1.5 Clock Management During SleepWalking

Clock sources and GCLK generators can be autonomously woken up and switched off depending on the clocks requested by peripherals during standby (SleepWalking). During SleepWalking, the clock system responds differently depending on whether a peripheral requires an asynchronous (GCLK-based) or synchronous (APB/AHB-based) clock.

Table 1-3. Asynchronous vs. Synchronous Clock Requests
Request Type	Clocks Activated	Other Clocks	Use Case
Asynchronous (GCLK)	Peripheral's GCLK generator + associated clock source	All other clocks remain stopped	ADC sampling, AC comparison, timer counting
Synchronous (APB/AHB)	MCLK, GCLK Generator 0, associated clock source	Other AHB/APB clocks remain gated at MCLK output	DMA transfers, register access during SleepWalking