Seiko Epson RTC-65271 Real Time Clock Datasheet

RTC-65271 Module
RTC-65271 Module

I have a stash of RTC65271 real-time clock modules and might use one in an upcoming project. They’re obsolete by nigh onto two decades, but it’s a one-off project and I know I’ve been saving these things for some good reason.

Alas, the datasheet doesn’t seem to appear anywhere else on the web; you can find an overview & general description, but not how the thing actually works.

However, if you happen to have a chip and need the datasheet, this is indeed your lucky day: a scanned RTC65271 Datasheet.

The datasheet alleges it’s “functionally compatible with MC146818A and DS1287“, and those datasheets may be more readable, if not exactly applicable. It seems to be (similar to) the clock chip used in the original PC/AT, if you recall those relics, and might actually use standard hardware & software protocols.

Dealing with this thing may be more trouble than it’s worth in this day of bus-less microcontrollers with Serial Peripheral Interface widgetry. A back-of-the-envelope count says it’d require three ‘595 output chips and a ‘166 input chip to fit on an SPI bus. Yuch…

Hey, if you want one, drop me a note. I have far more than a lifetime supply at my current rate of consumption.