Logic  

-- Path:  R6502_TC/Reg_SP/struct  

-- Edited:  by eda on 17 Apr 2008  

--

-- VHDL Architecture R6502_TC.Reg_SP.struct

--

-- Created:

--          by - eda.UNKNOWN (ENTWICKL4-XP-PR)

--          at - 19:48:45 17.04.2008

--

-- Generated by Mentor Graphics' HDL Designer(TM) 2007.1a (Build 13)

--

LIBRARY ieee;

USE ieee.std_logic_1164.all;

USE ieee.std_logic_arith.all;

architecture struct of Reg_SP is

   -- Architecture declarations

   -- Internal signal declarations

   signal d        : std_logic_vector(7 downto 0);

   signal dout1    : std_logic_vector(7 downto 0);

   signal dout2    : std_logic_vector(7 downto 0);

   signal dout3    : std_logic;

   signal load     : std_logic;

   signal load3    : std_logic;

   signal val_one  : std_logic_vector(7 downto 0);

   signal val_two  : std_logic_vector(7 downto 0);

   signal val_zero : std_logic_vector(7 downto 0);

   -- Implicit buffer signal declarations

   signal adr_sp_o_internal : std_logic_vector (15 downto 0);

   -- ModuleWare signal declarations(v1.9) for instance 'U_0' of 'adff'

   signal mw_U_0reg_cval : std_logic_vector(7 downto 0);

   -- ModuleWare signal declarations(v1.9) for instance 'U_4' of 'adff'

   signal mw_U_4reg_cval : std_logic_vector(7 downto 0);

begin

   -- Architecture concurrent statements

   -- HDL Embedded Text Block 2 eb2

   -- eb1 1

   val_zero (7 downto 0) <= X"00";

   val_one (7 downto 0) <= X"01";

   val_two (7 downto 0) <= X"02";

   adr_nxt_sp_o (15 downto 8) <= X"01";

   -- HDL Embedded Text Block 3 eb3

   -- eb1 1

   adr_nxt_sp_o (7 DOWNTO 0) <= d;

   -- ModuleWare code(v1.9) for instance 'U_11' of 'addsub'

   u_11combo_proc: process (adr_sp_o_internal(7 DOWNTO 0), dout1, dout3, val_zero(0))

   variable temp_din0 : std_logic_vector(8 downto 0);

   variable temp_din1 : std_logic_vector(8 downto 0);

   variable temp_sum : unsigned(8 downto 0);

   variable temp_carry : std_logic;

   begin

      temp_din0 := '0' & adr_sp_o_internal(7 DOWNTO 0);

      temp_din1 := '0' & dout1;

      temp_carry := val_zero(0);

      if (dout3 = '1') then

         temp_sum := unsigned(temp_din0) + unsigned(temp_din1) + temp_carry;

      else

         temp_sum := unsigned(temp_din0) - unsigned(temp_din1) - temp_carry;

      end if;

      dout2 <= conv_std_logic_vector(temp_sum(7 downto 0),8);

   end process u_11combo_proc;

   -- ModuleWare code(v1.9) for instance 'U_0' of 'adff'

   adr_sp_o_internal(7 DOWNTO 0) <= mw_U_0reg_cval;

   u_0seq_proc: process (clk_clk_i, rst_rst_i)

   begin

      if (rst_rst_i = '1') then

         mw_U_0reg_cval <= "00000000";

      elsif (clk_clk_i'event and clk_clk_i='1') then

         if (load = '1') then

            mw_U_0reg_cval <= d;

         end if;

      end if;

   end process u_0seq_proc;

   -- ModuleWare code(v1.9) for instance 'U_4' of 'adff'

   adr_sp_o_internal(15 DOWNTO 8) <= mw_U_4reg_cval;

   u_4seq_proc: process (clk_clk_i, rst_rst_i)

   begin

      if (rst_rst_i = '1') then

         mw_U_4reg_cval <= "00000000";

      elsif (clk_clk_i'event and clk_clk_i='1') then

         if (load3 = '1') then

            mw_U_4reg_cval <= val_one;

         end if;

      end if;

   end process u_4seq_proc;

   -- ModuleWare code(v1.9) for instance 'U_6' of 'and'

   load <= ld_sp_i and ld_i(0);

   -- ModuleWare code(v1.9) for instance 'U_7' of 'and'

   load3 <= ld_sp_i and ld_i(1);

   -- ModuleWare code(v1.9) for instance 'U_2' of 'inv'

   dout3 <= not(sel_sp_as_i);

   -- ModuleWare code(v1.9) for instance 'U_5' of 'mux'

   u_5combo_proc: process(val_one, val_two, sel_sp_val_i)

   begin

      case sel_sp_val_i is

      when '0' => dout1 <= val_one;

      when '1' => dout1 <= val_two;

      when others => dout1 <= (others => 'X');

      end case;

   end process u_5combo_proc;

   -- ModuleWare code(v1.9) for instance 'U_8' of 'mux'

   u_8combo_proc: process(dout2, adr_i(7 DOWNTO 0), sel_sp_in_i)

   begin

      case sel_sp_in_i is

      when '0' => d <= dout2;

      when '1' => d <= adr_i(7 DOWNTO 0);

      when others => d <= (others => 'X');

      end case;

   end process u_8combo_proc;

   -- Instance port mappings.

   -- Implicit buffered output assignments

   adr_sp_o <= adr_sp_o_internal;

end struct;