Subversion Repositories System09

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

--                                                                             --

--  System09 - Synthesizable System On a Chip - VHDL FPGA core top level file. --

--                                                                             --

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

--

--

-- File name      : System09_Terasic_DE1.vhd

--

-- Entity name    : System09

--

-- Purpose        : Top level file for 6809 compatible system on a chip

--                  Designed with Alera EP2C20 Cyclone 2 FPGA.

--                  Implemented with Terasic DE1 FPGA board,

--

-- Dependencies   : ieee.Std_Logic_1164

--                  ieee.std_logic_unsigned

--                  ieee.std_logic_arith

--                  ieee.numeric_std

--

-- Uses           : cpu09         (..\VHDL\cpu09.vhd)              CPU core

--                  dat_ram       (..\VHDL\datram.vhd)             Dynamic Address Translation

--                  mon_rom       (..\Cyclone2\mon_rom.vhd)        Monitor ROM

--                  acia6850      (..\VHDL\acia6850.vhd)           ACIA (UART)

--                  ACIA_Clock    (..\VHDL\ACIA_Clock.vhd)         ACIA Baud Rate Clock Divider

--                  keyboard      (..\VHDL\keyboard.vhd)           PS/2 Keyboard register interface

--                  ps2_keyboard  (..\VHDL\ps2_keyboard.vhd)       PS/2 Keyboard interface logic

--                  keymap_rom    (..\Cyclone2\keymap_rom.vhd)     PS/2 Keyboard key code look up table

--                  vdu8          (..\VHDL\vdu8.vhd)                   Video Display Unit

--                                (..\Cyclone2\char_rom.vhd)       Character Generator ROM (B16_RAM)

--                                (..\Cyclone2\ram_2k.vhd)         Text & Attribute RAM Buffer

--                  seven_segment (..\VHDL\SevenSegment.vhd)       Seven Segment Display

--

-- Author         : John E. Kent

--                  dilbert57@opencores.org

--

-- Memory Map     :

--

-- $0000 - $DFFF System RAM (512K Mapped via DAT)

-- $E000 - ACIA (SWTPc)

-- $E010 - Reserved for SWTPc FD-01 FD1771 FDC

-- $E020 - Keyboard

-- $E030 - VDU

-- $E040 - Reserved for SWTPc MP-T (was Compact Flash)

-- $E050 - Timer

-- $E060 - Reserved for Bus Trap (Hardware Breakpoint Logic)

-- $E070 - Reserved for Trace Buffer

-- $E080 - Reserved for SWTPc MP-ID 6821 PIA (?)

-- $E090 - Reserved for SWTPc MP-ID 6840 PTM (?)

-- $E0A0 - Switches in / LEDS out

-- $E0B0 - 7 Segment hex display

-- $E0C0 - Reserved

-- $E0D0 - Reserved

-- $E0E0 - Reserved

-- $E0F0 - Reserved

-- $E100 - $E13F Reserved IDE / Compact Flash Card

-- $E140 - $E17F Reserved for Ethernet MAC (XESS)

-- $E180 - $E1BF Reserved for Expansion Slot 0 (XESS)

-- $E1C0 - $E1FF Reserved for Expansion Slot 1 (XESS)

-- $E200 - $EFFF Reserved for Future I/O

-- $F000 - $F7FF RAM for Sys09bug monitor extensions

-- $F800 - $FFFF Sys09bug ROM (Read only)

-- $FFF0 - $FFFF DAT - Dynamic Address Translation (Write Only)

--

--

--  Copyright (C) 2003 - 2010 John Kent

--

--  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 .

--

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

--

--                              Revision History:

--

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

--

-- Version 0.1 - 20 March 2003

-- Version 0.2 - 30 March 2003

-- Version 0.3 - 29 April 2003

-- Version 0.4 - 29 June 2003

--

-- Version 0.5 - 19 July 2003

-- prints out "Hello World"

--

-- Version 0.6 - 5 September 2003

-- Runs SBUG

--

-- Version 1.0- 6 Sep 2003 - John Kent

-- Inverted sys_clk

-- Initial release to Open Cores

--

-- Version 1.1 - 17 Jan 2004 - John Kent

-- Updated miniUart.

