Bit
Name
Reset
Access Description
12:11
GAIN
0x2
RW
LFXO Startup Gain
The optimal value for maximum startup margin depends on the chosen XTAL. Refer to the device data sheet or Simplicity
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
1
BUFEXTCLK
An AC coupled buffer is coupled in series with LFXTAL_N pin, suitable
for external sinus wave (32768 Hz).
2
DIGEXTCLK
Digital external clock on LFXTAL_N pin. Oscillator is effectively by-
passed.
7
Reserved
To ensure compatibility with future devices, always write bits to 0. More information in
6:0
TUNING
0x00
RW
LFXO Internal Capacitor Array Tuning Value
Writing this field adjusts the internal load capacitance connected between LFXTAL_P and ground and LFXTAL_N and
ground symmetrically (the higher the value, the higher the capacitance, the lower the frequency). Only increment or decre-
ment by 1 LSB at a time.
Reference Manual
CMU - Clock Management Unit
silabs.com
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