10.3.1 Energy Modes
EFR32 features six main energy modes, referred to as Energy Mode 0 (EM0 Active) through Energy Mode 4 (EM4 Shutoff). The Cor-
tex-M4 is only available for program execution in EM0 Active. In EM0 Active/EM1 Sleep any peripheral function can be enabled. EM2
Deep Sleep through EM4 Shutoff, also referred to as low energy modes, provide a significantly reduced energy consumption while still
allowing a rich set of peripheral functionality. The following
shows the possible transitions between differ-
ent energy modes.
Table 10.1. Energy Mode Transitions
Current Mode
EM Transition Action
Enter EM0 Ac-
tive
Enter EM1
Sleep
Enter EM2
Deep Sleep
EnterEM3
Stop
EnterEM4 Hi-
bernate
Enter EM4
Shutoff
EM0 Active
Sleep (WFI,
WFE)
Deep Sleep
(WFI, WFE)
Deep Sleep
(WFI, WFE)
EM4 Entry
EM4 Entry
EM1 Sleep
IRQ
Peripheral
wake up done
Peripheral
wake up done
EM2 Deep Sleep
IRQ
Peripheral
wake up req
EM3 Stop
IRQ
Peripheral
wake up req
EM4 Hibernate
Wake Up
EM4 Shutoff
Wake Up
1
Peripheral wake-up from EM2/3 to EM1 and then automatically back to EM2/3 when done.
The LESENSE, ADC, RAC, and LEUART have the ability to temporarily wake up the part from either EM2 Deep Sleep or EM3 Stop to
EM1 Sleep in order to transfer data. Once completed, the part is automatically placed back into the EM2 Deep Sleep or EM3 Stop
mode.
The Core can always request to go to EM1 Sleep with the WFI or WFE command during EM0 Active. The core will be prevented from
entering EM2 Deep Sleep or EM3 Stop if the RAC is transferring data or if Flash is programming or erasing.
An overview of supported energy modes and available functionality is shown in
Table 10.2 EMU Energy Mode Overview on page 215
.
For each energy mode, the system will typically default to its lowest power configuration, with non-essential clocks and peripherals disa-
bled. Functionality may be then selectively enabled by software.
Table 10.2. EMU Energy Mode Overview
EM0
Active/EM1
Sleep
EM2 Deep
Sleep
EM3 Stop
EM4 Hiber-
nate
EM4 Shutoff
Wake-up time to EM0 Active/EM1 Sleep
-
3 µs
90 µs
Core Active
Yes, in EM0
only
-
-
-
-
Debug
Available
See Note
See Note
-
-
Digital logic and system RAM retained
Yes
Yes
Yes
-
-
Flash Memory Access
Available
-
-
-
-
LDMA (Linked DMA Controller)
Available
Available
-
-
RAC (Radio Controller)
Available
Available
-
-
-
Reference Manual
EMU - Energy Management Unit
silabs.com
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