Atmel Xplained Pro Evaluation Kit for the ATSAMD21J18A Microcontroller ATSAMD21-XPRO ATSAMD21-XPRO Data Sheet

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Atmel | SMART SAM D21 [DATASHEET]

Atmel-42181C–SAM-D21_Datasheet–07/2014

Sleep mode is activated by the Wait For Interrupt instruction (WFI). The Idle bits in the Sleep Mode register 
(SLEEP.IDLE) and the SLEEPDEEP bit of the System Control register of the CPU should be used as argument to select 
the level of the sleep mode.

There are two main types of sleep mode:

z

IDLE mode: The CPU is stopped. Optionally, some synchronous clock domains are stopped, depending on the 
IDLE argument. Regulator operates in normal mode.

z

STANDBY mode: All clock sources are stopped, except those where the RUNSTDBY bit is set. Regulator operates 
in low-power mode. Before entering standby mode the user must make sure that a significant amount of clocks 
and peripherals are disabled, so that the voltage regulator is not overloaded.

Notes:

1.

Asynchronous: interrupt generated on generic clock or external clock or external event.

2.

Synchronous: interrupt generated on the APB clock.

RESET CONTROLLER

BOD12

BOD33

POR

WDT

RESET

RESET SOURCES

RTC

32kHz clock sources

WDT with ALWAYSON

Generic Clock with 

WRTLOCK

Debug Logic

Others

CPU

RCAUSE

IDLE

0

SCR.SLEEPDEEP = 0
SLEEP.IDLE=Level
WFI

Synchronous

 (APB, AHB), asynchronous

1

Synchronous (APB), asynchronous

2

Asynchronous

STANDBY

SCR.SLEEPDEEP = 1
WFI

Asynchronous