LFXTAL and LFOSC can be the source for the LF_CLK mux. By default, LFOSC is selected as the source for this mux.
- LF_CLK is used as the source clock for RTC1 and Beeper.
- RTC0 is always sourced by the LFXTAL
- WDT is always sourced by the LFOSC
Note that the LFXTAL should be enabled before changing the LF_CLK mux to 1.