Refer to the PDF data sheet for device specific package drawings
Figure 7-27 shows the recommended oscillator connections when WKUP_OSC0_XI is connected to a 1.8-V LVCMOS square-wave digital clock source.
A DC steady-state condition is not allowed on WKUP_OSC0_XI when the oscillator is powered up. This is not allowed because WKUP_OSC0_XI is internally AC coupled to a comparator that may enter a unknown state when DC is applied to the input. Therefore, application software should power down WKUP_OSC0 any time WKUP_OSC0_XI is not toggling between logic states.