EFM32 Zero Gecko 32-bit Microcontrollers Silicon Labs EFM32 Zero Gecko 32-bit Microcontrollers are the latest addition to the Silicon Labs Gecko portfolio of ultra-low-power and energy-friendly 32-bit microcontrollers (MCUs). The EFM32 MCUs are the world's most energy-friendly microcontrollers. With a unique combination of the powerful 32-bit ARM Cortex-M0+, innovative low energy techniques, short wake-up time from energy saving modes, and a wide selection of peripherals, the EFM32ZG microcontroller is well suited for any battery-operated application as well as other systems requiring high performance and low energy consumption.