The EFM™32, Energy Friendly Microcontrollers, is a family of 32-bit RISC Flash microcontrollers provided by Energy Micro AS. EFM32 is a mixed-signal microcontroller focusing on supporting ultra low power battery operated solutions. To be able to run off small cell batteries, EFM32 MCUs incorporates low power peripheral technology, fast response time and low latency, and autonomous operation (i.e the CPU does not run while the peripherals communicate). The EFM32 Gecko microcontrollers are offered in various configurations .
Steve Leibson presents EFM32 technology on his blog here
The central processing unit in EFM32 is the Cortex-M3 from ARM. This processor is one in a series of processors from ARM which was built for low power operation. Energy Micro announced its first large EFM32 customer in September 2008.