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floppy drive interface specifications

Discussion in 'Electronic Design' started by Rene Tschaggelar, Apr 29, 2006.

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  1. I tried the manufacturers and wasn't able to
    find them there. The floppy drive interface
    specifications. To connect a floppy to an embedded
    system, I should have the pin descriptions, their
    function and timing. How and what commands are

  2. Fred Bloggs

    Fred Bloggs Guest

    Yes, you should.
  3. Rene,

    There has been an ECMA specification concerning this information. Ever had
    it in my hands but can't find it anymore. Maybe yo can google for it.

    petrus bitbyter
  4. Nico Coesel

    Nico Coesel Guest

    A floppy drive doesn't understand commands. The signals to and from a
    floppy drive are very basic. You'll need a floppy drive controller
    chip to do something usefull with a floppy drive. A good starting
    point is to look into PC style hardware. Depending on your
    requirements, you might be able to salvage a controller chip from an
    old XT or AT floppy controller board.
  5. Guest

    Not really an answer to your question, but I'd strongly recommend
    considering some sort of flash memory card instead of a floppy for any
    new application.

    3.5" floppy disks are notoriously unrelable, not perhaps originally,
    but because both the drives and the media have been cost optomized to
    the point where they can't be reliable. You could buy a very high
    quality drive, and still end up with a customer using dirt cheap media.
    Plus they're big, they're magnets for dust, they're slow, they don't
    sotre much, etc...

    Only if trying to make a drop in replacement for an existing product
    with a strong "tradition" around it would I think a mechanical floppy
    drive would make sense, and even then I'd be tempted to push the
    switch, if necessary lashing together some sort of legacy (parallel or
    serial port) reader to work with older PC's.
  6. Guest

    I have the IBM tech ref for the original IBM PC and the PS/2. I could
    copy the pages for you. It has the command set and the actual
    schematics for the original PC adapter
    My address is good

  7. ECMA appears to be linked to the C# language.

  8. Zak

    Zak Guest

    Look for the wd1771/wd179x data sheets. There may be an even older
    version that has an even better data sheet.

    The drive interface has stuff like data in, data out (the host should do
    the encoding/decoding), stepping pulses (to move the head), an indicator
    when the head is on track 0, whenever the media rotates through its
    index position. From there it is timing, reading sector marks, reding
    the data (or switching to write to start writing).

    The wd17xx equivalent should be on the system using the floppy drive.
    The floppy drive is just a buch of motors with drivers and a head with
    drivers and read amp.

  9. Didi

    Didi Guest

    To connect a floppy to an embedded
    I can find the connector in my old projects from the 80-s,
    I could plot them to a .gif or .pdf file for you - but I will
    have to do some digging. Please make sure you want to
    connect an old style FDD - it has no controller, you
    need a NEC uPD765 or equivalent (well, there were
    also other chips but this one made it through the years
    in various IP forms), and write some code driving
    heads/sides, implementing seek commands by counting
    stepper pulses, etc. I did it twice during the 80-s, but
    by todays standards this may seem too much work...
    You may wish to consider one of these $15 or so
    USB floppy drives they sell for notebooks, will definitely
    be the easier to do option (I would guess they are like ATAPI
    drives over USB, perhaps SFF-8070).
    If you decide you really do need the schematics of my old
    FDD interface which has the connector shown on it,
    let me know and I'll start digging.

  10. Steve Sousa

    Steve Sousa Guest
    and the datasheet for the nec uPD765 and WD37C65 or other more recent
    controlers should get you going.

    Best Regards

    Steve Sousa
  11. Thanks, that should start me going.
    The objective is to create a floppy drive. Not a
    magnetic one though

  12. Guest

    What is the objective .. ?
    What would be the benefit of this one over what's already "out there" ..?

    Beware that I haven't seen any floppy controller doing more than 2 Mbps.
    Thus a lowend storage media (pc floppy controller is braindead ontop of that).
  13. joseph2k

    joseph2k Guest

    Add the spec for an old 8277 or a more current 82077 for more complete CPU
    interfacing options.
  14. Let me think about that a bit longer.
    I'll report back in due time.

  15. Mark Zenier

    Mark Zenier Guest

    Here's some stuff I dug up a few years back when I was thinking
    about a project for an SPI interfaced floppy controller for
    low end embedded projects.

    There are ISO standards for the format, with specs for the CRC and
    stuff like that, if you need to have the simulator interpet the
    data stream (track/sector and stuff like that).

    ANSI X3.80-1988 the physical drive interface, (some strange
    obselete stuff in there). I got better information from the
    National PC8477B super FDC controller chip datasheet.

    ISO 7487/3 360 kbyte (MS-DOS) Double Sided Double Density disk format

    ISO 8378/1 720 kbyte 5 1/4" disks media description
    ISO 8378/2 seldom used standard format
    ISO 8378/3 format used by MS-DOS
    ISO 8630/1 1.2 Meg 5 1/4 inch media
    ISO 8630/2 seldom used standard format
    ISO 8630/3 format used by MS-DOS
    ISO 9529/1 3.5 inch media
    ISO 9529/2 1.44 Meg format

    A couple of other items that look useful that are in my notes
    are Motorola Application Note AN917 about their analog floppy
    read/write ICs , and and article in Computer Design for February 1980.

    The main wierdness that you'd have to deal with is that the controllers
    predistort the timing of pulses to compensate for bit time shifts
    caused by bit crowding on the media. So if your drive simulator amounts
    to a dumb logic analyzer, (just saving the bit stream), you'd need to
    compensate for this predistortion and then save each bit transition time
    with a resolution of (SWAG) 10 nanoseconds or so. (The controller
    derives the read timing with a PLL, so if the bit timing is too coarse,
    it might FUBAR).

    What happened to my project? Well, I copied all of my floppy media to
    images on a CD ROM so I didn't need to read them again, and found in
    doing that, (like another poster said), that 3.5 inch media are now such
    crap that they're not longer worth the effort.

    Mark Zenier
    Googleproofaddress(account:mzenier provider:eskimo domain:com)
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