> > > 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?
Why not? It's all the host really needs to know -- can I send another character or not. [...] > 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: I reckon it would take me a couple of hours at most..... > - 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