10.3.10 EM23 Peripheral Retention Disable
Peripherals that are available in EM2 Deep Sleep or EM3 Stop can optionally be powered down during EM2 Deep Sleep or EM3 Stop.
This allows lower energy consumption in these energy modes. However, when powering down, these peripherals are independently
reset so the registers lose their configuration values. Therefore, they will have to be reconfigured upon wake-up to EM0 Active if they
were previously configured to non reset values.
EMU_EM23PERNORETAINCTRL register can be used to setup unused peripherals for powering down prior to EM23 entry. Once set-
up, upon EM23 entry, all peripherals in the power-down domain will get powered down if all of them are setup to be disabled.
Note:
User must ensure that the peripherals being powered down should have their clocks disabled in CMU prior to EM23 entry.
On waking up from EM23, EMU_EM23PERNORETAINSTATUS register indicates if the peripherals were powered down by the system
and subsequently locked out from register access. Locking out peripherals prevents users from accidentally using peripherals with con-
figurations at their reset state. EMU_EM23PERNORETAINCMD allows user to unlock these peripherals and hence grant access to
their registers for updating their configurations.
10.3.11 Brown Out Detector (BOD)
10.3.11.1 AVDD BOD
The EFR32 has a fast response Brown Out Detector (BOD) on AVDD that is always active. This BOD ensures the minimal supply is
provided to the AVDD supply (typically also connected to VREGVDD). Once triggered, the BOD will cause the system to reset.
Note:
In EM4 Hibernate/Shutoff a low power version of the AVDD BOD, called EM4BOD, is available to trigger a reset at level lower
than in other energy modes. All other BOD's are disabled during EM4 Hibernate/Shutoff
10.3.11.2 DVDD and DECOUPLE BOD
Additional BODs will monitor DVDD and DECOUPLE during EM0 Active through EM3 Stop. This can cause a reset to the internal logic,
but will not cause a power-on reset or reset the EMU or RTCC.
Reference Manual
EMU - Energy Management Unit
silabs.com
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