Sleep Modes

In addition to Active mode, there are three different sleep modes, with decreasing power consumption and functionality.

The CPU stops executing code, no peripherals are disabled.
All interrupt sources can wake up the device.
The user can configure peripherals to be enabled or not, using the respective RUNSTBY bit. This means that the power consumption is highly dependent on what functionality is enabled, and thus may vary between the Idle and Power-Down levels.
SleepWalking is available for the ADC module.
The wake-up sources are pin interrupts, TWI address match, UART Start-of-Frame interrupt (if USART is enabled to run in Standby), RTC interrupt (if RTC enabled to run in Standby), and TCB interrupt.
Only the WDT and the PIT (a component of the RTC) are active.
The only wake-up sources are the pin change interrupt and TWI address match.
Table 1. Sleep Mode Activity Overview
Group Peripheral Active in Sleep Mode
  Clock Idle Standby Power-Down
Oscillators Main Clock Source X X*  
RTC Clock Source X X*  
WDT Oscillator X X X
Wake-Up Sources INTn and Pin Change X X X
TWI Address Match X X X
Periodic Interrupt Timer X X X
UART Start-of-Frame X X*  
ADC Window X X*  
RTC Interrupt X X*  
All other Interrupts X