Silicon Laboratories EFR32xG21 Wireless Gecko Reference Manual page 256

Note:
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., IADC) in EM2/3. Features required by the LDMA which are not
supported in EM2/3 (e.g., HCLK), will be automatically enabled prior to the LDMA transfer and then automatically disabled after-
wards.
4. The RAC can be woken via a PRS interrupt to EM1 to transfer data. Once complete, the system will return to EM2.
5. Default off, but kept active if used by the IADC.
6. Default off, but kept active if used by the BURTC
7. Must be using ULFRCO
8. I2C0 only. Not supported on all GPIO Ports. Functionality limited to receive address recognition
9. ACMP functionality in EM2/3 limited to edge interrupt
10. Pin wake-up in EM4 supported only on GPIO_EM4WUx pins. Consult data sheet for complete list of pins.
11. If enabled in EMU->EM4CTRL.EM4IORETMODE.
12. PRS in EM4 supported only on EM4 capable pins. Consult data sheet for complete list of EM4 capable pins.
13. Module is in the Low Power Domain B (LPDB). The entire LPDB will be kept on in EM2/3 (resulting in higher current draw) if any
module in LPDB is enabled on EM2/3 entry.
The different energy modes are summarized in the following sections.
12.3.1.1 EM0
EM0 provides all system features.
• Cortex-M33 is executing code
• Radio functionality is available
• High and low frequency clock trees are active
• All oscillators are available
• All peripheral functionality is available
12.3.1.2 EM1
EM1 disables the core but leaves the remaining system fully available.
• Cortex-M33 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
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EM0 Active/EM1 Sleep EM2
Reference Manual
EMU - Energy Management Unit
EM3 EM4
Rev. 0.4 | 256