[Coco] POSSIBLE Solutions For RS-232 Problem
Joe Schutts
j_schutts at yahoo.com
Thu Feb 22 10:56:25 EST 2018
Hi Everyone,
I have been following the E-Mails about the problems everyone has been having with the RS-232 Pack and it's flaws (especially you Allen ((is it Huffman??)). Anyway Allen, this might be something that might help you, that is if you didn't already know about it. If you did than just disregard it. Hey, at least I tried...
I recently came across an article from someone (I don't know who) about a POSSIBLE FIX (OR PATCH) for the CoCo RS-232 Pack and I thought I'd share (the article) with everyone who's been trying to FIX this problem in that it might finally happen.
Anyway here it is, I hope this helps...
P.S. I apologize for the text format (of the article - It's 5 pages by the way), but this is how I got it...
Joe...
6551 Hardware Hack 14 April 1991 by Terry Trapp (CoCo Max)
6551 Hardware Hack By Terry Trapp
How many times have you said to yourself, "I wish
my 232 Pak would work correctly with my BBS." Dont you
just hate it when you can't see modem responses? :(
It's all because of the 6551 chip in your 232 pak or
Disto 4-in-1 board. It will not allow you to receive
any information from the modem when there is no "Carrier
detect", or "CD" for short. Bruce Isted saw this
problem and decided to write a driver called "SACIA". It
is a fully buffered driver that does one special thing
... it will allow you to swap "DSR" <Data Set Ready> and
"CD" on your cable. DSR is always on when you have a
modem hooked up. What you would do with this driver is
swap pin 6 <DSR> and pin 8 <CD> (An inverted cable) &
SACIA will look at the DSR location for carrier. CD
will always be on, so you can see modem responses.
That's fine and dandy with the 232 pak, but with the 4
in 1 board from Disto -- Now that's a little different.
:(
The 4 in 1
I got my 4 in 1 three days ago. I took my boot
disk over to Trix's house (John Farrar) and begged him
to install my device drivers for the SC II & the 4 in 1
board. (He's the software dude, I'm the hardware
dude--- together we make a good CoCo programmer. :) )
He installed my new drivers but left SACIA in place, he
just changed the loaction of where to find the 6551
chip. It should work right?? Eaaaa! Wrong answer
thanks for playing! Tony did something different to his
6551 than the one in the Deluxe RS-232 Pak. I fired up
RiBBS and BOOM! Carrier Detected! DARN! Ok, I'll
disconnect my modem, it will lose carrier then! Eaaaa,
Sorry wrong answer thanks for playing! It still had
carrier. Why is it doing this??? Look on page 5 of
your Disto 4-in-1 board manual. In the middle of the
page you see--
** The CTS (Clear To Send) and DSR (Data Set
Ready) input signals to the ACIA are always
enabled. This means the ACIA device will
always transmit, reguardless of what is
connected to it.
What Tony doesnt tell you is that the 6551 <The
ACIA device> will ALWAYS transmit regardless of DSR. I
sat down and thought to myself-- "I bet he just "Hard
Wired" DSR on!" <Hard Wired means physicaly wired> As I
came to find out after about 2 hours of trial and error
voltage readings, Pin 16 is at 0 volts when CD is on,
and at 5v when it is off. The same is true with Pin 17.
- Page 1 -
6551 Hardware Hack 14 April 1991 by Terry Trapp (CoCo Max)
When DSR is on, 0v is on Pin 17. When DSR is off, 5v is
present on Pin 17. <I found this out with my Deluxe
RS-232 Pak>.
pin | on | off | use
---------------------------------
16 | 0v | 5v | CD
17 | 0v | 5v | DSR
DSR, Pin 17 on the 4 in 1 is soldered to ground.
That means there is no voltage on that lead. Therefore
DSR is ALWAYS on. That is why I ALWAYS detected carrier
with the inverted cable and SACIA. The 4-n-1 CAN'T read
DSR from the modem, the hardware isn't connected from
the modem to the 4-n-1's 6551. The Deluxe RS-232 DOES
have the hardware, therefore an inverted cable can be
used with it.
