Async logic

Ethan Dicks ethan.dicks at gmail.com
Wed Mar 24 14:41:50 CDT 2010


On Wed, Mar 24, 2010 at 3:01 PM, Dave McGuire <mcguire at neurotica.com> wrote:
> On Mar 22, 2010, at 5:07 PM, Brent Hilpert wrote:
>>
>> I dealt with a reasonably complex async-design logic system from the 60's
>> in
>> reverse-engineering and repairing a Casio AL-1000 calculator:
>>   http://www.cs.ubc.ca/~hilpert/eec/misc/CasioAL1000Tech/index.html
>> and in particular:
>>
>> http://www.cs.ubc.ca/~hilpert/eec/misc/CasioAL1000Tech/electronics.html#edgepulse
>> What I call 'edge-pulse gates' - a sort of monostable - are injected into
>> the
>> logic at appropriate places to soak up the glitches (one would have to
>> look at
>> the schematic to see where/how they are actually used).
>
>  Wow.
>
>  I am impressed.  That's one of the most detailed and well-presented
> reverse-engineering projects I've ever seen.

Wow indeed!

That display looks familiar - I might have one on my shelf.  I picked
up a PCB loaded with vertically-mounted Nixies plus a neon-bulb
"minus" indicator many, many years ago at Dayton.  I have yet to
assemble a driver for it, but I've always thought about repurposing it
as a clock/calendar display.

The PCB has a small bundle of wires coming off one end, and the foil
pattern shows a multiplexed arrangement, IIRC (so 10 cathodes and
13-14 anodes, if I'm remembering it correctly).

I should check the PCB for any tell-tale markings.

Thanks for the link - it's certainly an interesting device.

-ethan



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