Depending on the application, peripherals may require specific clock frequencies to operate correctly. The Generic Clock controller (GCLK) features 5 Generic Clock Generators 0..4 that can provide a wide range of clock frequencies.

Generators can be set to use different external and internal oscillators as source. The clock of each Generator can be divided. The outputs from the Generators are used as sources for the Peripheral Channels, which provide the Generic Clock (GCLK_PERIPH) to the peripheral modules, as shown in Figure 2. The number of Peripheral Clocks depends on how many peripherals the device has.
Note: The Generator 0 is always the direct source of the GCLK_MAIN signal.