[Coco] deluxe rs-232 program pak

[gene heskett]

On Friday, December 30, 2011 08:03:43 PM Robert Hermanek did opine:

> I have an rs-232 cart here, and the screw has never been taken out, so I
> don't really want to break the nice label for this question:  anyone
> know if this cart has a socketed ROM in it that could be removed and
> replaced with custom eprom?
> 
Yes it does, but why?  It contains a program similar to teletext, a 35 year 
old protocol that was obsolete by the time the shack burnt the roms.  Most 
disconnect the roms CE line, or completely remove it. While I am not 
familiar with any of them, there are rsdos programs that use it, like the 
BBS stuff, and all the 'terminal' programs we used to access the likes of 
delphi/bix & princetons old now shut down server back when a 1200 baud 
modem was so fast it left a trail of smoke.  :)

We also have several os9 based term programs that can use it. The vt220 
emulation I have on my site (down in the sig), and supercom (beta 2.3) 
(it's there too) come to mind.

In the current nitros9 distribution, the drivers with sc6551 in their name 
will need to be added to your os9boot file by editing the files in 
BOOTLISTS.  Except for joydrv_6551l.sb, that is my 3 button mouse driver 
using a 2nd set of chips piggy backed on the originals in that pack.  That 
can also be used for a 2nd serial port at /t3 if you don't have/need the 
mouse.

Bear in mind also that this sc6551 chip is a bit dane bramaged at how it 
handles hardware flow control, and that there is a file kicking around that 
describes a logic fix for that, which requires basic soldering skills to 
do, plus if using an MPI, one needs to tie all 4 sockets together at pin 8 
and remove 3 of the 4 pullup resistors along the front edge of that pcb 
that are connected to those pin 8's.  This bypasses the slot selection 
logic in the MPI which causes IRQ blocking so an incoming byte gets 
serviced in good time instead of being thrown away because it wasn't 
grabbed in time.

Then it will run flawlessly at baud=6, or 9600 baud.  There are some 
additional tricks I don't have memorized that can make it work at 19,200 
baud too.

One other thing about those 232 packs today is that the teeny little tin 
canned aztec power converters in them are beginning to suffer from dried 
electrolytic caps.  I smoked mine (literally, made a nice stink) 15 years 
ago, pulled it out and ran 2 new traces to the card edge connector so it 
runs on the MPI's + and - 12 volts.

That pack wasn't very good, but until Mark designs a new one with modern 
chips in it, it is about the best we have, it just needs some fixing here 
and there.  :)

Welcome to the list Herman, and I hope this helps.

Cheers, Gene
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