23.5.3 Clocks

The OSCCTRL gathers controls for all device oscillators and provides clock sources to the Generic Clock Controller (GCLK). The available clock sources are XOSC, OSC16M, DFLLULP and FDPLL96M.

The OSCCTRL bus clock (CLK_OSCCTRL_APB) can be enabled and disabled in the Main Clock module (MCLK).

The control logic uses the oscillator output, which is also asynchronous to the user interface clock (CLK_OSCCTRL_APB). Due to this asynchronicity, writes to certain registers will require synchronization between the clock domains. Refer to 23.6.11 Synchronization for further details.

A generic clock (GCLK_DFLLULP) is required to clock the DFLLULP tuner in closed-loop operation. This clock must be configured and enabled in the generic clock controller before using the DFLLULP tuner. Refer to the Generic Clock Controller (GCLK) chapter for details.