Bit
Name
Reset
Access Description
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=0 for RF performance. Set LOWPOWER=1 for non RF performance (not compatible with Radio opera-
tion).
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.
1
CMD
CMU_CMD HFXOPEAKDETSTART and HFXOSHUNTOPTSTART can
be used to trigger peak detection and shunt optimization sequences.
2
MANUAL
CMU_HFXOSTEADYSTATECTRL IBTRIMXOCORE, REGISH, RE-
GSELILOW, and PEAKDETEN are under full software control and are
allowed to be changed once HFXO is ready.
3:1
Reserved
To ensure compatibility with future devices, always write bits to 0. More information in
0
MODE
0
RW
HFXO Mode
Set this to configure the external source for the HFXO. The oscillator setting takes effect when 1 is written to HFXOEN in
CMU_OSCENCMD.
Value
Mode
Description
0
XTAL
38 MHz - 40 MHz crystal oscillator
1
EXTCLK
External clock can be supplied (square or wave) on HFXTAL_N pin.
Reference Manual
CMU - Clock Management Unit
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