 In terms of the core CPU, the EFM32 MCUs integrate the ARM Cortex-M series technology, spanning from the Cortex-M0+ to the Cortex-M4.To enable the Gecko MCU operation and take advantage of the ultralow power architecture, applications can operate with a main input clock rate of 4 MHz to 48 MHz.To reduce the need for external electronic components, the EFM32 integrates low frequency and ultralow frequency clocks as well.