The hardware
solution is to disconnect the internal serial cable from the
termianl logic PCB (the rearmost vertical PCB in the machine) and replace
it with one of the cables that goes to a DB25 connector on the back
(these cables are normally connected to the serial port PCB plugged into
the computer mainboard, just in front of the terminal logic PCB). The
cables have a Molex 0.1" pitch SIL connector on the end, and fortunately,
the pinout of all the internal serial connectors (terminal logic PCB,
computer 'console port', serial port PCB) is the same.
Ouch...
The software solution is to write a little
program that transfers
characters between the computer's console port and one of the other
serial ports. This will then make the computer section appear as a
transparent link between the terminal and the outside world.
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
This is obviously some new definition of 'much easier' :-)...
You're suggesting I find some program I've never heard of (OK, google
will presumably find it) and then transfer it onto an H89 disk -- some
H89s have hard-sector controllers only, so transfering it could be
'interesting'... What if the only OS you have for your H89 is HDOS? (I
assume this is a CP/M program).
I'm suggesting opening the case (2 spring catches) and swapping round 2
internal cables. No rewiring, no soldering, etc. Admittedly the terminal
logic board is a _pain_ to get to, but....
I guess if you just want to use the H89 as a terminal, then the hardware
solution is easier (you also don't have to boot CP/M and run a program).
If you want ot be able to switch between using it as a computer and using
it as a terminal then you need to track down this program.
H8/89. Plug your device into the spare serial port on
the back of the
(unopened) machine, and that should do it. Some '89's have three-port
serial cards... I don't know which ends up being which or whether MDM712
I think the 3-port card (3 off 8250) is standard... Now there's a thought
-- putting 16550s in an H89 and modifying the software to use the FIFOs...
lets you choose, all of my '89's are down
right now. :-/
What's wrong with them? These machines are not exactly complicated or
hard to fix (at least not compared with some machines I've worked on).
-tony