--

-- Version 1.2 - 25 Jan 2004 - John Kent

-- removed signals "test_alu" and "test_cc"

-- Trap hardware re-instated.

--

-- Version 1.3 - 11 Feb 2004 - John Kent

-- Designed forked off to produce System09_VDU

-- Added VDU component

--      VDU runs at 25MHz and divides the clock by 2 for the CPU

-- UART Runs at 57.6 Kbps

--

-- Version 2.0 - 2 September 2004 - John Kent

-- ported to Digilent Xilinx Spartan3 starter board

--      removed Compaact Flash and Trap Logic.

-- Replaced SBUG with KBug9s

--

-- Version 2.1 - 21 November 2006 - John Kent

-- Replaced KBug9s with Sys09bug 1.0

-- Inverted bottom nybble of DAT register outputs

-- Changed ROM & I/O decoding to be compatible with SWTPc

-- Upped the serial baud rate to 115.2 KBd

-- added multiple global clock buffers

-- (Uart would not operate correctly)

--

-- Version 2.2 - 22 December 2006 - John Kent

-- Increased CPU clock from 12.5MHz to 25 MHz.

-- Removed some of the global clock buffers

-- Added LED output register

-- Changed address decoding to 4K Blocks

--

-- Version 2.3 - 1 June 2007 - John Kent

-- Updated VDU & ACIA

-- Changed decoding for Sys09Bug

--

-- Version 2.4 - 31 January 2008 - John Kent

--      ACIA does not appear to work.

-- Made RAM OE and WE strobes synchonous to sys_clk

--

-- Version 2.5 - 23rd Feburary 2009 - John Kent

-- Implemented recommendation to remove vga_clk clock buffer

--

-- Version 2.6 - 5th september 2010 - John Kent

-- Renamed ACIA_6850 to acia6850

-- Updated generics on VDU8

-- Shortened the "keyboard" label

-- Fixed up address label on CPU09

-- Removed Flex RAM

-- Map RAM at $F000 - $F7FF

--

-- Vesrion 2.7 - 22nd October 2010 - John Kent

-- Ported from Digilent XC3S200 Starter to

-- Terasic EP2C20 DE1 board.

--

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

library ieee;

   use ieee.std_logic_1164.all;

   use IEEE.STD_LOGIC_ARITH.ALL;

   use IEEE.STD_LOGIC_UNSIGNED.ALL;

   use ieee.numeric_std.all;

entity System09_Terasic_DE1 is

  port(

        -- clocks

        clock_24    : in    std_logic_vector(1 downto 0);

        clock_27    : in    std_logic;

    clock_50    : in    std_logic;  -- System Clock input

    ext_clock   : in    std_logic;

    -- push button keys

        key         : in    std_logic_vector(3 downto 0);  -- RST, NMI

    -- SRAM interface signals

    sram_ce_n   : out   std_logic;

    sram_we_n   : out   std_logic;

    sram_oe_n   : out   std_logic;

        sram_ub_n   : out   std_logic;

        sram_lb_n   : out   std_logic;

    sram_addr   : out   std_logic_vector(17 downto 0);

    sram_dq     : inout std_logic_vector(15 downto 0);

        -- PS/2 Keyboard

        ps2_clk     : inout Std_logic;

        ps2_dat     : inout Std_Logic;

        -- ACIA/UART Interface

    uart_rxd    : in  Std_Logic;

        uart_txd    : out Std_Logic;

        -- CRTC output signals

    vga_r       : out std_logic_vector(3 downto 0);

    vga_g       : out std_logic_vector(3 downto 0);

    vga_b       : out std_logic_vector(3 downto 0);

    vga_hs      : out Std_Logic;

        vga_vs      : out Std_Logic;

