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RTC Wakeup Interrupt latency

Question asked by Yevpator on Oct 22, 2012
Dear,

I'm developing now on STM8L151C8.
On the very beginning of my project i measured how much time takes from Wakeup from Halt to RTC interrupt and, if my memory does not fail me, it was less than 1uses, exactly like it should be according to the Datasheet, i.e. working with HSI=16MHz with latency of 8 or 12 cycles(don't remember the value), i should see less than 1usec. But now I've just paid attention that it takes 7-8 usec to get to the interrupt and 7-8us to exit. I thought may be the osc is not stable and working slower than 16MHz at the beginning of the Wakeup and thus I get 7usec latency, but the fact is that HSI is stable and accurate, so I don't know where  these 7usec are wasted. Also I've checked if another interrupt preceding RTC wakeup, causing this delay, but this option has been declined too.

I would appreciate any idea.
Best regards,
E.L.

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