11.3.1.5 HFRADIOCLK - High Frequency Radio Clock
HFRADIOCLK is a prescaled version of HFCLK which drives the High-Frequency Radio Peripherals. All the radio peripherals that are
driven by this clock can be clock gated completely when not in use. This is done by clearing the clock enable bit for the specific periph-
eral in CMU_HFRADIOCLKEN0. The radio peripherals can also be gated simultaneously by clearing the HFRADIOCLKEN bit in the
CMU_CTRL register. The prescale factor for prescaling HFCLK into HFRADIOCLK is set using the CMU_HFRADIOPRESC register.
The setting can be changed dynamically and the new setting takes effect immediately.
Note:
If HFRADIOCLK runs faster than HFCORECLK, the number of clock cycles for each bus-access to radio peripheral modules will in-
crease with the ratio between the clocks. E.g. if a bus-access normally takes three cycles, it will take 9 cycles if HFRADIOCLK runs
three times as fast as the HFCORECLK.
11.3.1.6 ADCnCLK - ADC Core Clock
ADCnCLK is a selectable core clock for ADCn. There are three selectable sources for ADCnCLK: HFSRCCLK, HFXO and AUXHFR-
CO. In addition, the ADCnCLK can be disabled, which is the default setting. The selection is configured using the ADCnCLKSEL field in
CMU_ADCCTRL. The ADCnCLKINV bit in CMU_ADCCTRL can be used to invert ADCnCLK. The ADCnCLKDIV bitfield in
CMU_ADCCTRL can be used to prescale ADCnCLK. The bus interface of ADCn is clocked with HFBUSCLK.
11.3.1.7 LFACLK - Low Frequency a Clock
LFACLK is the selected clock for the Low Energy A Peripherals. There are several selectable sources for LFACLK: LFRCO, LFXO and
ULFRCO. In addition, the LFACLK can be disabled, which is the default setting. The selection is configured using the LFA field in
CMU_LFACLKSEL.
The bus interface to the Low Energy A Peripherals is clocked by HFBUSCLK
LE
and this clock therefore needs to be enabled when
programming a Low Energy (LE) peripheral.
Each Low Energy Peripheral that is clocked by LFACLK has its own prescaler setting and enable bit. The prescaler settings are config-
ured using CMU_LFAPRESC0 and the clock enable bits can be found in CMU_LFACLKEN0.
When operating in oversampling mode, the pulse counters are clocked by LFACLK. This is configured for each pulse counter (n) indi-
vidually by setting PCNTnCLKSEL in CMU_PCNTCTRL.
11.3.1.8 LFBCLK - Low Frequency B Clock
LFBCLK is the selected clock for the Low Energy B Peripherals. There are several selectable sources for LFBCLK: LFRCO, LFXO,
HFCLKLE and ULFRCO. In addition, the LFBCLK can be disabled, which is the default setting. The selection is configured using the
LFB field in CMU_LFBCLKSEL. The HFCLKLE setting allows the Low Energy B Peripherals to be used as high-frequency peripherals.
The bus interface to the Low Energy B Peripherals is clocked by HFBUSCLK
LE
and this clock therefore needs to be enabled when
programming a LE peripheral.
Note:
If HFCLKLE is selected as LFBCLK, the clock will stop in EM2 Deep Sleep and EM3 Stop.
Each Low Energy Peripheral that is clocked by LFBCLK has its own prescaler setting and enable bit. The prescaler settings are config-
ured using CMU_LFBPRESC0 and the clock enable bits can be found in CMU_LFBCLKEN0.
Reference Manual
CMU - Clock Management Unit
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