Bit
Name
Reset
Access Description
0x7
HFOSC1_DIV_1P5
Clock derived from the Internal High Frequency Oscillator 1, pre-scaled
by 1.5.
This device family has restrictions when switching to clock sources that are greater than 25 MHz. SYSCLK must be running at a fre-
quency of 24 MHz or greater before switching the CLKSL field to HFOSC1. When transitioning from slower clock frequencies, firm-
ware should make two writes to CLKSEL.
8.4.2 HFO0CAL: High Frequency Oscillator 0 Calibration
Bit
7
6
5
4
3
2
1
0
Name
HFO0CAL
Access
RW
Reset
Varies
SFR Page = 0x0, 0x10; SFR Address: 0xC7
Bit
Name
Reset
Access Description
7:0
HFO0CAL
Varies
RW
Oscillator Calibration.
These bits determine the period for high frequency oscillator 0. When set to 0x00, the oscillator operates at its fastest set-
ting. When set to 0xFF, the oscillator operates at its slowest setting. The reset value is factory calibrated, and the oscillator
will revert to the calibrated frequency upon reset.
8.4.3 HFO1CAL: High Frequency Oscillator 1 Calibration
Bit
7
6
5
4
3
2
1
0
Name
Reserved
HFO1CAL
Access
R
RW
Reset
0
Varies
SFR Page = 0x10; SFR Address: 0xD6
Bit
Name
Reset
Access Description
7
Reserved
Must write reset value.
6:0
HFO1CAL
Varies
RW
Oscillator Calibration.
These bits determine the period for high frequency oscillator 1. When set to 0x00, the oscillator operates at its fastest set-
ting. When set to 0x7F, the oscillator operates at its slowest setting. The reset value is factory calibrated, and the oscillator
will revert to the calibrated frequency upon reset.
EFM8UB3 Reference Manual
Clocking and Oscillators
silabs.com
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