EM0
Active/EM1
Sleep
EM2 Deep
Sleep
EM3 Stop
EM4 Hiber-
nate
EM4 Shutoff
GPIO Pin State Retention
Yes
Yes
Yes
Available
1
Approximate time. Refer to the data sheet
2
Leaving the debugger connected when in EM2 or EM3 will cause the system to enter a higher power EM2 mode in which the high
frequency clocks are still enabled and certain core functionality is still powered-up in order to maintain debug-functionality.
3
The LDMA can be used with some low power peripherals (e.g., ADC, LEUART, LESENSE, CSEN) in EM2/3. Features required
by the LDMA which are not supported in EM2/3 (e.g., HFCLK), will be automatically enabled prior to the LDMA transfer and then
automatically disabled afterwards.
4
The RAC can be woken via a PRS interrupt to EM1 to transfer data. Once complete, the system will return to EM2.
5
While in EM2/3, an asynchronous event can be routed through PRS (e.g. GPIO IRQ or ACMP output) to wake up the ADC. Fea-
tures required by the ADC which are not supported in EM2/3 (e.g., AUXHFRCO) will be automatically enabled to allow the ADC to
convert a sample, and then automatically disabled afterwards.
6
I2C functionality limited to receive address recognition
7
Must be using ULFRCO
8
ACMP functionality in EM2/3 limited to edge interrupt
9
Pin wake-up in EM4 supported only on GPIO_EM4WUx pins. Consult data sheet for complete list of pins.
10 If enabled in EMU->EM4CTRL.EM4IORETMODE.
The different energy modes are summarized in the following sections.
10.3.1.1 EM0 Active
EM0 Active provides all system features.
• Cortex-M4 is executing code
• Radio functionality is available
• High and low frequency clock trees are active
• All oscillators are available
• All peripheral functionality is available
10.3.1.2 EM1 Sleep
EM1 Sleep disables the core but leaves the remaining system fully available.
• Cortex-M4 is in sleep mode. Clocks to the core are off
• Radio functionality is available
• High and low frequency clock trees are active
• All oscillators are available
• All peripheral functionality is available
Reference Manual
EMU - Energy Management Unit
silabs.com
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