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-- VHDL Entity R6502_TC.Reg_PC.symbol
--
-- Created:
--          by - eda.UNKNOWN (ENTWICKL4-XP-PR)
--          at - 22:53:05 04.01.2009
--
-- 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_PC 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_pc_i      : in     std_logic;
      offset_i     : in     std_logic_vector (15 downto 0);
      rst_rst_n_i  : in     std_logic;
      sel_pc_as_i  : in     std_logic;
      sel_pc_in_i  : in     std_logic;
      sel_pc_val_i : in     std_logic_vector (1 downto 0);
      adr_nxt_pc_o : out    std_logic_vector (15 downto 0);
      adr_pc_o     : out    std_logic_vector (15 downto 0)
   );
 
-- Declarations
 
end Reg_PC ;
 
-- 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 $                                                                                                                         
--   <<-- more -->>                                                                                                                            
-- Title:  Program Counter Logic  
-- Path:  R6502_TC/Reg_PC/struct  
-- Edited:  by eda on 01 Jan 2009  
--
-- VHDL Architecture R6502_TC.Reg_PC.struct
--
-- Created:
--          by - eda.UNKNOWN (ENTWICKL4-XP-PR)
--          at - 22:53:06 04.01.2009
--
-- 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_PC is
 
   -- Architecture declarations
 
   -- Internal signal declarations
   signal adr_pc_high_o_i : std_logic_vector(7 downto 0);
   signal adr_pc_low_o_i  : std_logic_vector(7 downto 0);
   signal adr_pc_o_i      : std_logic_vector(15 downto 0);
   signal as_n_o_i        : std_logic;
   signal ci_o_i          : std_logic;
   signal cout_pc_o_i     : std_logic;
   signal load3_o_i       : std_logic;
   signal load_o_i        : std_logic;
   signal offset_high_o_i : std_logic_vector(7 downto 0);
   signal offset_low_o_i  : std_logic_vector(7 downto 0);
   signal val_o_i         : std_logic_vector(7 downto 0);
   signal val_one         : std_logic_vector(7 downto 0);
   signal val_zero        : std_logic_vector(7 downto 0);
 
   -- Implicit buffer signal declarations
   signal adr_pc_o_internal     : std_logic_vector (15 downto 0);
   signal adr_nxt_pc_o_internal : std_logic_vector (15 downto 0);
 
 
   -- ModuleWare signal declarations(v1.9) for instance 'U_11' of 'addsub'
   signal mw_U_11temp_din0 : std_logic_vector(8 downto 0);
   signal mw_U_11temp_din1 : std_logic_vector(8 downto 0);
   signal mw_U_11sum : unsigned(8 downto 0);
 
   -- ModuleWare signal declarations(v1.9) for instance 'U_12' of 'addsub'
   signal mw_U_12temp_din0 : std_logic_vector(8 downto 0);
   signal mw_U_12temp_din1 : std_logic_vector(8 downto 0);
   signal mw_U_12sum : unsigned(8 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
 
   -- ModuleWare code(v1.9) for instance 'U_11' of 'addsub'
   mw_U_11temp_din0 <= '0' & adr_pc_low_o_i;
   mw_U_11temp_din1 <= '0' & val_o_i;
   u_11combo_proc: process (mw_U_11temp_din0, mw_U_11temp_din1, as_n_o_i)
   variable temp_carry : std_logic;
   begin
      temp_carry := '0';
      if (as_n_o_i = '1') then
         mw_U_11sum <= unsigned(mw_U_11temp_din0) + unsigned(mw_U_11temp_din1) + temp_carry;
      else
         mw_U_11sum <= unsigned(mw_U_11temp_din0) - unsigned(mw_U_11temp_din1) - temp_carry;
      end if;
   end process u_11combo_proc;
   adr_nxt_pc_o_internal(7 DOWNTO 0) <= conv_std_logic_vector(mw_U_11sum(7 downto 0),8);
   cout_pc_o_i <= mw_U_11sum(8);
 
