24.13.8 Clock Selection

Name: CLKSEL
Offset: 0x07
Reset: 0x00
Property: -

Bit 76543210 
       CLKSEL[1:0] 
Access R/WR/W 
Reset 00 

Bits 1:0 – CLKSEL[1:0] Clock Select

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 XTAL32K1, 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 OSC32K 32.768 kHz from OSC32K
0x01 OSC1K 1.024 kHz from OSC32K
0x02 XTAL32K 32.768 kHz crystal oscillator
0x03 EXTCLK External clock from EXTCLK pin