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From: frankjr@Neon.Stanford.EDU (Frank AnthonyJr Busalacchi)
Newsgroups: comp.sys.amiga.hardware
Subject: Re: Decoding MFM
Message-ID: <1991Feb12.075454.6227@Neon.Stanford.EDU>
Date: 12 Feb 91 07:54:54 GMT
References: <2786@gould.doc.ic.ac.uk> <1074@usage.csd.unsw.oz.au>
Organization: Computer Science Department, Stanford University
Lines: 34

s1013734@usage.csd.oz (Peter Urbanec,5SK,6621322,6621322) writes:

>From article <2786@gould.doc.ic.ac.uk>, by la@doc.ic.ac.uk (Liaket Ali):
>> 
>> Could anyone offer some help (info/source) on how to convert raw MFM data into
>> intelligible information. In the RKM Libs&Devs, mention is made of the use of
>> the blitter in this task but I could not find any further info on it. Also is
>> it possible to use the CPU to do the decoding.
>>

>Sure you can do encoding and decoding using the CPU, just write a program that
>will do exactly the kind bit of decode described in RKM (11->01 type of thing)
>Programing the blitter to do it is rather tricky, but I know that people have
>done it in the past. The Abacus book `Amiga DiskDrives inside and out' might have
>routines that do it, but I think they would be processor based.

>	BUT!!!!

>Why the hell would you want to do it by yourself? You can get the trackdisk device
>to give you your data in the proper form.

The routines are actually in the ROMS I think.  The abacus book on disk drives
#9 has the routines printed out and documented.  I suggest that you get ahold
of the book.  Really good book as all ABACUS books seem to be.

Abacus #6- Amiga System Programmer's Guide is an excellent book if you are
interested in how the custom chips do their work etc.  It basically teaches
you how to be a bad amiga programmer, and go straight to the chips to do
things like sprites bobs, blitter, scrolling reading joysticks mice etc.

Frank Busalacchi Jr
Stanford University Undergraduate Computer Science Department
Unix Consultant
Software Alchemy