        -- LEDS & Switches

        ledg        : out std_logic_vector(7 downto 0);

        ledr        : out std_logic_vector(9 downto 0);

        sw          : in  std_logic_vector(9 downto 0);

        -- hexadecimal display

        hex0        : out std_logic_vector(6 downto 0);

        hex1        : out std_logic_vector(6 downto 0);

        hex2        : out std_logic_vector(6 downto 0);

        hex3        : out std_logic_vector(6 downto 0);

        -- gnereal purpose I/O

        gpio_0      : in  std_logic_vector(35 downto 0);

        gpio_1      : in  std_logic_vector(35 downto 0);

        -- i2c interface

        i2c_sclk    : in std_logic;

        i2c_sdat    : in std_logic;

        -- audio codec

        aud_adcdat  : in std_logic;

        aud_adclrck : in std_logic;

        aud_bclk    : in std_logic;

        aud_dacdat  : in std_logic;

        aud_daclrck : in std_logic;

        aud_xck     : in std_logic;

        -- dram

        dram_addr  : out std_logic_vector(11 downto 0);

        dram_dq    : in  std_logic_vector(15 downto 0);

        dram_cs_n  : out std_logic;

        dram_ba_0  : in std_logic;

        dram_ba_1  : in std_logic;

        dram_ldqm  : in std_logic;

        dram_udqm  : in std_logic;

        dram_ras_n : out std_logic;

        dram_cas_n : out std_logic;

        dram_we_n  : out std_logic;

        dram_cke   : in std_logic;

        dram_clk   : in std_logic;

         -- Flash memory

        fl_addr    : out std_logic_vector(21 downto 0);

        fl_dq      : in  std_logic_vector(7 downto 0);

        fl_rst_n   : in  std_logic;

        fl_oe_n    : out std_logic;

        fl_we_n    : out std_logic;

        -- JTAG

        tck        : in std_logic;

        tcs        : in std_logic;

        tdi        : in std_logic;

        tdo        : in std_logic

        );

end System09_Terasic_DE1;

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

-- Architecture for System09

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

architecture my_computer of System09_Terasic_DE1 is

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

  -- constants

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

  constant SYS_CLK_FREQ  : integer := 50000000;  -- FPGA System Clock

  constant VGA_CLK_FREQ  : integer := 25000000;  -- VGA Pixel Clock

  constant CPU_CLK_FREQ  : integer := 25000000;  -- CPU Clock

  constant BAUD_Rate     : integer := 57600;      -- Baud Rate

  constant ACIA_CLK_FREQ : integer := BAUD_Rate * 16;

  type hold_state_type is ( hold_release_state, hold_request_state );

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

  -- Signals

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

  signal sys_clk       : std_logic;

  signal vga_clk       : std_logic;

  signal pll_locked    : std_logic;

  -- CPU Interface signals

  signal cpu_clk       : std_logic;

  signal cpu_rst       : std_logic;

  signal cpu_rw        : std_logic;

  signal cpu_vma       : std_logic;

  signal cpu_halt      : std_logic;

  signal cpu_hold      : std_logic;

  signal cpu_firq      : std_logic;

  signal cpu_irq       : std_logic;

  signal cpu_nmi       : std_logic;

  signal cpu_addr      : std_logic_vector(15 downto 0);

  signal cpu_data_in   : std_logic_vector(7 downto 0);

  signal cpu_data_out  : std_logic_vector(7 downto 0);

  -- Dynamic Address Translation

  signal dat_cs        : std_logic;

  signal dat_addr      : std_logic_vector(7 downto 0);

  -- BOOT ROM

  signal rom_cs        : Std_logic;

  signal rom_data_out  : Std_Logic_Vector(7 downto 0);