BE CAREFUL MODIFING YOUR 4 n 1, SERIOUS DAMAGE CAN OCCUR
IF YOU ARE NOT CAREFUL. IF YOU HAVE _ANY_ PROBLEMS
UNDERSTANDING THE MOD.----
-=*DO-NOT-ATTEMPT-IT*=-
Get help from someone if you can, or leave me mail
on my bbs. Electronics work on blue smoke, if you
accidently let the smoke out----- they wont work! :)
- Page 2 -
6551 Hardware Hack 14 April 1991 by Terry Trapp (CoCo Max)
The Modification
Here is how to mod. the 4-in-1 for SACIA or any
other "Inverted Cable" driver.
1) Disconnect all power and connections from the Disto
SC II.
2) Unscrew the 4 screws that hold the cover on.
3) Remove the cover carefully.
4) Get a static wrist strap and put it on.
5) Place the wrist strap's ground to the SC II's CoCo
edge card ground located at either end of the CoCo
connector.
6) Carefully disconnect the 4-in-1 board.
7) Locate the 6551ap chip.
8) Locate Pins 16 & 17 on the 6551ap.
9) Flip the board to the BACK side.
10) Locate the trace going from Pin 16 to a Node on the
circuit board. <A Node looks like a little round
solder blotch, the trace continues on the top side
of the 4 in 1 board>
11) Cut the trace as close to pin 16 as possible with an
"Exacto knife". Be SURE the trace is CUT. Take a
continuity reading <if you can> to be sure.
12) Flip the board back over to the TOP side and cut Pin
17 off of the circuit board. CUT IT CLOSEST TO THE
BOARD -=*NOT*=- THE CHIP.
13) On Top of the board, solder a piece of solid wire
through the node that used to goto Pin 16.
14) Solder the other end of the wire to pin 17 of the
6551. NOT the pin on the board, the chip itself.
15) Flip the board over to the BACK side.
16) Solder another wire to Pin 16 of the 6551.
17) Solder the other end of the wire to ground. <I used
the larger trace located closest to the pin, GOING
UNDER the 6551 chip.>
18) Re-Install the modified 4 in 1. <Be careful to get
all the connectors back in their correct positions>
19) Disconnect the static strap.
- Page 3 -
6551 Hardware Hack 14 April 1991 by Terry Trapp (CoCo Max)
20) Place the cover back on the 4 in 1, be sure none of
the mod. you made will short to ground.
21) Connect everything back together.
22) Pray.
23) Turn on the CoCo, If you get an "OK" with a "Disco
Cursor" boot OS9 and see if it works!! If your
CoCo crashes when you cut it on, remove the cover
to the SC II and check all your connections.
- Page 4 -
6551 Hardware Hack 14 April 1991 by Terry Trapp (CoCo Max)
The Conclusion
And there you have it! Simple Huh?? CD is
always on, and DSR is connected to the CD from the
modem. SACIA will change it back to CD for you!!
No need to even set RiBBS up for an inverted
cable. No need for an inverted cable, it is all
done my the Mod. and SACIA!!!
I hope you have no trouble with this mod. If
you need any help, you can reach me at
(615)-781-8679 DATA 2400 8n1, or through Fidonet at
1:116/41. Also you can send mail to me via TRIX on
Delphi.
P.S. As of this date 01/04/91, I have had no
trouble with the mod.
Terry Trapp Copyright 1991 By Terry Trapp
"CoCo Max" This document is free.
SACIA is Copyrighted By Bruce Isted and comes with
The Eliminator Software Revision 1 Update
The Elimatior is Copyrighted By Frank Hogg Labs.
The DISTO SuperController II and 4-n-1 board are
Copyrighted by DISTO.
------------------
1 --| |____| |-- 28
2 --| |-- 27
3 --| |-- 26
4 --| |-- 25
5 --| |-- 24
6 --| 6551 ap |-- 23
7 --| |-- 22
8 --| |-- 21
9 --| |-- 20
10 --| |-- 19
11 --| |-- 18
12 --| |-- 17 <-DSR
13 --| |-- 16 <-CD
14 --| |-- 15
------------------
- Page 5 -
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