[Gibbon1]

That's gold.

That hardware real time clocks keep time in date and time drives me batty. And no one does the right thing which is just a 64 bit counter counting 32khz ticks. Then use canned tested code to convert that to butt scratching monkey time.

Story my old boss designed an STD Bus RTC card in 1978 or something. Kept time in YY:MM:DD HH:MM:SS 1/60 sec. And was battery backed. With shadow registers that latched the time. Couple of years later redesigned it as a 32 bit seconds counter. With a 32khz sub seconds counter. Plus a 48 bit offset register. What was a whole card was now a couple of 4000 series IC's on the processor card. He wrote 400 bytes of Z80 assembly to convert that to date and time. He said was tricky to get right but once done was done.

[Someone]

I would guess that’s because those chips were designed for use in systems that didn’t have a CPU, but reading the data sheet, it doesn’t look as if you can easily hook up this thing to 7-segment LEDs, so maybe this is a matter of “this is how we always did it, and if it ain’t broke, don’t fix it”, and then ‘fix’ it, anyways?

[alsetmusic]

I had some interactions with the guy responsible for the code that made our system do the right thing around Daylight Saving. Listening to him talk out loud as he thought about bugs was fascinating. He was clearly one of the smartest people I've met and I would quickly fall behind as he rationalized problems to himself. What a marvelous mind.

[kevin_thibedeau]

Some of them do have an epoch counter in addition to broken down time.

[Gibbon1]

The Renesas RTC divides the 32khz clock by 256. And after waking up doesn't update the shadow registers till the next tick. So if you wake out of deep sleep you don't know what the time is for 8ms.

I know of one that draws 0.5uA in normal mode but 12uA in binary counter mode.

[ralferoo]

I propose naming the code that ensures this 8ms has elapsed "the yawn".

But to be fair, it doesn't seem that onerous an issue - the biggest problem would have been if this was completely undocumented. One obvious workaround is to read the time immediately on wake up, and then ignore the result until reading the time returns something different.