  -- ACIA Interface signals

  signal acia_clk      : std_logic;

  signal acia_cs       : Std_Logic;

  signal acia_data_out : Std_Logic_Vector(7 downto 0);

  signal acia_irq      : Std_Logic;

  signal acia_rxd      : Std_Logic;

  signal acia_txd      : Std_Logic;

  signal acia_dcd_n    : Std_Logic;

--  signal acia_rts_n    : Std_Logic;

  signal acia_cts_n    : Std_Logic;

  -- keyboard port

  signal kbd_data_out : std_logic_vector(7 downto 0);

  signal kbd_cs       : std_logic;

  signal kbd_irq      : std_logic;

  -- LEDs

  signal leds_data_out : std_logic_vector(7 downto 0);

  signal leds_cs       : std_logic;

  -- Video Display Unit

  signal vdu_cs       : std_logic;

  signal vdu_data_out : std_logic_vector(7 downto 0);

  signal vga_red      : std_logic;

  signal vga_green    : std_logic;

  signal vga_blue     : std_logic;

  -- LEDs

  signal led_cs       : std_logic;

  signal led_data_out : std_logic_vector(7 downto 0);

  -- 7 Segment Display

  signal hex_cs       : std_logic;

  signal hex_data_out : std_logic_vector(7 downto 0);

  signal hex0_reg     : std_logic_vector(7 downto 0);

  signal hex1_reg     : std_logic_vector(7 downto 0);

  signal hex2_reg     : std_logic_vector(7 downto 0);

  signal hex3_reg     : std_logic_vector(7 downto 0);

  -- interrupt timer

  signal tmr_data_out : std_logic_vector(7 downto 0);

  signal tmr_cs       : std_logic;

  signal tmr_irq      : std_logic;

  -- hardware break point (trap)

  signal hbp_data_out : std_logic_vector(7 downto 0);

  signal hbp_cs       : std_logic;

  signal hbp_irq      : std_logic;

  -- RAM

  signal sram_cs       : std_logic; -- memory chip select

  signal sram_data_out : std_logic_vector(7 downto 0);

  signal sram_ce       : std_logic;

  signal sram_ub       : std_logic;

  signal sram_lb       : std_logic;

  signal sram_we       : std_logic;

  signal sram_oe       : std_logic;

  -- System Clock Prescaler

  signal clk_count     : std_logic;

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

--

-- CPU09 CPU core

--

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

component cpu09

  port (

         clk      :     in  std_logic;

    rst      : in  std_logic;

    vma      :  out std_logic;

    addr     : out std_logic_vector(15 downto 0);

    rw       :  out std_logic;

    data_in  : in        std_logic_vector(7 downto 0);

         data_out : out std_logic_vector(7 downto 0);

         halt     : in  std_logic;

         hold     : in  std_logic;

         irq      : in  std_logic;

         nmi      : in  std_logic;

         firq     : in  std_logic

  );

end component;

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

--

-- Dynamic Address Translation Registers

--

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

component dat_ram

        port (

                clk      : in  std_logic;

                rst      : in  std_logic;

                cs       : in  std_logic;

                rw       : in  std_logic;

                addr_lo  : in  std_logic_vector(3 downto 0);

                addr_hi  : in  std_logic_vector(3 downto 0);

                data_in  : in  std_logic_vector(7 downto 0);

                data_out : out std_logic_vector(7 downto 0)

        );

end component;

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

--

-- 4KByte Block RAM Monitor ROM

--

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

component mon_rom

  Port (

    clk      : in  std_logic;

    rst      : in  std_logic;

    cs       : in  std_logic;

    rw       : in  std_logic;

    addr     : in  std_logic_vector (10 downto 0);

    data_in  : in  std_logic_vector (7 downto 0);

    data_out : out std_logic_vector (7 downto 0)

    );

end component;