   -- ModuleWare code(v1.9) for instance 'U_12' of 'addsub'
   mw_U_12temp_din0 <= '0' & adr_pc_high_o_i;
   mw_U_12temp_din1 <= '0' & offset_high_o_i;
   u_12combo_proc: process (mw_U_12temp_din0, mw_U_12temp_din1, as_n_o_i, ci_o_i)
   variable temp_carry : std_logic;
   begin
      temp_carry := ci_o_i;
      if (as_n_o_i = '1') then
         mw_U_12sum <= unsigned(mw_U_12temp_din0) + unsigned(mw_U_12temp_din1) + temp_carry;
      else
         mw_U_12sum <= unsigned(mw_U_12temp_din0) - unsigned(mw_U_12temp_din1) - temp_carry;
      end if;
   end process u_12combo_proc;
   adr_nxt_pc_o_internal(15 DOWNTO 8) <= conv_std_logic_vector(mw_U_12sum(7 downto 0),8);
 
   -- ModuleWare code(v1.9) for instance 'U_0' of 'adff'
   adr_pc_o_internal(7 DOWNTO 0) <= mw_U_0reg_cval;
   u_0seq_proc: process (clk_clk_i, rst_rst_n_i)
   begin
      if (rst_rst_n_i = '0') then
         mw_U_0reg_cval <= "00000000";
      elsif (clk_clk_i'event and clk_clk_i='1') then
         if (load_o_i = '1') then
            mw_U_0reg_cval <= adr_nxt_pc_o_internal(7 DOWNTO 0);
         end if;
      end if;
   end process u_0seq_proc;
 
   -- ModuleWare code(v1.9) for instance 'U_4' of 'adff'
   adr_pc_o_internal(15 DOWNTO 8) <= mw_U_4reg_cval;
   u_4seq_proc: process (clk_clk_i, rst_rst_n_i)
   begin
      if (rst_rst_n_i = '0') then
         mw_U_4reg_cval <= "00000000";
      elsif (clk_clk_i'event and clk_clk_i='1') then
         if (load3_o_i = '1') then
            mw_U_4reg_cval <= adr_nxt_pc_o_internal(15 DOWNTO 8);
         end if;
      end if;
   end process u_4seq_proc;
 
   -- ModuleWare code(v1.9) for instance 'U_6' of 'and'
   load_o_i <= ld_pc_i and ld_i(0);
 
   -- ModuleWare code(v1.9) for instance 'U_7' of 'and'
   load3_o_i <= ld_pc_i and ld_i(1);
 
   -- ModuleWare code(v1.9) for instance 'U_10' of 'and'
   ci_o_i <= cout_pc_o_i and ld_pc_i;
 
   -- ModuleWare code(v1.9) for instance 'U_1' of 'constval'
   val_zero <= "00000000";
 
   -- ModuleWare code(v1.9) for instance 'U_9' of 'constval'
   val_one <= "00000001";
 
   -- ModuleWare code(v1.9) for instance 'U_2' of 'inv'
   as_n_o_i <= not(sel_pc_as_i);
 
   -- ModuleWare code(v1.9) for instance 'U_8' of 'mux'
   u_8combo_proc: process(adr_pc_o_internal, adr_i, sel_pc_in_i)
   begin
      case sel_pc_in_i is
      when '0' => adr_pc_o_i <= adr_pc_o_internal;
      when '1' => adr_pc_o_i <= adr_i;
      when others => adr_pc_o_i <= (others => 'X');
      end case;
   end process u_8combo_proc;
 
   -- ModuleWare code(v1.9) for instance 'U_13' of 'mux'
   u_13combo_proc: process(val_one, val_zero, offset_low_o_i, 
                           sel_pc_val_i)
   begin
      case sel_pc_val_i is
      when "00" => val_o_i <= val_one;
      when "01" => val_o_i <= val_zero;
      when "10" => val_o_i <= offset_low_o_i;
      when "11" => val_o_i <= val_zero;
      when others => val_o_i <= (others => 'X');
      end case;
   end process u_13combo_proc;
 
   -- ModuleWare code(v1.9) for instance 'U_3' of 'split'
   adr_pc_low_o_i <= adr_pc_o_i(7 downto 0);
   adr_pc_high_o_i <= adr_pc_o_i(15 downto 8);
 
   -- ModuleWare code(v1.9) for instance 'U_5' of 'split'
   offset_low_o_i <= offset_i(7 downto 0);
   offset_high_o_i <= offset_i(15 downto 8);
 
   -- Instance port mappings.
 
   -- Implicit buffered output assignments
   adr_pc_o     <= adr_pc_o_internal;
   adr_nxt_pc_o <= adr_nxt_pc_o_internal;
 
end struct;