7 May
2007
7 May
'07
2:10 a.m.
Jules Richardson wrote:
Hmm, any chance of making the connector more of a CPU
bus, with a
handful of address lines? Then you just plug in a little module, one per
floppy drive, to give that drive an ID on the bus.
Sounds like a good plan.
Adding stuff like that isn't hard - because the CPLD only handles read, write
and indexing, everything else (drive selection, density select output, motor
on/off signalling, basically everything that doesn't need fantastically
accurate timing) is handled by a microcontroller. Adding more I/Os at TTL
level is just a case of adding more links from the MCU to the output ports.
The big problem is that this is going to add an extra connector to the drive
interface box...
My thinking is that supporting just two drive types
isn't enough in a
general archive box, and even four might not cut it. The only overhead
is a data cable per floppy drive, and a few buffer / address decoding
ICs...
Would eight drives be enough for you, or would you prefer sixteen? :)
Open-collector or TTL outputs?
The module would have a standard 34 pin connector for
drive signals on
it, or I suppose there might be special-case variants for 8" or for some
really oddball setups.
What I don't want to end up doing is designing something that needs a box full
of addon modules to use, or becomes useless if those modules are lost. The
plan is to build something that can handle 80% of the work as-is, then do the
other 20% with the help of AOMs.
(I was tempted to say you could make the modules plug
straight into the
back of the drives, similar to SCSI SCA adapters, and then just have a
single bus cable connecting them all up, but the lack of any standard as
to placement of a floppy drive's data connector makes that problematic)
So use an IDC header or something, have the board push into the drive, then
have a flylead connecting up the power.
Did I mention USB didn't have enough oomph to power the CPLD, MCU *and* a disc
drive as well? You're going to need a 5V + 12V + whatever PSU for the drive,
but the box itself will snaffle power from the laptop/desktop machine you've
got it hooked up to.
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