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

--

-- 6850 ACIA

--

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

component acia6850

  port (

    clk      : in  Std_Logic;  -- System Clock

    rst      : in  Std_Logic;  -- Reset input (active high)

    cs       : in  Std_Logic;  -- ACIA Chip Select

    rw       : in  Std_Logic;  -- Read / Not Write

    addr     : in  Std_Logic;  -- Register Select

    data_in  : in  Std_Logic_Vector(7 downto 0); -- Data Bus In

    data_out : out Std_Logic_Vector(7 downto 0); -- Data Bus Out

    irq      : out Std_Logic;  -- Interrupt

    RxC      : in  Std_Logic;  -- Receive Baud Clock

    TxC      : in  Std_Logic;  -- Transmit Baud Clock

    RxD      : in  Std_Logic;  -- Receive Data

    TxD      : out Std_Logic;  -- Transmit Data

    DCD_n    : in  Std_Logic;  -- Data Carrier Detect

    CTS_n    : in  Std_Logic;  -- Clear To Send

    RTS_n    : out Std_Logic   -- Request To send

  );

end component;

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

--

-- ACIA Clock divider

--

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

component ACIA_Clock

  generic (

     SYS_CLK_FREQ  : integer :=  SYS_CLK_FREQ;

          ACIA_CLK_FREQ : integer := ACIA_CLK_FREQ

  );

  port (

     clk      : in  Std_Logic;  -- System Clock Input

          acia_clk : out Std_logic   -- ACIA Clock output

  );

end component;

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

--

-- PS/2 Keyboard

--

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

component keyboard

  generic(

    KBD_CLK_FREQ : integer := CPU_CLK_FREQ

  );

  port(

    clk             : in    std_logic;

    rst             : in    std_logic;

    cs              : in    std_logic;

    addr            : in    std_logic;

    rw              : in    std_logic;

    data_in         : in    std_logic_vector(7 downto 0);

    data_out        : out   std_logic_vector(7 downto 0);

    irq             : out   std_logic;

    kbd_clk         : inout std_logic;

    kbd_data        : inout std_logic

  );

end component;

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

--

-- Video Display Unit.

--

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

component vdu8

  generic(

    VGA_CLK_FREQ           : integer := VGA_CLK_FREQ; -- HZ

         VGA_HOR_CHARS          : integer := 80; -- CHARACTERS 25.6us

         VGA_HOR_CHAR_PIXELS    : integer := 8;  -- PIXELS 0.32us

         VGA_HOR_FRONT_PORCH    : integer := 16; -- PIXELS 0.64us

         VGA_HOR_SYNC           : integer := 96; -- PIXELS 3.84us

         VGA_HOR_BACK_PORCH     : integer := 48; -- PIXELS 1.92us

         VGA_VER_CHARS          : integer := 25; -- CHARACTERS 12.8ms

         VGA_VER_CHAR_LINES     : integer := 16; -- LINES 0.512ms

         VGA_VER_FRONT_PORCH    : integer := 10; -- LINES 0.320ms

         VGA_VER_SYNC           : integer := 2;  -- LINES 0.064ms

         VGA_VER_BACK_PORCH     : integer := 34  -- LINES 1.088ms

  );

  port(

    -- control register interface

    vdu_clk      : in  std_logic;        -- CPU Clock - 12.5MHz

    vdu_rst      : in  std_logic;

    vdu_cs       : in  std_logic;

    vdu_rw       : in  std_logic;

    vdu_addr     : in  std_logic_vector(2 downto 0);

    vdu_data_in  : in  std_logic_vector(7 downto 0);

    vdu_data_out : out std_logic_vector(7 downto 0);

    -- vga port connections

    vga_clk      : in  std_logic;       -- VGA Pixel Clock - 25 MHz

    vga_red_o    : out std_logic;

    vga_green_o  : out std_logic;

    vga_blue_o   : out std_logic;

    vga_hsync_o  : out std_logic;

    vga_vsync_o  : out std_logic

  );

end component;

