10.3.3 Exiting a Low Energy Mode
A system in EM2 Deep Sleep and EM3 Stop can be woken up to EM0 Active through regular interrupt requests from active peripherals.
Since state and RAM retention is available, the EFR32 is fully restored and can continue to operate as before it went into the Low Ener-
gy Mode.
Wake-Up from EM4 Hibernate or EM4 Shutoff is performed through reset. Wake-Up from a specific module must be enabled in that
module’s EM4WUEN register.
Enabled interrupts that can cause wake-up from a low energy mode are shown in
Table 10.3 EMU Wake-Up Triggers from Low Energy
. The wake-up triggers always return the EFR32 to EM0 Active/EM1 Sleep. Additionally, any reset source will re-
turn to EM0 Active. VMON-based EM4 Hibernate wake-ups also set the corresponding rise or fall interrupt flag. These flags serve as
the wake-up source for EM4 Hibernate and must be cleared by software on EM4 Hibernate exit. Not doing so will result in an immediate
wake-up after next EM4 Hibernate entry.
Table 10.3. EMU Wake-Up Triggers from Low Energy Modes
Peripheral
Wake-Up Trigger
EM2 Deep
Sleep
EM3 Stop
EM4 Hiber-
nate
EM4 Shut-
off
LEUART (Low Energy UART)
Receive / transmit
Yes
-
-
-
LETIMER
Any enabled interrupt
Yes
-
-
-
WDOG
Any enabled interrupt
Yes
Yes
-
-
LESENSE
Any enabled interrupt
Yes
-
-
-
LFXO
Ready Interrupt
Yes
-
-
-
LFRCO
Ready Interrupt
Yes
-
-
-
I
2
C
Receive address recognition
Yes
Yes
-
-
ACMP
Any enabled edge interrupt
Yes
Yes
-
-
ADC
SINGLE / SCAN FIFO events, window
comparator, and VREF overvoltage
Yes
Yes
-
-
VDAC
Any enabled interrupt except
EM23ERRIF
Yes
Yes
-
-
PCNT
Any enabled interrupt
Yes
Yes
-
-
RTCC
Any enabled interrupt
Yes
Yes
Yes
VMON
Rising or falling edge on any moni-
tored power
Yes
Yes
Yes
-
EMU Temperature Sensor
Measured temperature outside the de-
fined limits
Yes
Yes
Yes
-
CRYOTIMER
Timeout
Yes
Yes
Yes
Yes
Pin Interrupts
Transition
Yes
Yes
Yes
Yes
RFSENSE
RF signal detected
Yes
Yes
Yes
Yes
Reset Pin
Assertion
Yes
Yes
Yes
Yes
Power
Cycle Off/On
Yes
Yes
Yes
Yes
1
When using an external clock
2
Corresponding bit in the module's EM4WUEN must be set.
3
Only available on a subset of the pins. Refer to the data sheet for details.
Reference Manual
EMU - Energy Management Unit
silabs.com
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