EFM32WG Datasheet, PDF (106/834 Pages) List of Unclassifed Manufacturers – The EFM32WG Wonder Gecko is the ideal choice for demanding 8-, 16-, and 32-bit energy sensitive applications.

10.3 Functional Description
...the world's most energy friendly microcontrollers
The Energy Management Unit (EMU) is responsible for managing the wide range of energy modes
available in EFM32WG. An overview of the EMU module is shown in Figure 10.1 (p. 106) .
Figure 10.1. EMU Overview
Peripheral bus
Cont rol and
status registers
Energy Managem ent
St at e Machine
Cort ex
Volt ag e
regulator
sy st em
Oscillat or
sy st em
Reset
sy st em
Mem ory
sy st em
In t er r u p t
controller
The EMU is available as a peripheral on the peripheral bus. The energy management state machine
is triggered from the Cortex-M4 and controls the internal voltage regulators, oscillators, memories and
interrupt systems in the low energy modes. Events from the interrupt or reset systems can in turn cause
the energy management state machine to return to its active state. This is further described in the
following sections.
10.3.1 Energy Modes
There are five main energy modes available in EFM32WG, called Energy Mode 0 (EM0) through Energy
Mode 4 (EM4). EM0, also called the active mode, is the energy mode in which any peripheral function
can be enabled and the Cortex-M4 core is executing instructions. EM1 through EM4, also called low
energy modes, provide a selection of reduced peripheral functionality that also lead to reduced energy
consumption, as described below.
Figure 10.2 (p. 107) shows the transitions between different energy modes. After reset the EMU will
always start in EM0. A transition from EM0 to another energy mode is always initiated by software. EM0
is the highest activity mode, in which all functionality is available. EM0 is therefore also the mode with
highest energy consumption.
The low energy modes EM1 through EM4 result in less functionality being available, and therefore also
reduced energy consumption. The Cortex-M4 is not executing instructions in any low energy mode.
Each low energy mode provides different energy consumptions associated with it, for example because
a different set of peripherals are enabled or because these peripherals are configured differently.
A transition from EM0 to a low energy mode can only be triggered by software.
A transition from EM1 – EM3 to EM0 can be triggered by an enabled interrupt or event. In addition, a
chip reset will return the device to EM0. A transition from EM4 can be triggered by a pin reset, power-
on reset, EM4 GPIO wakeup, or Backup RTC interrupt.
2013-05-08 - Wonder Gecko Family - d0233_Rev0.50
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