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

--

-- Interrupt timer

--

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

component timer is

        port (

                clk        : in  std_logic;

                rst        : in  std_logic;

                cs         : in  std_logic;

                addr       : in  std_logic;

                rw         : in  std_logic;

                data_in    : in  std_logic_vector(7 downto 0);

                data_out   : out std_logic_vector(7 downto 0);

                irq        : out std_logic

        );

end component;

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

--

-- hardware break point (bus trap)

--

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

component trap is

        port (

                clk        : in  std_logic;

                rst        : in  std_logic;

                cs         : in  std_logic;

                rw         : in  std_logic;

                vma        : in  std_logic;

                addr       : in  std_logic_vector(15 downto 0);

                data_in    : in  std_logic_vector(7 downto 0);

                data_out   : out std_logic_vector(7 downto 0);

                irq        : out std_logic

        );

end component;

component pll IS

        PORT

        (

                areset          : IN STD_LOGIC  := '0';

                inclk0          : IN STD_LOGIC  := '0';

                c0                      : OUT STD_LOGIC ;

                c1                      : OUT STD_LOGIC ;

                c2                      : OUT STD_LOGIC ;

                locked          : OUT STD_LOGIC

        );

END component;

begin

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

  -- Instantiation of internal components

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

my_cpu : cpu09  port map (

         clk         => cpu_clk,

    rst       => cpu_rst,

    vma       => cpu_vma,

    addr      => cpu_addr(15 downto 0),

    rw       => cpu_rw,

    data_in   => cpu_data_in,

         data_out  => cpu_data_out,

         halt      => cpu_halt,

         hold      => cpu_hold,

         irq       => cpu_irq,

         nmi       => cpu_nmi,

         firq      => cpu_firq

    );

my_dat : dat_ram port map (

    clk       => cpu_clk,

        rst       => cpu_rst,

        cs        => dat_cs,

        addr_hi   => cpu_addr(15 downto 12),

        addr_lo   => cpu_addr(3 downto 0),

        rw        => cpu_rw,

        data_in   => cpu_data_out,

        data_out  => dat_addr(7 downto 0)

         );

my_rom : mon_rom port map (

    clk       => cpu_clk,

    rst       => cpu_rst,

        cs        => rom_cs,

        rw        => '1',

    addr      => cpu_addr(10 downto 0),

    data_in   => cpu_data_out,

    data_out  => rom_data_out

    );

my_acia  : acia6850 port map (

        clk           => cpu_clk,

        rst       => cpu_rst,

    cs        => acia_cs,

    addr      => cpu_addr(0),

        rw        => cpu_rw,

        data_in   => cpu_data_out,

        data_out  => acia_data_out,

    irq       => acia_irq,

        RxC       => acia_clk,

        TxC       => acia_clk,

        RxD       => acia_rxd,

        TxD       => acia_txd,

        DCD_n     => acia_dcd_n,

        CTS_n     => acia_cts_n,

        RTS_n     => open

    );

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

--

-- ACIA Clock

--

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

my_ACIA_Clock : ACIA_Clock

  generic map(

    SYS_CLK_FREQ  => SYS_CLK_FREQ,

         ACIA_CLK_FREQ => ACIA_CLK_FREQ

  )

  port map(

    clk        => sys_clk,

    acia_clk   => acia_clk

  );

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

--

-- PS/2 Keyboard Interface

--

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

my_keyboard : keyboard

   generic map (

          KBD_CLK_FREQ => CPU_CLK_FREQ

        )

   port map(

          clk          => cpu_clk,

          rst          => cpu_rst,

          cs           => kbd_cs,

          addr         => cpu_addr(0),

          rw           => cpu_rw,

          data_in      => cpu_data_out(7 downto 0),

          data_out     => kbd_data_out(7 downto 0),

          irq          => kbd_irq,

          kbd_clk      => ps2_clk,

          kbd_data     => ps2_dat

        );

