Date   : Tue, 23 Nov 2010 01:23:42 +0000
From   : jgh@... (J.G.Harston)
Subject: Harddisc fakery using a microcontroller

Rick Murray wrote:
> nowadays. I wanted to write an emulator (which is sort of in limbo at
> the moment) to look at hacking the firmware to permit an SD card to be
> used off the parallel port, as a form of storage.

What you want is a hard drive equivalent of this:
http://hxc2001.free.fr/floppy_drive_emulator

As far as the system it is plugged into is concerned, it looks like
a floppy drive and quacks like a floppy drive. What you need is the
equivalent that quacks like a SCSI hard drive.

> As a possible alternative, is it viable for a small embedded MCU to
> work with the DOS filesystem? If so, without overly complicating
> things, perhaps work using "images"?

The above directs all "disk accesses" to data read/writes in image
files held in a FAT formatted SD card. For instance "step out to
track zero" becomes ptr=0 within the emulator. "step in one track"
becomes ptr=ptr+(sec_per_track)*(byte_per_sec), etc.

-- 
J.G.Harston - jgh@...