Mystery IC: Allen Bradley 314B102

[Mike Ross]

Folks,

I'm still probing the alleged "parallel ASCII" interface that was
supposedly fitted to my 'Western I/O' converted IBM 2970 Selectric.
Here's where we're at:

http://corestore.org/2970pins.jpg

I've traced the pins from the DB25 connector back to the board; the
ribbon cable in the above pic is straight-through to the DB25. It
doesn't resemble any interface with which I'm familiar, and I can't
see how it can possibly be parallel. Only the following pins (these
are the DB25 pin numbers remember) connect to any pins or devices on
the interface board: 9, 10, 11, 13, 17, 19, 21, 22, 23, 24.

All other pins are either unconnected, or ground.

Of the above 10 pins, 11, 13, 22 & 23 are high at power-up (printer
NOT connected to any interface). The only pin with known function is
19, which is 'paper out'; if I toggle the paper out switch I can see
it going high and low.

There is no frigging way that can be a conventional 8-bit parallel
interface, obviously, with only 10 pins in use, and 4 or 5 of them
(depending on paper out) high on power-up - obviously signaling
something. Whatever it is, most of the pins are driven by an IC - an
Allen Bradley 314B102. Google has nothing, except a few for sale. No
datasheet anywhere I can find.

Can anyone give me a clue as to the purpose and pinouts of an Allen
Bradley 314B102??!!

Here's the component side of the driver board, the interface and
314B102 bottom right:

http://corestore.org/2970driver.jpg

Help? Please? Anyone out there with old reference material? Anyone
make a stab at what the hell this interface might be??? Maybe, maybe,
it's some kind of custom 'internal' interface and was intended to be
used with a (missing) external converter box/cable that made a
standard parallel interface of it??

Mike

http://www.corestore.org
'No greater love hath a man than he lay down his life for his brother.
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For one person, in the dark, where no one will ever know or see.'