Writing these bits select the source for the RTC clock (CLK_RTC).
When configuring the RTC to use either XOSC32K or the
external clock on TOSC1, XOSC32K needs to be enabled, and the Source Select
(SEL) bit and Run Standby (RUNSTDBY) bit in the XOSC32K Control A of the
Clock Controller (CLKCTRL.XOSC32KCTRLA) register must be configured
accordingly.
| Value | Name | Description |
|---|
0x00 | INT32K | Internal 32.768 kHz oscillator |
0x01 | INT1K | Internal 1.024 kHz oscillator |
0x02 | TOSC32K | 32.768 kHz crystal oscillator |
0x03 | EXTCLK | External clock from EXTCLK pin |
