26 Dec
2003
26 Dec
'03
9:32 a.m.
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