The UART clock can be controlled through the Power Management Controller (PMC). In this case, the user must first configure the PMC to enable the UART clock. Usually, the peripheral identifier used for this purpose is 1.
In SleepWalking mode (asynchronous partial wake-up), the PMC must be configured to enable SleepWalking for the UART in the Sleepwalking Enable Register (PMC_SLPWK_ER). Depending on the instructions (requests) provided by the UART to the PMC, the system clock may or may not be automatically provided to the UART.