The RL78/I1C microcontroller integrates functions required for the metrology of smart electricity meters. It includes 24-bit ΔΣ A/D converters, 32-bit multiply-accumulator, independent power supply real-time clock, segment LCD driver supporting up to 8 com, and AES hardware engine that supports the DLMS standard. For single-phase two-wire meters, single-phase three-wire meters, and three-phase three-wire meters, 24-bit ΔΣ A/D converters (Max 4ch) are used for current and voltage sensing to achieve highly accurate power metrology. Moreover, three-phase four-wire meters can be supported by the 100-pin QFP products, with ΔΣ A/D converters that are used for current sensing and a successive approximation A/D converter unit that is used for voltage sensing. In addition, the products equipped with 512KB flash memory can also use the code flash area as two partitions, that is 256KB x 2 banks, independently. Thanks to the bank programming function in dual-bank mode and bank swapping, the system can update the firmware without stopping the metrology operation throughout the new firmware downloading and even the bank swapping period.