On Fri, Jun 7, 2019 at 6:50 PM CuriousMarc <[email protected]> wrote: > > >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. >
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
