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From: mat6013@DMZRZU71.BITNET
Newsgroups: comp.sys.apple
Subject: Re: ProDOS patch (...)
Message-ID: <8708241100.aa03291@SMOKE.BRL.ARPA>
Date: Tue, 25-Aug-87 07:22:24 EDT
Article-I.D.: SMOKE.8708241100.aa03291
Posted: Tue Aug 25 07:22:24 1987
Date-Received: Wed, 26-Aug-87 05:43:09 EDT
Sender: daemon@ucbvax.BERKELEY.EDU
Organization: The ARPA Internet
Lines: 11

This  weekend  I  took  a  detailed  look at the ProDOS patcher program posted
5/8/87  to find out the changes applied to the "PRODOS" system file (I'm using
version  1.2).  Adding the "LDA $C08C,X" makes sense to me, but *why* was "STA
$C08n,X" changed to "LDA $C08n,X" (n= 0, 2, 4, 6) ?  These are for turning off
the  four  windings  of  the  stepper  motor which is responsible for the head
seeking.  So what's the difference between a read and a write operation here ?
The best documentation I have about the softswitches of the disk ][ controller
is "Beneath Apple DOS"; it tells nothing about that.

                                        Matthias Kapffer
                                        <MAT6013@DMZRZU71.BITNET>