1 Oct
2015
1 Oct
'15
5:54 a.m.
I have been doing a bit of spadework on this one.
There was a company call MCT who advertised in the PC Mag. in the early
80's
The products were add-ons for PC's.
The possibiliy that they made S100 products prior to 1980 is not an
unreasonable one.
So anybody with an early 80's PC Mag might find them. In fact any
publication from about
then may have a reference.
Rod
On 01/10/2015 13:30, tony duell wrote:
Does 'now
days' include RS232 interfaces :-)
But before the 1488 (or at least before it was common), many manufacturers
used op-amps as RS232 drivers. Look at the HP11205 and 11206 interfaces
for the HP9830, for example.
For input I could believe taking the signal through a resistor to a zener diode
to ground. Remember a zener is reverse-biased in 'breakdown' mode so
that circuit will clamp +ve voltages to the zener voltages and -ve voltages (where
the zener is not the normal way round and therefore acts as a normal silicon
diode) to -0.6V. Or indeed resistor +diode clamps to +5V and ground. Then into
a TTL gate.
Given that the original connection was 3 wires, it's a good bet they were TxD, RxD
and
ground. Ground should be trivial to find. The trace the SO output of the UART to an
op-amp and then to the header. Similarly trace SI back through a TTL gate (which has
been mentioned already) to a header pin. I can't believe this is a complicated
circuit....
OK, I've been doing this sort of thing for years, but I wouldn't be surprised if
I could trace those connections in less time that it's taken to try to look for the
docs...
-tony
--
Wanted : KDJ11-E M8981 KK8-E M8300 KK8-E M8310 KK8-E M8320 KK8-E M8330
I'm fairly certain this is a serial board - mostly
because the PO told
me so, and when I received it, it had a 25-pin male connector on a
three-wire cable carelessly soldered to the pads behind one of the
cable headers on the top edge. But the cable was removed as a matter
of course when I was prepping the machine for a rebuild. I mistakenly
assumed that the docs would be trivial to locate - so no need to
record the original wiring connections.
no disputing that. Glad Tony made his point, I was curious if it was
early enough to not have had what we are accustomed to now days.