1 Oct
1998
1 Oct
'98
2:26 p.m.
OK, next question. While I look for weird expansion cards, is there
any book that I stand a chance at finding which details the DOS flopy
format?
from
> Hmmm... I don't know of one built
commercially, but how about a board
> based round an FPGA (for the non-hardware types, basically a
configurable
> chip that you can make just about any logic
circuit out of) linked to
an
> floppy drive. Oh, and some kind of programmable
clock (I don't think
> dividing down a master clock with the FPGA would really do it)/PLL
thingy
to act as a
read clock.
Overly complicated, no (hardware) PLL necessary. Just sample the data the drive at a sufficient multiple of the channel code
data rate (8x
should be
plenty), and do the data separation in software. That
way it really is
completely independent of the data format. That's the way I designed
my
closed-caption decoder (5x), and it works quite well.
Note that this doesn't deal with all of the weird Apple ][ copy
protection
schemes (like spiral tracks), but it will deal with
some of them.
I have a twiggy disks for the Lisa 1 with a bad sector. I've always
wondered
whether hacking the drive electronics to allow software
control over
the
read amplifier gain and/or data slice threshold would
let me recover
that
sector.
Cheers,
Eric
______________________________________________________
Get Your Private, Free Email at http://www.hotmail.com