Bit
Name
Reset
Access Description
31:30
Reserved
To ensure compatibility with future devices, always write bits to 0. More information in
29
AUTOSTARTSE-
LEM0EM1
0
RW
Automatically start and select of HFXO upon EM0/EM1 entry from
EM2/EM3
This bit enables automatic start-up and immediate selection of the HFXO when in EM0/EM1 (also after entry from EM2/
EM3). Note that setting this bit to 1 will stall HFSRCCLK until HFXO becomes ready. Allowed to change at any time.
28
AUTOSTAR-
TEM0EM1
0
RW
Automatically start of HFXO upon EM0/EM1 entry from EM2/EM3
This bit enables automatic start-up of the HFXO when in EM0/EM1 (also after entry from EM2/EM3) without causing an
automatic HFXO selection. Allowed to change at any time.
27
Reserved
To ensure compatibility with future devices, always write bits to 0. More information in
26:24
LFTIMEOUT
0x0
RW
HFXO Low Frequency Timeout
Configures the start-up delay for HFXO measured in LFECLK cycles. Only change when both HFXO and LFECLK are off.
Value
Mode
Description
0
0CYCLES
Timeout period of 0 cycles (disabled)
1
2CYCLES
Timeout period of 2 cycles
2
4CYCLES
Timeout period of 4 cycles
3
16CYCLES
Timeout period of 16 cycles
4
32CYCLES
Timeout period of 32 cycles
5
64CYCLES
Timeout period of 64 cycles
6
1KCYCLES
Timeout period of 1024 cycles
7
4KCYCLES
Timeout period of 4096 cycles
23:11
Reserved
To ensure compatibility with future devices, always write bits to 0. More information in
10
XTO2GND
0
RW
Clamp HFXTAL_P pin to ground when HFXO oscillator is off.
Set to enable grounding of HFXTAL_P pin when HFXO oscillator is off
9
XTI2GND
0
RW
Clamp HFXTAL_N pin to ground when HFXO oscillator is off.
Set to enable grounding of HFXTAL_N pin when HFXO oscillator is off. Do not enable if MODE=EXTCLK and an external
source is supplied.
8
LOWPOWER
0
RW
Low power mode control.
Set LOWPOWER=1 to enable low current consumption.
7:6
Reserved
To ensure compatibility with future devices, always write bits to 0. More information in
5:4
PEAKDETSHUN-
TOPTMODE
0x0
RW
HFXO Automatic Peak Detection and shunt current optimization
mode
Set to AUTOCMD to allow automatic HFXO peak detection and shunt current optimization (MANUAL mode provides direct
control of IBTRIMXOCORE, REGISH, PEAKDETEN, REGSELILOW).
Value
Mode
Description
0
AUTOCMD
Automatic control of HFXO peak detection and shunt optimization se-
quences. CMU_CMD HFXOPEAKDETSTART and HFXOSHUNTOPT-
START can also be used.
EFM32JG1 Reference Manual
CMU - Clock Management Unit
silabs.com
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