Bit
Name
Reset
Access Description
31:27
Reserved
To ensure compatibility with future devices, always write bits to 0. More information in
26:24
TIMEOUT
0x7
RW
LFXO Timeout
Configures the start-up delay for LFXO. Do not change while LFXO is enabled. When starting up the LFXO after it has been
completely turned off, use the TIMEOUT setting required by the XTAL. If the LFXO has been retained on in EM4, then the
TIMEOUT=2cycles configuration is also allowed when re-enabling the LFXO after EM4 exit (as it is still running).
Value
Mode
Description
0
2CYCLES
Timeout period of 2 cycles
1
256CYCLES
Timeout period of 256 cycles
2
1KCYCLES
Timeout period of 1024 cycles
3
2KCYCLES
Timeout period of 2048 cycles
4
4KCYCLES
Timeout period of 4096 cycles
5
8KCYCLES
Timeout period of 8192 cycles
6
16KCYCLES
Timeout period of 16384 cycles
7
32KCYCLES
Timeout period of 32768 cycles
23:21
Reserved
To ensure compatibility with future devices, always write bits to 0. More information in
20
BUFCUR
0
RW
LFXO Buffer Bias Current
The default value is intended to cover all use cases and reprogramming is not recommended. Do not change while LFXO is
enabled.
19:18
Reserved
To ensure compatibility with future devices, always write bits to 0. More information in
17:16
CUR
0x0
RW
LFXO Current Trim
The default value is intended to cover all use cases and reprogramming is not recommended. Do not change while LFXO is
enabled.
15
AGC
1
RW
LFXO AGC Enable
Set this bit to enable automatic gain control which limits XTAL oscillation amplitude. Do not change while LFXO is enabled.
14
HIGHAMPL
0
RW
LFXO High XTAL Oscillation Amplitude Enable
Set this bit to enable high XTAL oscillation amplitude. Do not change while LFXO is enabled.
13
Reserved
To ensure compatibility with future devices, always write bits to 0. More information in
12:11
GAIN
0x2
RW
LFXO Startup Gain
The optimal value for maximum startup margin depends on the chosen XTAL. Please refer to the Device Datasheet or Sim-
plicity Studio for more information.
10
Reserved
To ensure compatibility with future devices, always write bits to 0. More information in
9:8
MODE
0x0
RW
LFXO Mode
Set this to configure the external source for the LFXO. Do not change while LFXO is enabled. The oscillator setting takes
effect when 1 is written to LFXOEN in CMU_OSCENCMD. The oscillator setting is reset to default when 1 is written to
LFXODIS in CMU_OSCENCMD.
Value
Mode
Description
0
XTAL
32768 Hz crystal oscillator
EFM32JG1 Reference Manual
CMU - Clock Management Unit
silabs.com
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