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------------------------------------------------------------------

--      6502 Top module.

--

--      Copyright Ian Chapman October 28 2010

--      email author@kool.kor

--      author  EQU     ichapman

--      kool    EQU     videotron

--      kor     EQU     ca

--      ******************************************************

--      Dec 12 2010

--      RAM increased to 2k 0 to $7ff for bigger test code

--      sta irq and sta nmi trigger interrupts

--      ******************************************************

--      This file is part of the Lattice 6502 project  

--      It is used to compile with ispLeaver not Linux ghdl.

--      It is the address mapping and connecting the other modules.

--      It is replaced by Processor.vhd when running ispLeaver.

--

--      To do

--              This will be work in process or replaced whatever

--              project file is needed to control other modules.

--

--      *************************************************************

--      Distributed under the GNU Lesser General Public License.    *

--      This can be obtained from “www.gnu.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

--      (at your option) 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/>

--

--      Processor.vhd

------------------------------------------------------------------

--      Revision history

--      Nov 411, 2010

--      To facilitate testing of NMI and IRQ.

--      changed from I/O pins to signals

--      IRQ and NMI address decoded so as to initiated the inerupt from

------------------------------------------------------------------

library IEEE;                   --Use standard IEEE libs as recommended by Tristan. 

use IEEE.STD_LOGIC_1164.ALL;

use IEEE.numeric_std.all;

entity Processor is

Port (

--      data_wr : inout unsigned(7 downto 0);

        clk_pin : in std_logic;

--      clk_out : out std_logic;

--      u802 : out std_logic;

--      u702 : out std_logic;

--      u602 : out std_logic;

--      u1101 : out std_logic;  

--      u801 : out std_logic;

--      u701 : out std_logic;

        u601 : out std_logic;

        rst_pin : in std_logic;

--      irq_pin : in std_logic; --disabled to test interrupts on fpga

--      nmi_pin : in std_logic;

        RX_pin  : in std_logic;

--      PG_pin  : in std_logic;

        TX_pin  : out std_logic;

        Pwr_on_pin : out std_logic

    );

end Processor;

architecture structure of Processor is

--      COMPONENT DECLARATIONS

component P65C02

port(

        data_rd: in unsigned(7 downto 0);

        data_wr: out unsigned(7 downto 0);

--      cycle_mark : out std_logic;                     --Used to signal the cycle usually cycle 0.

        address: inout unsigned(15 downto 0);

        proc_write : inout std_logic;

        reset, clock : in std_logic;

        irq : in std_logic;

        nmi : in std_logic);

end component;

component UART_RX is

port(

        PG, OSC_10MHz,RX,  csr_usart :in std_logic;

        RX_rdy : out std_logic;

        rx_reg : out unsigned(7 downto 0)

        );

end component;

component UART_TX is

port(

        OSC_10MHz, PG, csw_usart :in std_logic;

        tx_dat : in unsigned(7 downto 0);

        TX ,tx_rdy : out std_logic

        );

end component;

component Lattice_rom

port (

        OutClock: in  std_logic;

        OutClockEn: in  std_logic;

        Reset: in  std_logic;

        Address: in  std_logic_vector(9 downto 0);

        Q: out  std_logic_vector(7 downto 0));

end component;

component Lattice_ram

port (

        Clock: in  std_logic;

        ClockEn: in  std_logic;

        Reset: in  std_logic;

        WE: in  std_logic;

        Address: in  std_logic_vector(10 downto 0);

        Data: in  std_logic_vector(7 downto 0);

        Q: out  std_logic_vector(7 downto 0));

end component;

--component ghdl_rom

--port  (

--      rom_dat: out unsigned(7 downto 0);

--      wr, clk, rst: in std_logic;

--      address: in unsigned(15 downto 0)

--    );

--end component;

--component ghdl_ram

--port  (

--      ram_dat: out unsigned(7 downto 0);

--      data_wr : in unsigned(7 downto 0);

--      clk, wr, rst: in std_logic;

--      address: in unsigned(15 downto 0)

--      );

--end component;

------------------------------------------------------------------------

-- Signal Declarations

------------------------------------------------------------------------

signal address : unsigned(15 downto 0);

signal add : unsigned(15 downto 0);

signal proc_rd_dat, rom_dat, ram_dat, data_wr : unsigned(7 downto 0);

signal rx_dat : unsigned(7 downto 0);

signal proc_write : std_logic;

signal one, RX_rdy, csw_usart, csr_usart, tx_rdy : std_logic;

signal rst_bar : std_logic;

signal clk : std_logic;

--signal clk_pin : std_logic;

signal counter : unsigned(3 downto 0);

signal ram_write : std_logic;

signal irq_pin, nmi_pin : std_logic;

