Path: utzoo!utgpu!jarvis.csri.toronto.edu!rutgers!mephisto!gatech!kd4nc!rbdc!barry
From: barry@rbdc (Barry Newberry)
Newsgroups: comp.sys.apple
Subject: Using Hardware to Control Serial Ports
Summary: It's almost enough to drive you nuts.
Message-ID: <1990Feb24.031856.26733@rbdc>
Date: 24 Feb 90 03:18:56 GMT
Reply-To: barry@rbdc.UUCP (Barry Newberry)
Distribution: usa
Organization: N.C. Home for Deranged Programmers
Lines: 48


Warning : there is a high probability of maniacs in engineering dept.

AAAAAIIIIGHHGHH !!!! (now that I have that out of my system ...)

This is dedicated to those of you who had such a nasty time trying to
use the IIgs serial ports via Hardware Addresses.

Lately, I have spent time disassembling ProTERM and analyzing the
code, because it is the best terminal program for the Apple II series
(in my opinion). Serial I/O seems to be done with the hardware addresses,
as opposed to the Pascal 1.1 protocol. The Super Serial Card is controlled
by normal hardware I/O addressing (r/w $C08n,X where X=slotx16). However,
the IIgs Serial Port is controlled by addresses $C038-C03B. These addresses
DIRECTLY read and write to the SCC 8530 command and data registers. The
standard rule for developers is "don't play with the registers." This
wouldn't be so bad if there was a map for the standard hardware addresses.
The SCC registers should only be used, when all (or at least most) commands
and settings for the SCC are understood. This causes trouble when some
things can only be done via the registers.

Is this madness or genius ?

The IIgs serial ports can be completely controlled via the SCC registers.
(At least that's what I have been led to believe.) This means that the
hardware addresses which are normally used for controlling a given slot
are not needed for controlling the serial ports. This, in turn, leaves
the serial port slots free for use by other cards, just select "Your Card"
for the slot in the Control Panel. Remember when people were talking about
being able to use slot 2 as a serial port and something else ? (possible
genius, hmmm... )

On the bad side, the hardware addresses $C000-C07F are getting real
crowded (in my opinion). There aren't many bytes left for additional
softswitches. Then again, you could use a byte (softswitch) to chose
between "old" IIgs I/O or "enhanced" IIgs I/O . ( <insert sarcasm>
"so, a LDA $C000 ... was that from the Main or the Alternate page ?")

So, does anyone have the hardware address map for the Super Serial
Card ? I know that $C084-C087, and $C08A have functions :-)  !
Also, who do I write for info on the SCC 8530 registers ?

P.S. : Thanks, J. B.
-- 
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