5 Sep
2001
5 Sep
'01
2:56 p.m.
It's likely the patent will reveal whatever characteristics you're looking to
find. The modulation scheme is the only really valid claim that there is in
that patent, though the integration of some of the controller logic onto the
drive itself, and vice versa, is an innovation in the level of integration of
FDD drive/controller interfaces of the time.
Dick
----- Original Message -----
From: "Sean Gugler" <gugler(a)agames.com>
To: <classiccmp(a)classiccmp.org>
Sent: Wednesday, September 05, 2001 8:01 PM
Subject: Re: Apple ][ disk controller state machine
Tony, thanks for checking on this!
"Beneath Apple ProDOS" is probably what I want, then. I've never seen
either book, but I heard the second offered some recap and some fresh
material that was also useful to DOS 3.3 -- possibly the state machine
flowchart was among the fresh material, not recap.
Cheers,
- Sean
--
Sean Gugler ("Dr. Guz") guz(a)doctor.com
"This quote's just six words long."
Tony Duell wrote:
Until I get my hands on a copy of the venerable "Beneath Apple Dos"
is there anyone who can point me to an online resource describing the
Apple ][ disk controller P6 ROM state machine? The exact uses
for the Q6 and Q7 switches ($C0EC-$C0EF)? Or would be willing to
summarize from the mighty tome for me?
I've just pulled out my copy of 'Beneath Apple DOS', and the information
you need doesn't seem to be in there. There's very little about the disk
hardware at all -- it assumes you'll at least use the standard routines
to read/write bytes on the disk.
From the schematics in the Apple DOS manual, it
appears that Q7 is
inverted and turned into the write gate/ line to the disk drive.
So
presumanly Q7 is a write enable input (it does also go to the state
machine PROM and I guess it sets up the state machine for writing).
Q6 only goes to the state machine, so I have no idea what it's for (I've
not analysed the state machine -- yet!)
-tony