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From: urlichs@smurf.sub.org (Matthias Urlichs)
Newsgroups: comp.sys.mac.programmer
Subject: Re: Anyone have any SCC reprogramming hints?
Keywords: SCC program
Message-ID: <&u3mg2.it4@smurf.sub.org>
Date: 28 Nov 90 09:24:55 GMT
References: <30417.27493A91@stjhmc.fidonet.org> <804@macuni.mqcc.mq.oz>
Organization: University of Karlsruhe, FRG
Lines: 38

In comp.sys.mac.comm, article <804@macuni.mqcc.mq.oz>,
  s8925188@mqcomp.mq.oz (Philip Craig) writes:
< 
< Chris has reprogrammed the SCC completely, he says above.
< 
< My questions are related to this: Has anyone else done this, and how hard or
< easy was it to do? I am interested in running the SCC in a synchronous mode
< and using it's HDLC capabilities. Has anyone done this? Can you show me some
< source code :-) ?
< 
Yes, I did that a couple of years ago.
My project was to implement X.25 using the SCC chip instead of a Nubus card.
That project died because Apple Germany seemed to be unable to part with the
specs of Apple's X.25 driver interface (programs written for one should run
on the other, after all).

Source code? ahem... if you want to dig through my low-level stuff, with
variable names and (few) comments in German, be my guest. :-(

A better idea would be to get the Z8530 product specs from Zilog; the
document number printed on this booklet is 00-2439-01 and the phone number is
(408)370-8000. Implementation was, as I recall, work, but not impossible.
Especially since you can use the internal clock to set the 8530's speed to
one baud or so, and watch the data in real time -- serial analyzers are
expensive.

< I am also wondering: is the complete SCC functionality still there in the later
< models with all the VLSI chips? I mean, the Z8530 chip seems to have gone the
< way of the dodo in my IIfx, is it completely emulated by Apple's replacement,
< or is only the functionality that Apple uses ported across?
It's still there, only hidden. You would have to turn on the Compatibility
Mode (there's a CDEV for this), which tells the IOProcessor to hide itself
and mimi the Z8530 at some address or other. (There are low memory globals
for this.)

-- 
Matthias Urlichs -- urlichs@smurf.sub.org -- urlichs@smurf.ira.uka.de     /(o\
Humboldtstrasse 7 - 7500 Karlsruhe 1 - FRG -- +49+721+621127(0700-2330)   \o)/