30.4.1 Slow RC Oscillator (32 kHz typical)

By default, the Slow RC oscillator is enabled and selected as a source of SLCK.

Compared to the 32.768 kHz crystal oscillator, this oscillator offers a faster startup time and is less exposed to the external environment, as it is fully integrated. However, its output frequency is subject to larger variations with supply voltage, temperature and manufacturing process. Therefore, the user must take these variations into account when this oscillator is used as a time base (startup counter, frequency monitor, etc.). Refer to the section “Electrical Characteristics”.

This oscillator is disabled by clearing the SUPC_CR.XTALSEL.