67.9.1.1 Operation

The Backup mode is designed to serve prolonged power-down periods of the processor. In this mode, only the backup area of the device powered by VDDBU is maintained (RTC, GPBR, SHDWC, BSCR). This mode is entered by shutting down all the power rails of the device except VDDBU. It is good practice to use the SHDN output of the Shutdown Controller (SHDWC) for this purpose.

The SAM9X7 Series exits Backup mode when an active wake-up event is triggered by the Shutdown Controller (SHDWC). Upon this wake-up event, the SHDWC automatically toggles its SHDN output back to VDDBU and this signal typically helps to restart all the power supply channels at board level.