15 Dec
2015
15 Dec
'15
7:19 a.m.
Well, 19 could be a general printer-ready pin in
that if the paper runs
out it would say the printer is not ready for another character but
it might well also be put to the not-ready state when the printer
was printing the current character. Seen that before.
Maybe, but Selectrics aren't exactly fast devices; there's a whole lot
of potential 'no, wait, I'm not ready!' conditions. Would they all be
ORed onto one pin? I've gone over the connector again and we have ten
signal pins plus a
ground plane... that's *just* enough for 8 data bits, a strobe, a
ready/wait line... but that Allen Bradley pull-up pack is only 14
Why 8 data bits? ASCII (which we are assuming this is) is a 7 bit code.
A number of older printers did indeed only have 7 parallel data lines.
This board
does not look that complicated and all the ICs have known
numbers on them (mostly TTL logic). If it were mine I'd trace out the schematic.
That's true and possible. I'm in two minds on this thing: - intention was to rip all this out and convert it to
a full I/O
serial terminal, using an Arduino-based setup that Lawrence Wilkinson
has already built and tested:
In some ways I agree with doing that (other than using a a million more
components than you need...). On the other hand this board is part of the
history of the unit, so I would keep that if at all possible I think.
-tony