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