On Sunday (02/08/2009 at 05:10PM -0600), Chris Elmquist wrote:
Now I'm working on figuring out the serial and parallel interfaces.
The brains are an 8048 microcontroller and then it looks like the serial
interface is handled by a classic old AY-3-1015 UART, which I'm assuming
front-ends the parallel interface. Lots more discovery there...
Just to close out this saga, I got lucky and after only a few trial and
errors, discovered that the unit accepts 300 baud, 8 bit, no parity,
I think I;d have reduced the number of trial-and-errors by (a) looking at
the state of the (5) model-select pins on that UART chip. They define the
word size, parity and number of stop bits. And then I'd have hung a
counter off the Rx clock pin of the UART (pin 17 IIRC) and measured the
frequency. It's 16 times tbe baud rate.
1 stop on a female DB25 DTE connection. It needs DSR
on pin 6 asserted
before it will respond.
But then whatever I send down the wire with those parameters, gets
punched on the tape. It works! It's very fast and very quiet compared
to an ASR-33 :-)
My guess is that it'll keep up with the 300 baud data stream (i.e. 30
cps) and not need any flow control lines. That was quite common in paper
tape punches -- the maximum available baud rate corresponted to the speed
of the mechanism (or a litttle less).
This was a nice save.
Still searching for a manual though, because there are switches in there
that I don't know what they do... and you know, a guy could loose sleep
It can't be that complicated... Noe's the time to learn the gentle art of
tracing out a schematic...