@defgroup       cpu_efm32 Silicon Labs EFM32/EFR32/EZR32
@ingroup        cpu
@brief          Silicon Labs's EFM32/EFR32/EZR32 MCUs implementation

This module contains all code and definitions for the Silicon Labs
EFM32/EFR32/EZR32 MCUs. It uses the Gecko SDK (vendor library) for the
peripheral drivers.

Supported Peripherals
=====================

The following peripherals are supported (depends on microcontroller):
  - ADC
  - CPUID
  - DAC
  - Flash page
  - GPIO
  - HW RNG
  - I2C
  - Power Management
  - PWM
  - RTC
  - RTT
  - SPI
  - Timer
  - UART (including low-power)

Clock Configuration
===================

By default the microcontroller will run on the internal RC-oscillator. If
an external crystal is available, you can configure it to use by setting
`CLOCK_HF=cmuSelect_HFXO`. The same applies for `CLOCK_LFA`, `CLOCK_LFB` and
`CLOCK_LFE` using `cmuSelect_LFXO`.

If the internal RC-oscillator is not used, it will be disabled.

Refer to the reference manual of the specific microcontroller for the
specifics.

EMU and CMU Configuration
=========================

The Energy Management Unit (EMU) and Clock Management Unit (CMU) are
initialized using default values provided by the Gecko SDK. You can override
any of the following defaults to use other values:

  - `CMU_HFXOINIT`
  - `CMU_LFXOINIT`
  - `EMU_DCDCINIT`
  - `EMU_EM23INIT`
  - `EMU_EM4INIT`

Refer to the Gecko SDK for more information about these values.

Low-power Configuration
=======================

The EFM32/EFR32/EZR32 MCUs have support for low-power peripherals. Support
is enabled by default, but can be disabled if not used.

- Setting `EFM32_LEUART_ENABLED=0` will disable support for the LEUART
  in the UART driver peripheral and save approximately 400 bytes.
  Refer to `cpu/efm32/efm32-features.mk` for more options.

@defgroup       cpu_efm32gg Silicon Labs EFM32GG family
@ingroup        cpu_efm32
@brief          Silicon Labs's EFM32GG MCUs family implementation

@defgroup       cpu_efm32hg Silicon Labs EFM32HG family
@ingroup        cpu_efm32
@brief          Silicon Labs's EFM32HG MCUs family implementation

@defgroup       cpu_efm32lg Silicon Labs EFM32LG family
@ingroup        cpu_efm32
@brief          Silicon Labs's EFM32LG MCUs family implementation

@defgroup       cpu_efm32pg1b Silicon Labs EFM32PG1B family
@ingroup        cpu_efm32
@brief          Silicon Labs's EFM32PG1B MCUs family implementation

@defgroup       cpu_efm32pg12b Silicon Labs EFM32PG12B family
@ingroup        cpu_efm32
@brief          Silicon Labs's EFM32PG12B MCUs family implementation

@defgroup       cpu_efm32zg Silicon Labs EFM32ZG family
@ingroup        cpu_efm32
@brief          Silicon Labs's EFM32ZG MCUs family implementation

@defgroup       cpu_efr32mg1b Silicon Labs EFR32MG1P family
@ingroup        cpu_efm32
@brief          Silicon Labs's EFR32MG1B MCUs family implementation

@defgroup       cpu_efr32mg1p Silicon Labs EFR32MG1P family
@ingroup        cpu_efm32
@brief          Silicon Labs's EFR32MG1P MCUs family implementation

@defgroup       cpu_efr32mg12p Silicon Labs EFR32MG12P family
@ingroup        cpu_efm32
@brief          Silicon Labs's EFR32MG12P MCUs family implementation

@defgroup       cpu_ezr32wg Silicon Labs EZR32WG family
@ingroup        cpu_efm32
@brief          Silicon Labs's EZR32WG MCUs family implementation