26 Jul
2006
26 Jul
'06
12:39 p.m.
Looking for thoughts on which machines used parallel
ASCII keyboards...
Many (perhaps most) older equipment with an integrated keyboard (ie: not
on a cable) used parallel keyboards - also any with an external keyboard on
a ribbon cable are likely parallel.
I've got a couple of working machines here that
used such a keyboard based
around the AY-3-4592 chip, but only one keyboard to go between them.
The interface between the keyboard and system is just 8 data lines and a
strobe though, all at TTL, so presumably any old keyboard that outputs ASCII
data could be made to work.
Ideally I'd like to find a real basket-case of a system that could provide me
with a donor keyboard. I'm not 100% happy with that, but providing the rest
doesn't go in the bin (such that it might be useful to someone at a later
date) and it's not something that's ultra-rare, it seems a reasonable thing to
do in order to complete an otherwise-pristine system.
Knowing which systems to look out for would be a start. Nascom, maybe? I think
RML 380Z's are probably parallel ASCII too, but their keyboards are already
rare as hen's teeth so I wouldn't be happy with that...
It would be dead simple to make an adapter to convert a standard PC serial keyboard
into an ASCII/strobe parallel interface - you get the added benefits of having lots of
extra keys, and the ability to assign whatever codes you like to them.
You could do it all easily with a single 8051 microcontroller - or if you can't
program
those, an 8031 (8051 with external ROM) would work equally nicely.
Somewhere around here I've got 8051 source code to a little project I did to convert
a PC keyboard to an RS-232 serial interface - It would be very little work to turn that
into a parallel interface.
Regards,
Dave
--
dave06a (at) Dave Dunfield
dunfield (dot) Firmware development services & tools: www.dunfield.com
com Collector of vintage computing equipment:
http://www.classiccmp.org/dunfield/index.html