Mystery IC: Allen Bradley 314B102

Mike Ross tmfdmike at
Mon Dec 14 03:52:33 CST 2015


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:

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:

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??

'No greater love hath a man than he lay down his life for his brother.
Not for millions, not for glory, not for fame.
For one person, in the dark, where no one will ever know or see.'

More information about the cctech mailing list