19.6.3.3.3 BACKUP Mode

The BACKUP mode allows achieving the lowest power consumption aside from OFF. The device is entirely powered off except for the backup domain. All peripherals in backup domain are allowed to run, e.g. the RTC can be clocked by a 32.768kHz oscillator. All PM registers are reset except the CTRLA.IORET bit.

• Entering Backup mode: This mode is entered by executing the WFI instruction after selecting the Backup mode by writing the Sleep Mode bits in the Sleep Configuration register (SLEEPCFG.SLEEPMODE=BACKUP).
• Exiting Backup mode: is triggered when a Backup Reset is detected by the Reset Controller (RSTC).