Mystery 8085-related IC identification needed please

Tony Duell ard.p850ug1 at
Fri Dec 16 12:25:21 CST 2016

On Fri, Dec 16, 2016 at 6:19 PM, Peter Coghlan <cctalk at> wrote:
>> They aren't 'standard' 14-pin DIPs in that they don't follow the
>> GND-on-pin-7-Vcc-on-pin-14 layout. Pins 6 and 7 on both are wired together
>> (not to GND) and form the RESET signal for the 8085 via the 7414 at 10A,
>> source for this signal is unknown currently. Pin 5 on both appears to be Vcc
>> and pin 10 is GND or at least are pulled high and low respectively.
> Could they be 74(LS)90? Those have Vcc on pin 5 and GND on pin 10.

And IIRC pins 6 and 7 are reset _inputs_ on the 74x90 (I don't have the
pinouts to hand, what about the 74x92 or more likely 74x93?). But active
high, not active low. So it's possible the reset signal comes from elsewhere,
resets these counters (as some kind of clock divider chain) and is inverted
by that '14 to feed the 8085 reset input.

I doubt it's a uA733. I can think of no logical reason to have one of those
in this sort of circuit.


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