Hi,
I have observed that after going to sleep and waking up, my timer 0 interrupt handler does not get called.

My problem is this:

My micro receives an external interrupt every second from a real time clock. This external interrupt is tied to /INT0 of the micro.

I need to light up an LED for 10 seconds(visual alarm). I calculated how many times timer 0 would overflow in 10 seconds. Let us call this count 'n'. Then in my timer 0 ISR, I keep a count how many times the ISR was called. When this number matches 'n' I know that 10 seconds have elapsed and then I shut the LED down.

The problem I am facing is that if I go to power down mode between the RTC interrupts, my LED keeps on blinking and never stops. Basically the count 'n' is never reached.

However, if I choose to go to idle mode instead of power down mode, everything works and my LED does not light up after 10 seconds.

Somehow I believe that this is due to the oscillator stopping in power down mode and not stopping in idle mode. But I am not able to figure out the exact connection.

Can anyone please suggest what is happening here?


Thanks in advance!

regards,
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