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Joe Horn · 12-07-2016, 06:42 AM

(12-06-2016 09:23 PM)DavidM Wrote:
(12-06-2016 07:43 PM)Joe Horn Wrote: This whole issue of the 50g turning itself on periodically was covered by Bill Wickes on page 622 of his book "HP 48 Insights, Part II". ...

Bottom line: Every HP 48/49/50 which is not awakened by something else will wake itself up every 3 days, 49 minutes, and 4 seconds, and then turn itself right back off. [Maybe the HP 28 too?]

Yes, that's the same thing I was referring to in a previous post about the timer (TIMER2, specifically) that expires and creates a "timer reset" interrupt when it happens.

However... I don't believe that's the power-up that is being referred to by others in this thread. Why? Because that particular power-up happens as an interrupt that performs its functions and shuts down without engaging the normal System Outer Loop. As such, it shouldn't normally set up a situation where the system is left powered on -- which would presumably be required in order to trigger the "auto power-off" that is happening for folks that have a STARTOFF program defined when these random power-ups occur.

But STARTOFF *is* executed every 262144 seconds (if no other interrupts occur in the meantime). The power-up that Wickes is talking about DOES engage the System Outer Loop, and it does turn on the display. If there is no STARTOFF program, and you happen to be looking at your 50g when the 262144 seconds have elapsed, you'll actually see the display blink on VERY briefly, and then turn off again. If STARTOFF exists, it'll be executed. None of this applies if ANY other interrupt occurs before the 262144 seconds have elapsed, in which case that timer gets reset to 262144 seconds again.

(12-06-2016 09:23 PM)DavidM Wrote: The 52-bit RAM register referred to by Wickes above is actually the date/time (in TICKS format) of the so-called "Next Event". I've seen references to that Next Event being any of several different things, including (but not necessarily limited to):

- The next second transition if powered on and the clock is displayed
- The next auto-poweroff if currently powered-on
- The next time an alarm is due
- The next time an "auto wake-up to reset TIMER2" occurs (if powered off)
- One hour after the last keypress was popped from the key buffer

Never heard of that last one. Interesting. Every keystroke also causes an interrupt which resets the timer. The blinking cursor is also controlled by a timer, but that has its own separate timer. In any case, when no other "next event" is scheduled, the "next event" is automatically set to 262144 seconds and the calculator turns off. That's what the second-to-last entry in your list above refers to. As Wickes said, this is necessary to keep the system date & time correct.

(12-06-2016 09:23 PM)DavidM Wrote: Although I'm fairly certain we'll never see a fix, perhaps we can eventually find a way to work around it (or at least predict it better) if we find out more about the source of the problem.

It's not a problem. It's a feature. And it's totally predictable: exactly every 262144 seconds, if no other interrupts have occurred.

(12-07-2016 12:08 AM)TravisE Wrote: I've read that passage in Insights as well, but as DavidM points out, I was under the impression that this brief processor wake-up would be pretty much
invisible to the user.

It's visible if you're looking at it as it happens. The display blinks on and back off all in a fraction of a second. As Ferris Bueller said, "Life moves pretty fast. If you don't stop and look around once in a while, you could miss it." Big Grin

(12-07-2016 12:08 AM)TravisE Wrote: I may be wrong, but I figure the display wouldn't even get turned on, and I wouldn't expect STARTOFF to be executed.

Yes, you are wrong. The display DOES turn on, albeit very briefly (unless other factors prolong it), and STARTOFF does in fact get executed.

(12-07-2016 12:08 AM)TravisE Wrote: If this were the case, then my HP 50g's with a STARTOFF routine that calls a backup program would have it executed at least every 3-ish days when not in use. But instead, the frequency of the apparent “phantom” STARTOFF calls I saw on one of my units is much more irregular.

If your STARTOFF is executed "much more irregular" than every 262144 seconds, then (a) something else is causing interrupts to occur, or (b) there is something in your STARTOFF program that is causing it to exit before the backup is performed, or (c) you have discovered an interesting new bug that involves executing a backup during the execution of STARTOFF. I hope it's c. Would you mind sharing your STARTOFF's listing with us?