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.

6 thoughts on “Seiko Epson RTC-65271 Real Time Clock Datasheet

  1. I would ask for one, but then I’d also have a lifetime supply…

    As it is I found some mc14495 chips – BCD to Seven Segment Hex Decoders – on an old board and decided to fire them up. Also obsolete by a few decades.

  2. And yup – I blogged about the 7-segment chips. ( I found a place on the net selling the 7-segment chips for $15. You might consider selling your chips. It could be your retirement fund… :-) I think that the chips must be in demand for replacement/service parts.

    Makes me consider going through all of my old tubes of chips. Perhaps I’m sitting on a gold mine.

    1. Perhaps I’m sitting on a gold mine.

      Now, there’s a thought… I knew I was saving those LSTTL chips for some good reason!

      1. If I could get $0.10 for each of my chips (and I really doubt I could) I would be able to make a mortgage payment. In my years of engineering I had a ton (not quite literally) of old chips dumped on me. There are probably some of high value to _somebody_ in there, but I’ll likely toss them before ever sorting through them. Too many, too little time.

        Once, ages ago, I used to pad orders of electrical components from catalog companies with assortments of TTL chips in order to get the order up to the $25 or $50 minimum order level. Now days I do something similar. Every Digikey on-line order gets padded with AVR microcontrollers.

  3. Thanks for posting this! I too have a few and couldn’t find the full datasheet anywhere.

    Thanks again.

    1. Glad to help!

      Now, you’ve got to actually use the things and shame me into action…

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