10.3.2.1.4 HFXO
The HFXO can be enabled and disabled by software via the CMU_OSCENCMD register. The HFXO is disabled automatically when
entering EM2, EM3, or EM4. Hardware based HFXO enabling can be initiated by various peripherals as configured via the AUTOSTAR-
TEM0EM1, AUTOSTARTSELEM0EM1 bits in the CMU_HFXOCTRL register. The interaction between hardware based and software
based control of the HFXO is further explained in
After enabling the HFXO, it should not be disabled before it has been signaled to be enabled. Similarly, after disabling the HFXO it
should not be re-enabled before it has been signaled to be non-enabled. Typical enable and disable sequences are as follows:
CMU->OSCENCMD = CMU_OSCENCMD_HFXOEN;
while ((CMU->STATUS & CMU_STATUS_HFXOENS) != CMU_STATUS_HFXOENS);
CMU->OSCENCMD = CMU_OSCENCMD_HFXODIS;
while ((CMU->STATUS & CMU_STATUS_HFXOENS) == CMU_STATUS_HFXOENS);
EFM32JG1 Reference Manual
CMU - Clock Management Unit
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