Mystery IC: Allen Bradley 314B102

tony duell ard at
Tue Dec 15 09:35:59 CST 2015

> I guessed that might be the case... any suggestions for what were
> common pinouts and signals used? I can analyze 'backwards', testing

There were just about as many parallel interface versions as devices
that used them back then..... Nothing 'common' really...

The idea of 7 or 8 data lines, a strobe, and a ready signal was 
certainly arround back then, but the timing, polarity (active high
or low) and timing were not standardised. A couple of examples
that I can see without getting up are the Facit 4070 paper
tape punch and the HP9866A thermal printer. Those were
both around in the early-mid 1970s and are rather different
parallel interface.

OK, what I would do to get some idea is focus on those 7475 chips. Get
the pinout. The most obvious use for them on this board is as the
character input latch. IIRC each is really 2 2-bit latches, so 2 enable/clock
pins on each chip. So : 

1) Are the 4 clock pins linked together (if so, it loads a character at a time [1]), 
or are they in pairs or what

2) Where do the D inputs go? Are any of them linked together, or do 7 or
8 of them go to the interface connector? If the latter, then those are the data

[1] Before anyone suggests you could use them as a sort-of shift register and load
half a character into one, then copy it into the second one while loading the other half
character, remember the 7475 is a transparent latch, not an edge-triggered flip-flop 
making this a very difficult thing to do.

If you can identify the data lines on the connector you are getting there. See if you 
can trace the other pins to inputs or outputs. 


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