Compared to the tape, this is really simple.  Cartridges are emulated
    by files of 137923 bytes.  These files have the extension .MDR, and can
    contain up to 126K of data.  The emulator emulates 8 microdrives, the
    maximum amount the Interface I software can handle, and each of these
    cartridge files can be inserted in any of the 8 microdrives.  (Do not
    insert one file into more than one microdrive; this will cause problems
    with the buffering done by the emulator as well as the Interface I, and
    might result in data loss).

    Press F8 to enter the microdrive menu.  Press 1 to 8 to select a
    microdrive, and I to insert a microdrive cartridge.  You can select an
    existing one, or type a new name.  If the cartridge file isn't found,
    the emulator asks whether it should create it.  When created, you'll
    have to format it first; if you don't, you'll get a 'microdrive not
    present' error when you try to read it, just as happens with real
    unformatted cartridges.  To format a cartridge, type

        FORMAT "m";1;"name"

    After this the cartridge should have 126K of free space.

    The cartridge can be write protected; see the menu option in the F8
    menu.  This is a characteristic of the cartridge, and the write protect
    tab information is therefore stored in the cartridge file.

    As on the real Spectrum, you'll have to be careful with OUT's if a
    cartridge is inserted.  Try OUT 239,0 (on a real Spectrum, this turns
    on the microdrive motor) and wait a few seconds; most of your data will
    be lost!  You can stop the microdrive motor by typing STOP (or, more
    generally, generate an error).

    The microdrives are emulated at IN/OUT level.  This means that every
    utility or program that uses microdrives ought to work on the emulator.
    Most utilities use hook codes, and these will certainly work.

    The GAP line is emulated; this signal is activated if the interface I
    senses a piece of tape with no data on it.  If the checksum of the
    first header block of a microdrive header or data block is not correct,
    that block is considered to be a GAP.  This will only happen if some
    utility writes a bad block to microdrive deliberately, if the file is
    newly created and unformatted, or when you type OUT 239,0.

    To try the microdrive, load a Spectrum program, switch to Spectrum
    48K+If.1 mode if necessary, and turn on Multiface 128 emulation.  Press
    F8, I(nsert cartridge), enter some file name and create an unformatted
    cartridge, return to the Spectrum and press F5 (NMI), S(ave), enter
    some name, choose M(icrodrive), choose F(ormat) and wait a few seconds,
    then choose S(ave).  Then reset the Spectrum, and type LOAD
    *"m";1;"name" to re-load the snapshot you just made.

    Alternatively, switch to SamRam mode, make sure a formatted cartridge
    is present, press F5, S, M, S, name, and press ENTER twice to have the
    SamRam save a snapshot to microdrive.  This snapshot can only be loaded
    in SamRam mode.