11 Feb
2009
11 Feb
'09
11:53 a.m.
On Sunday (02/08/2009 at 05:10PM -0600), Chris Elmquist wrote:
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.
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, 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
over that.
It can't be that complicated... Noe's the time to learn the gentle art of
tracing out a schematic...
-tony