EFM32WG Datasheet, PDF (130/834 Pages) List of Unclassifed Manufacturers – The EFM32WG Wonder Gecko is the ideal choice for demanding 8-, 16-, and 32-bit energy sensitive applications.

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Figure 11.3. CMU Switching from HFRCO to HFXO after HFXO is ready
CMU_CMD.HFCLKSEL
CMU_OSCENCMD.HFRCOEN
CMU_OSCENCMD.HFRCODIS
CMU_OSCENCMD.HFXOEN
CMU_OSCENCMD.HFXODIS
CMU_STATUS.HFRCORDY
CMU_STATUS.HFRCOENS
CMU_STATUS.HFRCOSEL
CMU_STATUS.HFXORDY
CMU_STATUS.HFXOENS
CMU_STATUS.HFXOSEL
HFCLK
HFRCO
HFXO
00
02
00
HFXO t im e-out period
Switching clock source for LFACLK and LFBCLK is done by setting the LFA and LFB fields in
CMU_LFCLKSEL. To ensure no stalls in the Low Energy Peripherals, the clock source should be ready
before switching to it.
Note
To save energy, remember to turn off all oscillators not in use.
11.3.3 Oscillator Configuration
11.3.3.1 HFXO and LFXO
The crystal oscillators are by default configured to ensure safe startup and operation of the most common
crystals. In order to optimize startup margin, startup time and power consumption for a given crystal, it is
possible to adjust the gain in the oscillator. HFXO gain can be increased by setting HFXOBOOST field
in CMU_CTRL, LFXO gain can be increased by setting LFXOBOOST field in CMU_CTRL or reduced
by setting REDLFXOBOOST field in EMU_AUXCTRL. It is important that the boost settings, along with
the crystal load capacitors are matched to the crystals in use. Correct values for these parameters can
be found using the energyAware Designer.
The HFXO crystal is connected to the HFXTAL_N/HFXTAL_P pins as shown in Figure 11.4 (p. 130)
Figure 11.4. HFXO Pin Connection
4-48 MHz
CL1
CL2
HFXTAL_N
HFXTAL_P
EFM3 2
2013-05-08 - Wonder Gecko Family - d0233_Rev0.50
130
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