On 2015-Dec-15, at 6:21 PM, Mike Ross wrote:
> On Wed, Dec 16, 2015 at 11:43 AM, Mike Stein <mhs.st...@gmail.com> wrote:
>
> I have taken Brent up on that :-)
>
> I'll poke a bit more myself and see what we can work out together
> before I decide if the effort is worth it.
First crack can be picked up here:
http://www.cs.ubc.ca/~hilpert/tmp/WIOSelectric.pdf
There are a few areas and pins I couldn't discern from the photos.
Mostly around U1 & U6 as the lens angle and lighting is hiding some connections
around those.
If you take another photo or check some of the connections marked in red I can
update the schematic.
I've labeled the host interface connections as per the most likely scenario:
D0-D6: in correspondence to the 'normal' PROM addressing, so D0 is
likely the ASCII LSB.
nSTB: this should be the print-strobe input, looks like active-low.
BUSY/RDY: haven't examined the logic enough to say whether this
active-high or -low for whichever way one chooses to interpret it - BUSY /
READY / ACK.
So there are 10 sigs out of the proms heading off to the selectric mechanism
for the tilt/rotate / operation select.
But there are a lot of other connections to the mechanism. I've never played
with Selectrics internally so I'm not familiar with the details of operation,
sequencing, etc.
Note that only half the prom address space is accessed from the 7-bit data, and
it looks like the board is set up so if a trace is cut and/or a switch added
one could have two character code-sets. Who knows whether the PROMS are
programmed for such though.
I threw out a print-only selectric a few years ago that had been used for
printing airline tickets. No electronics in it, just the solenoids and contacts
for the electrical control. Regret it now, just because it would have been fun
to figure it out. C'est la vie.
