4.15.4 Functional Description

The TD_OSCSEL bit located in the Slow Clock Controller Configuration register (SCKC_CR) is in the backup domain and its value is kept while VBAT is present.

The embedded Always-on 64 kHz (typical) slow RC oscillator is always enabled as soon as VBAT is established. The Slow Clock Selector command TD_OSCSEL bit selects the slow clock source of the RTT and the RTC.

After the VBAT Power-On-Reset, the default configuration is TD_OSCSEL = 0.

The programmer controls the slow clock switching by software, so precautions must be taken during the switching phase.