DS81
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                           Copyright 2006 Ian Cowburn
                              ianc@noddybox.co.uk


1. LICENSE
----------

    The code to DS81 is released under the GNU General Public License.  See
    the text file COPYING for details.

    Other included software is provided in good faith, is not released under
    the GNU General Public License, and is copyright their respective authors.
    If any of these authors disagree with the distribution of their work then
    contact me and it will be gladly removed.

        ZX81 BASIC ROM (c) 1981 Nine Tiles Networks LTD
        3D Monster Maze (c) 1983 Malcom E. Evans
        Mazogs, City Patrol and Sabotage (c) 1981, 1982 Don Priestley


2. ZX81
-------

    The ZX81 was an 8-bit computer released by Sinclair Research in 1981, using
    the Z80 CPU.
    
    It was a monochrome machine with no sound (be quiet those at the back of
    the room who used to be able to do sound by doing odd things with the video
    signal) and a text mode that could be used to plot graphics at a resolution
    of 64 by 44 (hmmm, smaller than most icons nowadays).

    It came with 1K of RAM, though most people opted for a massive 16K RAM pack.


2. DS81
-------

    DS81 is an emulation of the 16K ZX81 and is is supplied in two main forms,
    as a native Nintendo DS executable and a version with a Gameboy Advance
    wrapper (in case your Ninentdo DS homebrew device only supports running
    GBA executables).
    
    In addition to this two different versions are supplied, one which
    initialises the FAT library and one which doesn't.  They are identical save
    for this, and separate ones are supplied in case the FAT library
    initialisation causes problem on your homebrew device:

        ds81.nds          - Nintendo DS version
        ds81.bs.gba       - As above with a GBA wrapper.

        ds81-nofat.nds    - Nintendo DS version; no FAT library initialisation.
        ds81-nofat.bs.gba - As above with a GBA wrapper.

    I'm probably being overly paranoid there, but better safe than sorry.


3. Using DS81
-------------

    When run DS81 displays a splash screen with copyright information and
    whether the FAT library has been able to find a supported device for the
    loading of external tapes.

    Once the A button has been pressed the ZX81 resets and displays itself
    on the top screen, and a soft keyboard is displayed on the bottom, touch
    sensitive, DS screen.
    
    If you've never used a ZX81 before then you may wish to find out how the
    keyboard works -- it uses a keyword entry system, rather than the straight
    typing if commands.  So, for instance, the key P is pressed to enter PRINT
    when the cursor is in keyword mode (the cursor in an inverted K).

    Trust me; you were glad of it when using the original ZX81's hard plastic
    membrane keyboard.

    When using the soft keyboard by default the shift key is 'sticky' and once
    used will stay held down until pressed again.

    The World of Spectrum has the original ZX81 manuals, either as a PDF
    or in HTML form:

        http://www.worldofspectrum.org/

    At the bottom of the keyboard is an area where you can click to bring up a
    menu.  Either use the stylus, or the joypad and button A to select an
    option from the following choices:

        RESET ZX81     
            This resets the emulated ZX81.

        SELECT TAPE     
            Selects the built-in tape to use (DS81 has a number of ZX81 tapes
            built into it).  The next section has extra information on the
            loading of games.

        STICK SHIFT ON
            Sets the shift key so it stays down until pressed again.

        STICK SHIFT OFF
            Sets the shift key so it behaves likes all the other keys.

        MAP JOYPAD TO KEYS
            Allows you to redefine the DS's joypad and buttons to ZX81 keys.
            Follow the on-screen instructions.

        CANCEL
            Cancels the menu.



3. Using the internal tapes on DS81
-----------------------------------

    Games on the ZX81 were supplied on cassette.  DS81 includes a few tape
    files that are selectable from the menu.  Follow the on-screen instructions
    to select the game.  A quick description and the controls to use are
    displayed on the top screen.

    Once you've selected a tape you can load it in the emulator by using the
    command LOAD "".  If you're really stuck with the ZX81 keyboard:

        1. Select your tape.
        2. Reset the ZX81 from the menu.
        3. When the inverse K cursor is displayed press the J key to generate
           the keyword LOAD.
        4. Press the SHIFT key.
        5. Press the P key twice to enter the double quotes (DON'T use the
           double quotes got by pressing SHIFT+Q.  These are not the same!)
        6. Release the SHIFT key and press the NEW LINE key.
        7. The tape will load and run.


3. Using external tapes on DS81
-------------------------------

    If you are using the version of DS81 that allows the use of FAT devices,
    and you device is supported, they you can load any old tape.

    Simply place the .P file (ZX81 games are usually distributed as .P files
    that are simply an image of the memory that would have been dumped to tape)
    and either put it in the root directory of the FAT device or in a directory
    called ZX81SNAP.

    Note that currently hi-resolution games will not work.  For that matter,
    it can't be at all guaranteed that all original ZX81 games will work as
    expected.  After all, DS81 isn't really a ZX81.


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$Id$

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