Energy Modes - Silicon Laboratories EFR32xG14 Wireless Gecko Reference Manual

11.3.4 Energy Modes

The availability of oscillators and system clocks depends on the chosen energy mode. Default the high frequency oscillators (HFRCO,
AUXHFRCO, and HFXO) and high frequency clocks (HFSRCLK, HFCLK, HFCORECLK, HFBUSCLK, HFPERCLK, HFRADIOCLK,
HFCLKLE) are available downto EM1 Sleep. From EM2 Deep Sleep onwards these oscillators and clocks are normally off, although
special cases exist as summarized in
Energy Mode Overview on page
and Figure 11.2 CMU Overview - Low Frequency Portion on page 281
energy modes.
The low frequency oscillators (LFRCO and LFXO) are available in all energy modes except in EM3 Stop when they are off by definition.
Default these oscillators are also off in EM4 Hibernate and EM4 Shutoff, but they can be retained on in these states as well if needed.
The ultra low frequency oscillator (ULFRCO) is default on in all energy modes, except for EM4 Shutoff, but it can be retained on in that
mode as well if needed. The low frequency clocks (LFACLK, LFBCLK, LFECLK, WDOGnCLK, RFSENSECLK, and CRYOCLK) are in
various power domains and therefore their availability not only depends on the chosen clock source, but also on the chosen energy
mode as indicated in Table 11.5 Oscillator and Clock Availability in Energy Modes on page
EM0 Active/EM1
Sleep
HFRCO 1
On
HFXO 1
On
AUXHFRCO 1
On
LFRCO, LFXO 1
On
ULFRCO On
HFSRCLK, HFCLK, 1
On
HFCORECLK,
HFBUSCLK,
HFPERCLK, HFRA-
DIOCLK, HFCLKLE
AUXCLK 1
On
ADCnCLK 1
On
LFACLK, LFBCLK
1
On
LFECLK 1
On
WDOGnCLK 1
On
CRYOCLK 1
On
1 Under software control.
2 Default off, but kept active if used by the ADC.
3 Default off, but can be retained on.
4 Will be kept on if AUXHFRCO is selected as clock source.
5 On only if ULFRCO is used as clock source.
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Table 11.5 Oscillator and Clock Availability in Energy Modes on page 303
215. The CMU overview figure in
Table 11.5. Oscillator and Clock Availability in Energy Modes
EM2 Deep Sleep
Off
Off
2
On
1
On
On
Off
2
On
4
On
1
On
1
On
1
On
1
On
Figure 11.1 CMU Overview - High Frequency Portion on page 280
also indicate which oscillators and clocks can be used in what
303.
EM3 Stop EM4 Hibernate
Off Off
Off Off
2 Off
On
Off
Retained on
On On
Off Off
2 Off
On
4 Off
On
Off
5
On
5
On Retained on
5 Off
On
5
On Retained on
Reference Manual
CMU - Clock Management Unit
and Table 10.2 EMU
EM4 Shutoff
Off
Off
Off
3 3
Retained on
3
Retained on
Off
Off
Off
Off
3 Off
Off
3 3
Retained on
Rev. 1.1 | 303