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

--

-- Video Display Unit instantiation

--

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

my_vdu : vdu8

  generic map(

    VGA_CLK_FREQ           => VGA_CLK_FREQ, -- 25MHZ

    VGA_HOR_CHARS          => 80, -- CHARACTERS 25.6us

    VGA_HOR_CHAR_PIXELS    => 8,  -- PIXELS 0.32us

    VGA_HOR_FRONT_PORCH    => 16, -- PIXELS 0.64us

    VGA_HOR_SYNC           => 96, -- PIXELS 3.84us

    VGA_HOR_BACK_PORCH     => 48, -- PIXELS 1.92us

    VGA_VER_CHARS          => 25, -- CHARACTERS 12.8ms

    VGA_VER_CHAR_LINES     => 16, -- LINES 0.512ms

    VGA_VER_FRONT_PORCH    => 10, -- LINES 0.320ms

    VGA_VER_SYNC           => 2,  -- LINES 0.064ms

    VGA_VER_BACK_PORCH     => 34  -- LINES 1.088ms

  )

  port map(

    -- Control Registers

    vdu_clk       => cpu_clk,                                    -- 12.5 MHz System Clock in

    vdu_rst       => cpu_rst,

    vdu_cs        => vdu_cs,

    vdu_addr      => cpu_addr(2 downto 0),

    vdu_rw        => cpu_rw,

    vdu_data_in   => cpu_data_out,

    vdu_data_out  => vdu_data_out,

    -- vga port connections

    vga_clk       => vga_clk,                                    -- 25 MHz pixel clock

    vga_red_o     => vga_red,

    vga_green_o   => vga_green,

    vga_blue_o    => vga_blue,

    vga_hsync_o   => vga_hs,

    vga_vsync_o   => vga_vs

  );

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

--

-- Interrupt timer

--

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

my_timer : timer

        port map (

                clk        => cpu_clk,

                rst        => cpu_rst,

                cs         => tmr_cs,

                addr       => cpu_addr(0),

                rw         => cpu_rw,

                data_in    => cpu_data_out,

                data_out   => tmr_data_out,

                irq        => tmr_irq

        );

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

--

-- hardware break point (bus trap)

--

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

my_hw_bp : trap

        port map (

                clk        => cpu_clk,

                rst        => cpu_rst,

                cs         => hbp_cs,

                rw         => cpu_rw,

                vma        => cpu_vma,

                addr       => cpu_addr,

                data_in    => cpu_data_out,

                data_out   => hbp_data_out,

                irq        => hbp_irq

        );

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

--

-- Phase Locked Loop Clock divider

--

my_pll : pll

        PORT MAP

        (

                areset          => '0',

                inclk0          => clock_50,

                c0                      => sys_clk,

                c1                      => cpu_clk,

                c2                      => vga_clk,

                locked          => pll_locked

        );

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

--

-- Process to decode memory map

--

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

mem_decode: process( cpu_addr, cpu_rw, cpu_vma,

                                        dat_cs, dat_addr,

                                        rom_data_out,

                                        acia_data_out,

                                        kbd_data_out,

                                        vdu_data_out,

                                        hex_data_out,

                                        led_data_out,

                                        tmr_data_out,

                                        hbp_data_out,

                                        sram_data_out

                                        )

begin

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

      dat_cs      <= '0';

      rom_cs      <= '0';

      acia_cs     <= '0';

      kbd_cs      <= '0';

      vdu_cs      <= '0';

      hex_cs      <= '0';

      led_cs      <= '0';

      sram_cs     <= '0';

          tmr_cs      <= '0';

      hbp_cs      <= '0';

--          pb_cs       <= '0';

--      ide_cs      <= '0';

--      ether_cs    <= '0';

--          slot1_cs    <= '0';

