RTC system doesn't work with LSI clock source

[george-metasphere]

When "Activating clock source" is ticked in RTC module, my MCU doesn't start up if I reset it from RST button. But as soon as I switch the RCC clock source to LSE external 32.768khz crystal and change RTC Clock Mux to LSE, it works without a hitch. Is this by design or there may be a bug?

[KDJEM.1]

Hello @george-metasphere ;

Could you please give more details about your configuration and project?

Are you testing a STM32CubeU3 firmware example? 

I tested the RTC_ALARM example in the STM32CubeU3 firmware. In this example the RTC work with LSI.

After I click on RESET button, I can see that LD2 is turned ON. So, the RTC Alarm is generated correctly.

Thank you.

Kaouthar