H89 as serial terminal

From: Jason J. Gullickson <mr_at_jasongullickson.com>
Date: Mon Mar 31 10:19:00 2003

Hey guys, thanks for all the info.

I would prefer to go the software route (I'd prefer to run CPM and find
a C compiler...) but I'm having a hell of a time tracking down disks for
this thing so in the meantime I'm looking for a hardware hack to make it
useful (or at least make it do something to freak out my fellow
employees as my syslogs scroll across the screen of this beast), so the
hardware solution is what I was looking for (I could have been more
specific).

On that note, if any of you know where I could find a copy of CPM and a
compatible C compiler on hard-sectored disks, that would be greeeaaat,
yeah.

Thanks again!



-----Original Message-----
From: cctech-admin_at_classiccmp.org [mailto:cctech-admin_at_classiccmp.org]
On Behalf Of Patrick Rigney
Sent: Friday, March 28, 2003 1:02 AM
To: cctalk_at_classiccmp.org
Subject: RE: H89 as serial terminal


> >much easier than any of the above... get a copy of MDM712 or similar
> >terminal emulation program. MDM712 comes with a serial port driver
> >for
>
> Hi
> Why would you assume that finding and installing some software would
> be easier than making up a simple molex adapter connector. As I
> recall, it was a 9 pin molex but I could be wrong. That is all of 9
> wires to deal with. Dwight
>

Dwight, you're absolutly right, the software is not always "easy" to
find and get. Actually, check that... it's really easy to find and get
(Google), it's just not as easy to get onto a Heath-format floppy so you
can use it.

On the other hand, I think the software approach has its merits,
especially over the long haul. Using a terminal emulator is a more
permanent solution
(IMHO) than cracking the case and swapping connectors around to
reconfigure the device as a terminal or computer. And, the terminal
logic board communicates with the CPU board at 9600 baud, so if you want
a different rate for the device you are talking to, the board has to be
pulled and jumpers/switches changed, and then pulled and changed back if
you want to use it as a computer again. The three-port serial card has
software configurable baud rates. The hardware approach will also not
make it emulate VT-100, which is part of what Jason had asked. And
since many of these programs can X/Y/Zmodem, getting other stuff onto
the machine from there forward gets a lot simpler.

While you, I, and others may feel quite comfortable mucking around with
the innards of the beast, perhaps (and I don't know one way or another
for sure) Jason or anyone else who might later read this thread in
archives or digests may be less comfortable or is just working up to it,
and so other alternatives are worth mentioning (IMHO). Tony's hardware
solution is good, but rerouting even one of those cables may require
removal of the CPU and terminal logic boards, since the interconnect and
serial cables are typically routed around the bottom edge of the two
boards and fairly tight once home. If you're going to go back and forth
between terminal and computer, maybe that's a bit much in the long run.
Add to this that the expansion boards and some of the other connectors
attached the CPU board are all unkeyed and thus notoriously easy to
(re)install one pin off their mating connectors, and this little
accident can cause the kind of rapid deep frying on the CPU board that
will turn a wonderful H89 into a dumb terminal permanently.

I'm into risk management and choices. That's all. I certainly didn't
intend any offense with my comment.

But since we're into options... to elaborate on your and Tony's path,
the terminal logic board's serial port is easily accessed from the rear
of the machine--remove the lid, and as you face the back of the machine,
it's on your left (you can sometimes read "P404" next to it). If a
cable is the solution of choice, then Molex directly to a DB-9 or DB-25
(whatever the device to be connected requires) is the way to go, IMHO.
That way, you can just open the case, pull the interconnect, connect in
its place this new cable to the target device, and do your thing.
Reverse to undo, lather-rinse-repeat as needed. That won't get you
VT-100, software transfer, or other baud rates, but it is quick and
dirty.

To that end, P404 on the terminal logic board is a 15-pin connector with
10 pins connected. For those interested, the pinouts are (from
schematic w/no revision number evident, identified Heath p/n
595-2268/595-2272):

1 - (black) ground
2 - no connection
3 - (brown) TxD
4 - n/c
5 - (red) RxD
6 - n/c
7 - (orange) RTS
8 - n/c
9 - (yellow) CTS
10 - n/c
11 - (green) DSR
12 - n/c
13 - (blue) ground
14 - (violet) DTR
15 - (grey) "RLSD/" (whazzat? anybody?)

The black wire (pin 1) is up in this vertical connector.

Patrick
Received on Mon Mar 31 2003 - 10:19:00 BST