25.5.3 Clocks

A 32 KHz or 1 KHz oscillator clock (CLK_RTC_OSC) is required to clock the RTC. The 32 KHz clock source can be FRC, POSC, SOSC or LPRC based on the mux selection controlled by the CFGCON4.VBKP_32KCSEL bit. The 1 KHz clock source is based on the mux selection controlled by the CFGCON4.VBKP_1KCSEL bit.

This oscillator clock is asynchronous to the bus clock (PB3_CLK). Due to this asynchronicity, writing to certain registers will require synchronization between the clock domains.