The STPM01 and STPM10 devices are energy meter ASSPs (Application Specific Standard Products) designed to address a wide range of electricity metering requirements thanks to their built-in functionalities as signal conditioning, signal processing, data conversion, input/output signals and voltage reference. STPM10 is dedicated for peripheral use only in microcontroller based applications, while STPM01 is able to work as a peripheral but also as a standalone device, since it can permanently store configuration and calibration data. Both the devices have an SPI port to write configuration parameters and read all the information on the line energy from their internal registers. Measured data (like active, reactive and apparent energy, VRMS, IRMS, instantaneous voltage and current, line frequency, device status etc.) should be read by the microcontroller at a fixed time interval to be further processed. This application note describes the SPI protocol to read measured data from STPM01 and STPM10 in a single-phase energy meter and how these readings should be processed by the application.