--      I/O ports

--constant      led_port        : unsigned (15 downto 0) := x"4007";

constant        irq             : unsigned (15 downto 0) := X"4002";

constant        nmi             : unsigned (15 downto 0) := x"4003";

constant        rs232_dat   : unsigned (15 downto 0) := x"4000"; --input and output

constant        uart_stat   : unsigned (15 downto 0) := x"4001"; --RX and TX state found here

constant        uart: unsigned (15 downto 0) := x"4000"; --starts the uart transmitting

begin

U1 : P65C02 port map(

        reset => rst_pin,

        Clock => clk_pin,

        data_rd => proc_rd_dat,

        data_wr => data_wr,

        address => address,

        proc_write => proc_write,

        irq => irq_pin,

--      cycle_mark => cycle_mark);

        nmi => nmi_pin);

U2 : UART_RX port map (

        PG => rst_pin,

        OSC_10MHz => clk_pin,

        RX => RX_pin,

        rx_reg =>  rx_dat,

        csr_usart => csr_usart,

        RX_rdy => RX_rdy);

U3 : UART_TX port map (

        PG => rst_pin,

        TX => TX_pin,

        tx_rdy => tx_rdy,

        OSC_10MHz => clk_pin,

        tx_dat => data_wr,

        csw_usart => csw_usart);

--R1 : ghdl_rom port map(

--      rom_dat=>rom_dat,

--      address=>address,

--      wr=>proc_write,

--      clk=>clk_pin,

--      rst=>rst_pin);

--R2 : ghdl_ram port map(

--      clk=>clk_pin,

--      rst=>rst_pin,

--      ram_dat=>ram_dat,

--      data_wr=>data_wr,

--      address=>address,

--      wr=>ram_write);

R3 : Lattice_rom port map(

        Reset => rst_bar,

        OutClock => clk_pin,

        (address(9 downto 0)) => std_logic_vector(Address(9 downto 0)),

        unsigned(Q)  => rom_dat,

        OutClockEn => one);

R4 : Lattice_ram port map(

        Reset => rst_bar,

        Clock => clk_pin,

        WE => ram_write,

        address(10 downto 0) => std_logic_vector(Address(10 downto 0)),

        Data => std_logic_vector(data_wr),

        unsigned(Q) => ram_dat, ClockEn => one);

--      address(9 downto 0) => (Address(9 downto 0)), 

--      Data => (data_wr),

--      (Q) => ram_dat, ClockEn => one);

one <= '1';

rst_bar <= not rst_pin;

one <= '1';

--ram_write <= proc_write and not address(15) and not address(14) and not address(13) and not address(12) and not address(11) and not address(10);

--ram_write <= proc_write and not address(15) and not address(14);

--irq_pin <= '1';       --only used to test interrupts on fpga

--nmi_pin <= '1';

--u601 <= cycle_mark;

mux_add : process(rst_pin, clk_pin)

begin

if rst_pin = '0' then

add <= (others => '0');

elsif rising_edge(clk_pin) then

        add <= address;

end if;

end process;

ram_address : process (proc_write, address(15 downto 14))

begin

        if proc_write = '1' and address(15 downto 14) = "00" then

                ram_write <= '1';

        else

                ram_write <= '0';

        end if;

end process;

--      ===================================================================

--      Updated muxer process

muxer : process (add(15 downto 14), rom_dat, ram_dat, rx_dat, tx_rdy, rx_rdy)

begin

if add(15 downto 14) = "11" then

        proc_rd_dat <= rom_dat;

end if;

if add(15 downto 14) = "00" then

        proc_rd_dat <= ram_dat;

end if;

if add(15 downto 0) = rs232_dat then

        proc_rd_dat <= rx_dat;

end if;

if add(15 downto 0) = uart_stat then

        proc_rd_dat <= tx_rdy & rx_rdy & "000000";

end if;

end process;

--      ===================================================================

rs232_cs : process (rst_pin, clk_pin, address, proc_write)

begin

if proc_write = '0' and address = uart then

        csr_usart <= '1';

else

        csr_usart <= '0';

end if;

if proc_write = '1' and address = uart then

        csw_usart <= '1';

else

        csw_usart <= '0';

end if;

end process;

--      Only uded to test interrupts in the fpga

--      These two processe let the SW fire NMI and IRG

--      with a sta instruction.

irq : process (rst_pin, proc_write, address, data_wr(0), clk_pin)

begin

if rst_pin = '0' then

        irq_pin <= '1';

        elsif rising_edge(clk_pin) then

                if address = irq and proc_write = '1' then

                        irq_pin <= data_wr(0);   --set and hold bit 0

                end if;

end if;

end process;

nmi : process (rst_pin, proc_write, address, data_wr(0), clk_pin)

begin

if rst_pin = '0' then

        nmi_pin <= '1';

        elsif rising_edge(clk_pin) then

                if address = nmi and proc_write = '1' then

                        nmi_pin <= data_wr(0);   --set and hold bit 0

                end if;

end if;

end process;

--relay : process (rst_pin, proc_write, address, data_wr(7), clk_pin)

--begin

--if rst_pin = '0' then

--      Pwr_on_pin <= '0';

--      elsif rising_edge(clk_pin) and address = led_port  and proc_write = '1' then

--      Pwr_on_pin <= data_wr(7);

--end if;

--end process;

end structure;