Help with IIGS Slot Register $C02D

[Hugh Hood <hughhood@earthlink.net>]

Fellas,

I'm stumped, so it's definitely time to phone a friend...

I regularly use three printers with my IIGS systems, and keep them all
connected to either the IIGS built-in serial ports or to parallel cards in
Slots 1 and 2. (e.g. Laserjet for most printing, NEC Spinwriter Impact for
2-part checks, Houston Instruments Plotter for engineering drawings).
Each has its own purpose.

Anyway, I'm working on a project for Classic AppleWorks (which when
perfected I believe will be pretty slick and worth sharing) that uses a
_4th_ device to be attached to the IIGS via one of the built-in serial ports
and will need the serial port firmware in order to be useful with
AppleWorks. The 4th device is a serial terminal connection to the Unix side
of a Mac, like that I described in the how-to article on Sean's
A2Central.com site.

To switch between devices attached to Slots 1 and 2, I modify the bits in
the Slot Register at $C02D. Using the UltraMacros dot commands .AndBits and
.xor you play with a couple of bits to choose between either the built-in
serial port or 'Your Card'. Of course, you need to keep track of which is
currently selected or you risk accessing the wrong device. Plus, if you
access the Control Panel or re-boot the default Control Panel settings are
restored.

Here's the problem --

Provided Slots 1 and 2 are set in the Control Panel to the built-in serial
ports (either Printer or Modem), I can change between the built-in serial
port and Your Card without problem. If, however, Slots 1 and/or 2 are set to
'Your Card' initially, I cannot successfully switch to the built-in port by
modifying the Slot Register at $C02D.

If I attempt to change from the default 'Your Card' to the built-in serial
port, output 'vanishes' and is sent to neither.

I've confirmed (by looking at $C100/$C200 etc) that the firmware does
change, but I just don't get output.

I've tried initializing the serial port firmware via the Pascal 1.1 entry,
but that doesn't seem to help.

I've tried using ProTerm to access the built-in serial port (since it
doesn't use the firmware) and reset the SCC. ProTerm accesses the serial
port without problem, but it doesn't solve my problem.

So ...

It seems that some 'piece' that is loaded when the built-in serial port is
selected as the Control Panel default is not in place when I make the switch
from 'Your Card' to the built-in port via the Slot Register method.

What is that piece, and how can I load it after-the-fact? Or is it something
else, say, pertaining to the SCC?

Thanks.



Hugh Hood

FWIW - For reasons not addressed here, I'd rather not have to set both slots
to built-in port in the Control Panel.