7 Jun
2019
7 Jun
'19
10:56 a.m.
On Fri, Jun 7, 2019 at 6:50 PM CuriousMarc <curiousmarc3 at gmail.com> wrote:
I wondered if it's actually a digtal watch chip (2.5V could have been a couple
of mercury cells in series, LED watches were not uncommon back then).
In which case it would not normally have come in a 0.6" wide DIP. Perhaps
normally it was a bare chip directly mounted on the watch circuit board or
something.
The DIP version would be unusual, which is perhaps why we can't find data
on it.
-tony
The clock chip seems to be a normal digital
watch/clock chip. The inputs to
it are essentially the 'set' buttons, the outputs are the 7 segment lines and
digit strobes. But I have not found a data sheet on it anywhere.
Tony, looks like
you are absolutely right, this would be a garden variety digital clock chip! Looking at
the schematics, U15:
https://drive.google.com/open?id=1kNq0-IUBcPKDAE8k4Ztg2eoUCWHPr4hI
The outputs Sa-Sg are standard names for 7-segments, and are read on the processor bus.
They don't bother to read segment d, I suppose they can differentiate all the numbers
without reading that one. DI must be the Decimal Indicate segment. D1-D3 would be the
digit counter. C25, READ and SET are the inputs - we'd have to find what they exactly
do. Would they then set the clock by just toggling the digits in one by one as one would
do to reset a clock? Anyhow, it seems I could set the Sa-Sg signal to test pattern and see
if indeed I read digits different than 8, and confirm that everything is working but the
clock chip. Now, how to find a more or less equivalent replacement chip.