--      slot2_cs    <= '0';

      if cpu_addr( 15 downto 8 ) = "11111111" then

            cpu_data_in <= rom_data_out;

        dat_cs      <= cpu_vma;              -- write DAT

        rom_cs      <= cpu_vma;              -- read  ROM

            --

                -- Sys09Bug Monitor ROM $F000 - $FFFF

                --

           elsif dat_addr(3 downto 0) = "1111" then -- $XF000 - $XFFFF

          if cpu_addr(11) = '1' then

            --

                    -- Monitor ROM $F800 - $FFFF

                    --

            cpu_data_in <= rom_data_out;

            rom_cs      <= cpu_vma;          -- read  ROM

          else

            --

                    -- SRAM $F000 - $F7FF

                    --

            cpu_data_in <= sram_data_out;

            sram_cs      <= cpu_vma;

          end if;

        --

                -- IO Devices $E000 - $EFFF

                --

                elsif dat_addr(3 downto 0) = "1110" then -- $XE000 - $XEFFF

                        case cpu_addr(11 downto 8) is

                        --

                        -- SWTPC peripherals from $E000 to $E0FF

                        --

                        when "0000" =>

                      case cpu_addr(7 downto 4) is

                          --

                          -- ACIA ($E000 - $E00F)

                          --

                          when "0000" =>

                        cpu_data_in <= acia_data_out;

                            acia_cs      <= cpu_vma;

                  --

                          -- Reserved - FD1771 FDC ($E010 - $E01F) (SWTPC)

              --

                          --

              -- Keyboard port ($E020 - $E02F)

                          --

                          when "0010" =>

                cpu_data_in <= kbd_data_out;

                            kbd_cs      <= cpu_vma;

              --

              -- VDU port ($E030 - $E03F)

                          --

                          when "0011" =>

                cpu_data_in <= vdu_data_out;

                            vdu_cs      <= cpu_vma;

              --

                          -- Reserved - SWTPc MP-T ($E040 - $E04F)

                          --

              --

              -- Reserved - Timer ($E050 - $E05F) (B5-X300)

                          --

                          when "0101" =>

                            cpu_data_in <= tmr_data_out;

                            tmr_cs      <= cpu_vma;

              --

              -- Reserved - hardware break point (Bus Trap) ($E060 - $E06F)

                          --

                          when "0110" =>

                            cpu_data_in <= hbp_data_out;

                            hbp_cs      <= cpu_vma;

              --

              -- Reserved - I/O port ($E070 - $E07F) (B5-X300)

                          --

                          --

                          -- Reserved - PTM 6840 ($E080 - $E08F) (SWTPC)

                          --

                          --

                          -- Reserved - PIA Timer ($E090 - $E09F) (SWTPC)

                          --

              --

                          -- Read Switched port ($E0A0 - $E0AF)

                          -- Write LEDS

                          --

                          when "1010" =>

                cpu_data_in <= led_data_out;

                            led_cs     <= cpu_vma;

              --

              -- 7 segment display port ($E0B0 - $E0BF)

                          --

                          when "1011" =>

                cpu_data_in <= hex_data_out;

                            hex_cs      <= cpu_vma;

                          when others => -- $EXC0 to $EXFF

                            null;

                      end case;

            --

                        --      $E100 to $EFFF reserved for future use

                        --

                when others =>

                          null;

         end case;

                --

                -- Everything else is RAM

                --

                else

                  cpu_data_in <= sram_data_out;

                  sram_cs      <= cpu_vma;

    end if;

end process;

--

-- 1M byte SRAM Control

-- Processes to read and write memory based on bus signals

--

sram_process: process( sys_clk, cpu_rst,

                      cpu_addr, cpu_rw, cpu_vma, cpu_data_out,

                                          dat_addr, sram_cs,

                      sram_ce,  sram_ub, sram_lb, sram_dq,

                                          sram_we,  sram_oe )

begin

    --

        -- Clock Hold on rising edge

        --

    if( sys_clk'event and sys_clk='1' ) then

                --

                -- sram_hold signal helps