STM32H7 RTC in both M7 and M4 Dual Cores

[YSN]

I wanted to use RTC in both my cores M7 and M4. Is RTC a shared peripheral ? Can we use RTC to set or get time from any core asynchronously ?

Please share any configuration need to be done for doing so ?

[TDK]

Yes, it's shared, just like most (all?) of the other peripherals. You can access it from either core. Naturally, if you set it from one core, then set it from the other, you are overwriting the previous values.

RTC examples are in the CubeMX repository.

https://github.com/STMicroelectronics/STM32CubeH7/blob/ccb11556044540590ca6e45056e6b65cdca2deb2/Projects/STM32H7B3I-DK/Examples/RTC/RTC_Alarm/readme.txt

[YSN]

Fine, Overwriting is not a problem for me, but how about both cores accessing same RTC at same time, in such scenario should we use HSEM or is it already protected function ?

[TDK · Accepted solution]

Reading from the RTC at the same time is not a problem. Writing a new time needs a mechanism to ensure only one core does it at a time, such as HSEM. Preventing reading invalid values while the time is being updated could also use such a mechanism if desired.