EFR32MG21 Mighty Gecko Series 2 Wireless SoCs Silicon Labs EFR32MG21 Mighty Gecko Series 2 Multiprotocol Wireless SoCs offer an 80MHz ARM Cortex-M33 core with a dedicated security core that provides faster encryption, secure boot loading, and debug access control. The EFR32MG21 are designed to increase processing capability, improve RF performance, and lower active current, while providing a higher level of security.