10.3.2.2 Entry Into EM2 Deep Sleep or EM3 Stop
Energy mode EM2 Deep Sleep or EM3 Stop may be entered when
all
of the following conditions are true:
• Radio RAC state machine is in OFF state
• IDAC is currently not updating output.
• Cortex-M4 (if present) is in DEEPSLEEP state
• Flash Program/Erase Inactive
• DMA done with all current requests
• A debugger is not currently connected.
Entry into EM2 Deep Sleep and EM3 Stop can be blocked by setting the EMU_CTRL->EM2BLOCK bit.
Note:
When EM2 Deep Sleep or EM3 Stop entry is blocked, the part is not able to enter a lower energy state. The core will be in a
sleep state, similar to EM1, where it is waiting for a proper interrupt of other valid wake-up event. Once the blocking conditions are
removed, then the part will automatically enter a lower energy state.
Energy mode EM2 Deep Sleep is entered from EM0 Active when the Cortex-M4 executes the Wait For Interrupt (WFI) or Wait For
Event (WFE) instruction while the SLEEPDEEP bit in the Cortex-M4 System Control Register is set. The MCU can re-enter DeepSleep
automatically out of an Interrupt Service Routine (ISR) if the SLEEPONEXIT bit in the Cortex-M4 System Control Register is set. Refer
to ARM documentation on entering Sleep modes.
Alternately, EM2 Deep Sleep or EM3 Stop is entered from EM1 Sleep upon the completion of a Peripheral Wake-Up Request from the
RAC if no EM0 Active wake-up happens in the meantime.
10.3.2.3 Entry Into EM4 Hibernate or EM4 Shutoff
Energy mode EM4 Hibernate and EM4 Shutoff is entered through register access.
Software must ensure no modules are active,such as RAC, when entering EM4 Hibernate/Shutoff. EM4CTRL->EM4STATE field must
be configured to select either Hibernate (EM4H) or Shutoff (EM4S) mode prior to entering EM4.
Software may enter EM4 Hibernate/Shutoff from EM0 Active by writing the sequence 2,3,2,3,2,3,2,3,2 to EM4CTRL->EM4ENTRY bit
field. If the EM4BLOCK bit in WDOGn_CTRL is set, the CPU will be prevented from entering EM4 Hibernate/Shutoff by software re-
quest.
An active debugger connection will prevent entry into EM4 Hibernate/Shutoff.
Note that upon entry into EM4 Shutoff, the DC-DC converter configuration is reset to its default (i.e. Unconfigured) configuration. In the
Unconfigured configuration, the DC-DC converter will be disabled and the bypass switch will be turned off.
Reference Manual
EMU - Energy Management Unit
silabs.com
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