12.3.2.1 Sleep Modes

Three different sleep modes can be enabled to reduce power consumption.

Idle
The CPU stops executing code, resulting in reduced power consumption.
All peripherals are running, and all interrupt sources can wake the device.
Standby
All high-frequency clocks are stopped apart from any peripheral or clock that are enabled to run in Standby sleep mode. This is enabled by writing the corresponding RUNSTDBY bit to ‘1’. The power consumption is dependent on the enabled functionality.
A subset of interrupt sources can wake the device(1).
Power-Down
All high-frequency clocks are stopped, resulting in a power consumption lower than the Idle sleep mode.
A subset of the peripherals are running, and a subset of interrupt sources can wake the device(1).
Note:
  1. Refer to the Sleep Mode Activity tables for further information.

Refer to the Wake-up Time section for information on how the wake-up time is affected by the different sleep modes.

Table 12-1. Sleep Mode Activity Overview for Peripherals
ClockPeripheralActive in Sleep Mode
IdleStandbyPower-Down
CLK_CPU CPU---
CLK_RTCRTCXX(1,2)X(2)
CLK_WDTWDTXXX
CLK_BOD(3)BODXXX
(4)CCLXX(1)-
CLK_PERADCnXX(1)-
TCAn
TCBn
All other peripheralsX--
Note:
  1. Set the RUNSTDBY bit of the corresponding peripheral to enter an active state.
  2. In Standby sleep mode, only the RTC functionality requires the RUNSTDBY to be set to enter an active state. In Power-Down sleep mode, only the PIT functionality is available.
  3. Sampled mode only.
  4. The clock domain depends on the clock source selected for CCL.
Table 12-2. Sleep Mode Activity Overview for Clock Sources
Clock SourceActive in Sleep Mode
IdleStandbyPower-Down
Main clock sourceXX(1)-
RTC clock sourceXX(1,2)X(2)
WDT oscillatorXXX
BOD oscillator(3)XXX
CCL clock sourceXX(1)-
Note:
  1. Write the RUNSTDBY bit of the corresponding peripheral to enter an active state.
  2. In Standby sleep mode, only the RTC functionality requires the RUNSTDBY to be set to enter an active state. In Power-Down sleep mode, only the PIT functionality is available.
  3. Sampled mode only.
Table 12-3. Sleep Mode Wake-Up Sources
Wake-Up SourceActive in Sleep Mode
IdleStandbyPower-Down
PORT Pin interruptXXX(1)
TWI Address Match interruptXXX
BOD VLM interruptXXX
CCL interruptsXX(2,3)X(3)
RTC interruptsXX(2,4)X(4)
USART interruptsX(5)X(6)-
TCAn interruptsXX(2)-
TCBn interrupts
ADCn interrupts
ACn Compare interrupt
All other interruptsX--
Note:
  1. The I/O pin must be configured according to Asynchronous Sensing Pin Properties in the PORT section.
  2. Set the RUNSTDBY bit of the corresponding peripheral to enter an active state.
  3. CCL can wake up the device if the path through LUTn is asynchronous (FILTSEL=0x0 and EDGEDET=0x0 in LUTnCTRLA register).
  4. In Standby sleep mode, only the RTC functionality requires the RUNSTDBY to be set to enter an active state. In Power-Down sleep mode, only the PIT functionality is available.
  5. Start-of-Frame interrupt is only available in Standby sleep mode.
  6. In Standby sleep mode, only the Start-of-Frame interrupt will trigger Wake-Up from USART.