STANDBY Mode

The STANDBY mode is the lowest power configuration while keeping the state of the logic and the content of the RAM.

In this mode, all clocks are stopped except those which are kept running if requested by a running peripheral or have the ONDEMAND bit written to "0". For example, the RTC can operate in STANDBY mode. In this case, its GCLK clock source will also be enabled.

All features that don’t require CPU intervention are supported in STANDBY mode. Here are examples:

• Autonomous peripherals features.
• Features relying on Event System allowing autonomous communication between peripherals.
• Features relying on on-demand clock.
• DMA transfers.
• Entering STANDBY mode: This mode is entered by executing the WFI instruction with the SLEEPCFG register written to STANDBY. The SLEEPONEXIT feature is also available as in IDLE mode.
• Exiting STANDBY mode: Any peripheral able to generate an asynchronous interrupt can wake up the system. For example, a peripheral running on a GCLK clock can trigger an interrupt. When the enabled asynchronous wake-up event occurs and the system is woken up, the device will either execute the interrupt service routine or continue the normal program execution according to the Priority Mask Register (PRIMASK) configuration of the CPU.

Depending on the configuration of these modules, the current consumption of the device in STANDBY mode can be slightly different.

The regulator operates in low-power mode (LP VREG) by default and can switch automatically to the main regulator if a task required by a peripheral requires more power. It returns automatically in the low power mode as soon as the task is completed.