Mystery IC: Allen Bradley 314B102

Mike Ross tmfdmike at
Mon Dec 14 19:54:08 CST 2015

On Tue, Dec 15, 2015 at 1:21 PM, Fred Cisin <cisin at> wrote:
> On Tue, 15 Dec 2015, Mike Ross wrote:

>> That was my conclusion too. The old Western I/O ads I've seen
>> definitely refer to it as having an 'ASCII' or 'parallel' interface.
>> Assuming they only ever made the two models; I suppose it *could* be
>> some variant of RS232, with very non-standard pinouts - but the ads
>> are specific; they made a smart terminal with 6800 CPU & serial
>> interface, and a dumb printer with an 'ASCII parallel' interface. And
>> that's all I have to go on, beyond prodding the hardware.
> REMEMBER, "ASCII parallel" does NOT necessarily mean "centronics-style", as
> was used on TRS80, IBM PC, etc.  "Centronics-style"  was a good system, but
> it was NOT the only one.
> "ASCII parallel" could just as easily mean SEVEN bit, with a bit or two in
> each direction for handshaking.   "ASCII" was SEVEN bits, not EIGHT.

I guessed that might be the case... any suggestions for what were
common pinouts and signals used? I can analyze 'backwards', testing
possible suggestions, as fast or faster than I can do it 'forwards',
trying to recreate a schematic from examination of the hardware. It
sounds a lot like what we have here. But I'm not certain a modern
standard parallel port can ever be trivially adapted to drive this

> There was a time, 35 years ago, when "standard parallel" was an oxymoron.
>> leads, 7 lines... I'd expect to see 8 data lines all going to the same
>> place if it was anything resembling standard Centronics but with a
>> weird pinout. So I'm scratching my head still over just exactly what
>> it was supposed to hook up to.
> something other than "Centronics"?

I thought Centronics dated back to early 1970s - not always in the
standard 'modern' form, but in general principles with same signaling
and strobing of data.

Thanks for input!

'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.'

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