Info on UM8397 floppy disk IC?

From: Tony Duell <ard_at_p850ug1.demon.co.uk>
Date: Fri Dec 26 17:32:30 2003

>
> Hi,
>
> has anyone got any data on the UM8297 floppy disk controller IC?

Do you mean UM8397 (as in the Subject: line) ? If so, I probably have the
data sheet around here.

IIRC, this is an XT-class disk controller (250kbps data rate) and works
with 360K and 720K drives only. There was another chip (8398?) that was
an AT-class controller. I fitted that chip to an XT multi-I/O card that
used the 8397, fiddled the clock oscillator (IIRC, the 8397 uses an 8MHz
clock, the 9398 uses a 24MHz clock), and tiwddled the address lines to
put it at a non-standard address (these chips have intenral address
decoders). That's how I linked 8" drives to an XT...

>
> I found one on a tiny ISA board in the loft the other day (labelled
> "FDC-III"). I was hoping it might provide a little more flexibility in
> reading non-PC floppies on a PC machine (specifically Acorn BBC - none

I have never got either UMC chip to read single-density (FM) floppies.
Acorn DFS disks are, IIRC, single-density. ADFS disks may be double
density, and are easier to read on a PC.


> of the spare PC motherboards I have kicking around happen to have floppy
> controller ICs that do this)
>
> Using the ISA board in a PC with the on-board floppy disk controller
> disabled, the drives seek on startup as expected but I can't get any
> data from floppies put into them (known-good MSDOS-format disks,
> known-good drives, and a known-good data cable). Tried using both DOS
> and Linux.

What sort of drives and disks?

> 3) The chip might need some specific setup from DOS before it'll work
> correctly.

It doesn't. If it's the chip I am thinking of, it's a completely
compatible XT controller on a chip.

>
> 4) The chip might be expecting a specific floppy drive type or types to
> be attached, or set up in a certain way. I've only tried known-good high
> density 5.25" and 3.5" drives so far.

Aha... that's the problem. Try double-density (360K, 720K) drives and disks.

> 7406 chips, and some clock circuitry. No configuration on the board
> whatsoever.

There's very little you can configure in hardware with this chip.
Although there is an input pin to select between the 'normal' and
'alternate' FDC addresses.

-tony
Received on Fri Dec 26 2003 - 17:32:30 GMT