H89 as serial terminal

From: Tony Duell <ard_at_p850ug1.demon.co.uk>
Date: Fri Mar 28 19:44:00 2003

> > 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
Received on Fri Mar 28 2003 - 19:44:00 GMT