I want to count clocks in order to implement a watch. I use the RTC0 as my time-base and count mainly with this device. As it has just 24 bits it would not last for long, which is why I use an extra counting variable that counts seconds (unix epoch time). My idea was to add the value of RTC0 to my counter in case of: I need to calculate the time now the RTC0 has an overflow After transfering the RTC0 value to my counter I want to clear the RTC as the value got transfered. But to make sure this works the clear must be synchronised to the RTC0 count increment. Otherwise I would loose the subdivision of my time hold in the prescaler. The other solution would be not to have the prescaler clear it's value but just the RTC counter.

This post is older than 2 years and might not be relevant anymore
More Info: Consider searching for newer posts

RTC clear event synchronised?

I want to count clocks in order to implement a watch. I use the RTC0 as my time-base and count mainly with this device. As it has just 24 bits it would not last for long, which is why I use an extra counting variable that counts seconds (unix epoch time). My idea was to add the value of RTC0 to my counter in case of:

I need to calculate the time now
the RTC0 has an overflow

After transfering the RTC0 value to my counter I want to clear the RTC as the value got transfered. But to make sure this works the clear must be synchronised to the RTC0 count increment. Otherwise I would loose the subdivision of my time hold in the prescaler. The other solution would be not to have the prescaler clear it's value but just the RTC counter.