Energy Measurement on the MSP430 Energy Watchdog is performed using the MSP430AFE253. At the core of this Analog Front End (AFE) device is a 16-bit RISC architecture CPU with a system frequency of 12MHz. There is up to 16kB Flash and 512B RAM. The more traditional peripherals such as the 16-bit timer, watchdog, and hardware multiplier allow for custom controlled tasks and math intensive computations in ultra-low power modes. Possible communication interfaces include SPI and UART. The AFE is available in a 24-pin TSSOP package with 11 GPIOs that can also be configured with interrupt capability. At the heart of the analog front end are the 24-bit sigma-deltas. Designed for precise measurement applications, the Sigma-delta module integrates up to three independent 24-bit A/D converters. Each channel is designed with a fully differential analog input pair and programmable gain amplifier input stage. In addition to external analog inputs, internal VCC sense and temperature sensors are also available. The converters are based on second-order oversampling sigma-delta modulators and digital decimation filters. The decimation filters are comb type filters with selectable oversampling ratios of up to 1024.