Levels of restarting on a device

There are two levels of restarting that can occur on an Azure Sphere device:

• Device reboot: The MCU restarts and consequently resets peripherals, reconnects to the network layer, and restarts the applications and the Azure Sphere operating system (OS).
• Application restart: The application restarts, but peripherals, connection to the network layer, and the operating system remain in their current state.

The following circumstances cause a device to reboot:

• An update of the Azure Sphere OS is installed.
• An application update changes the peripheral configuration and the peripheral configuration is locked.
• The device is unplugged from the USB port and plugged in again.
• The Reset button on the device is pressed.
• The az sphere device restart CLI command is run.
• The PowerManagement_ForceSystemReboot function is called from a high-level application.

The following circumstances cause a high-level application or a real-time capable application to restart:

• An update of the application is installed.
• The application exits unexpectedly.
• An OS event or hardware event has occurred.
• The az sphere device app stop and az sphere device app start CLI commands are run.

Tasks that a high-level application should perform when starting or exiting are described in Initialization and termination. For details about when a high-level application or a real-time capable application should exit, see Lifecycle of an application.

For information about when a device checks for updates, see When do updates occur. Details about locking the peripheral configuration are described in Peripheral configuration locking.