floppy drive interface specifications

Yes, you should.

"Rene Tschaggelar" schreef in bericht news:44538522$0$13570$ snipped-for-privacy@news.sunrise.ch...

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

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.

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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.

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

ECMA appears to be linked to the C# language.

Rene

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.

Thomas

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.

Dimiter

------------------------------------------------------ Dimiter Popoff Transgalactic Instruments

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Rene Tschaggelar wrote:

ftp://ftp.beg-buerkle.de/support/Hersteller/Floppy/FD235HF/FD235HF-A429.pdf and the datasheet for the nec uPD765 and WD37C65 or other more recent controlers should get you going.

Best Regards

Steve Sousa

Here you have some in-depth specifications:

5.25" and 3.5" doesn't differ interface wise.

Here's the pinout:

Pay attention to these signals: Select drive Head select Enable motor Step direction Step signal Read data Track-0

What is the objective .. ?

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

Rene

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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).

ftp://ftp.beg-buerkle.de/support/Hersteller/Floppy/FD235HF/FD235HF-A429.pdf

Add the spec for an old 8277 or a more current 82077 for more complete CPU interfacing options.

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JosephKK
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Let me think about that a bit longer. I'll report back in due time.

Rene

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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.

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