10.3.1.5 LFACLK - Low Frequency A Clock
LFACLK is the selected clock for the Low Energy A Peripherals. There are three 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.
10.3.1.6 LFBCLK - Low Frequency B Clock
LFBCLK is the selected clock for the Low Energy B Peripherals. There are four 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 DeepSleep 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.
10.3.1.7 LFECLK - Low Frequency E Clock
LFECLK is the selected clock for the Low Energy E Peripherals. There are three selectable sources for LFECLK: LFRCO, LFXO and
ULFRCO. In addition, the LFECLK can be disabled, which is the default setting. The selection is configured using the LFE field in
CMU_LFECLKSEL.
The bus interface to the Low Energy E Peripherals is clocked by HFBUSCLK
LE
and this clock therefore needs to be enabled when
programming a LE peripheral.
Note:
LFECLK is in a different power domain than LFACLK and LFBCLK, which makes it available all the way down to EM4 Hibernate.
Each Low Energy Peripheral that is clocked by LFECLK has its own prescaler setting and enable bit. The prescaler settings are config-
ured using CMU_LFEPRESC0 and the clock enable bits can be found in CMU_LFECLKEN0.
10.3.1.8 PCNTnCLK - Pulse Counter n Clock
Each available pulse counter is driven by its own clock, PCNTnCLK where n is the pulse counter instance number. Each pulse counter
can be configured to use an external pin (PCNTn_S0) or LFACLK as PCNTnCLK.
10.3.1.9 WDOGCLK - Watchdog Timer Clock
The Watchdog Timer (WDOG) can be configured to use one of three different clock sources: LFRCO, LFXO or ULFRCO.
10.3.1.10 CRYOCLK - Cryotimer Clock
The Cryotimer clock can be configured to use one of three different clock sources: LFRCO, LFXO or ULFRCO. The Cryotimer can also
run in EM4 Hibernate/Shutoff provided that its selected clock is kept enabled as configured in EMU_EM4CTRL.
EFM32JG1 Reference Manual
CMU - Clock Management Unit
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