Path: utzoo!attcan!uunet!mcvax!unido!fauern!faui44!mlelstv
From: mlelstv@faui44.informatik.uni-erlangen.de (Michael van Elst )
Newsgroups: comp.sys.amiga.tech
Subject: Re: Do all 3.5 inch drives use the same encoding
Message-ID: <739@faui10.informatik.uni-erlangen.de>
Date: 17 Nov 88 14:08:06 GMT
References: <8811101847.AA22940@godzilla.eecg.toronto.edu> <5231@cbmvax.UUCP>
Reply-To: mlelstv@faui44.UUCP (Michael van Elst (kdebugger))
Organization: CSD., University of Erlangen, W - Germany
Lines: 40

In article <5231@cbmvax.UUCP> daveh@cbmvax.UUCP (Dave Haynie) writes:
>in article <8811101847.AA22940@godzilla.eecg.toronto.edu>, leblanc@eecg.toronto.edu (Marcel LeBlanc) says:
>> Summary: 3.5 inch sector encoding question
>> 
>> []
>> 	Can somebody tell me if Amigas, IBMs, 1581s (CBM 8-bit), and Ataris
>> use a compatible encoding method for 3.5" disk sectors?  
>
>...  Any IBM based system with a floppy controller
>chip than can read and write full raw tracks could read and write Amiga
>disks with the appropriate program, but I suspect most controllers can't
>do this.
>

A friend who uses an CP/M computer has tried to read Amiga disks
with his WD1797 controller. We've got results. But there are some
problems with the Amiga format.

First, the controller cannot write full tracks because some
data bytes are interpreted as format control codes to generate
CRCs, SYNC bytes, etc. So writing Amiga disks will be impossible.
(Say nearly, you could encode your data to ensure that the complete
track information does not contain any of these control codes, but
its easier to read other formats with the Amiga controller).

Second, reading is done well with a read track command.
You get the encoded data and have to split the odd/even bits but
you can reconstruct the data sectors.
EXCEPT for data that is placed at the index hole of the disk !!
The controller starts/stops the read track command when an
index pulse is detected.
Thus you have to mask this signal and feed a timer based signal
into the controller chip.
Then you get all sectors.

If someone is interested. Please E-mail.

				Michael van Elst

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