Silicon Laboratories EFR32xG14 Wireless Gecko Reference Manual page 296

RAC wake-up with CMU_HFXOCTRL.AUTOSTARTRDYSELRAC = 1
EM0/EM1 entry with CMU_HFXOCTRL.AUTOSTARTSELEM0EM1 = 1
CMU_STATUS.HFRCORDY
CMU_STATUS.HFRCOENS
CMU_HFCLKSTATUS.HF = HFRCO
CMU_STATUS.HFXORDY
CMU_STATUS.HFXOENS
CMU_HFCLKSTATUS.HF = HFXO
If an automatic selection of HFXO is performed, which switches the clock source used for HFSRCCLK, then the HFXOAUTOSW bit in
CMU_IF is set to 1. After automatic enable and selection of the HFXO, the HFRCO is automatically disabled in case it is running. The
disabling of a running HFRCO is signalled via the HFRCODIS bit in CMU_IF. This only applies to the HFRCO. If for example the LFXO
was used as HFSRCCLK at the time of automatic selection of the HFXO, the LFXO remains unaffected.
The interaction between automatic HFXO startup and selection with startup and selection of HFRCO is shown in
HFRCO startup/selection while awaiting automatic HFXO startup/selection on page 296
up/selection while HFRCO started/selected on page
RAC wake-up with CMU_HFXOCTRL.AUTOSTARTRDYSELRAC = 1
||
EM0/EM1 entry with CMU_HFXOCTRL.AUTOSTARTSELEM0EM1 = 0
CMU_STATUS.HFRCORDY
CMU_STATUS.HFRCOENS
CMU_HFCLKSTATUS.HF = HFRCO
CMU_STATUS.HFXORDY
CMU_STATUS.HFXOENS
CMU_HFCLKSTATUS.HF = HFXO
HFCLK
HFRCO
HFXO
Figure 11.9. CMU HFRCO startup/selection while awaiting automatic HFXO startup/selection
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||
HFCLK
HFRCO
HFXO
Figure 11.8. CMU Automatic Startup and Selection of HFXO
297.
EM0/EM1 Entry
&&
CMU_HFXOCTRL.AUTOSTARTSELEM0EM1 = 0
HFXO ready Automatic switch to HFXO (and disable of HFRCO)
and Figure 11.10 CMU Automatic HFXO start-
HFRCO selected HFXO ready
Reference Manual
CMU - Clock Management Unit
Figure 11.9 CMU
Automatic switch to HFXO and disable of HFRCO
Rev. 1.1 | 296