Universal drive

From: Max Eskin <maxeskin_at_hotmail.com>
Date: Thu Oct 1 21:26:54 1998

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?
>> 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
from
>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
>
>

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Received on Thu Oct 01 1998 - 21:26:54 BST

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