Microcontrollers support DLMS meter international standards for smart meters
Renesas Electronics Europe has introduced new microcontrollers (MCUs) to the power meter market aimed particularly at smart meters.
The new RL78/I1C Group of MCUs is designed for the international standard DLMS with enhanced security function and improved arithmetic operation. The RL78/I1C group of MCUs also retains the measurement accuracy and low power consumption of its predecessor, the RL78/I1B group of which more than 30 million units have been shipped over three years.
Renesas developed the RL78/I1C MCUs for smart meters with DLMS support, leveraging key features from the current RL78/I1B Group of MCUs, such as low power consumption and numerous on-chip peripheral functions for reduced system cost.
These MCUs come in seven versions, with on-chip memory capacities ranging from 64KB for low-end single-phase meters, 128KB for high-end single-phase meters, and 256KB for three-phase meters; and package pin counts from 64 pins for space-saving needs, 80 pins for single-phase meters aimed for use in emerging developing countries to 100pins for single-phase meters aimed for use in advanced applications.
Key features of the RL78/I1C Group of MCUs include the ability to implement electric power measurement processing and DLMS processing on a single chip and it integrates an AES hardware engine for this purpose. In particular, the RL78/I1C is the power meter field industry’s first to implement in hardware the AES GCM mode required by the DLMS standard and thereby can deliver a speed boost of 20 times or more compared with encryption and decryption using software processing on existing Renesas MCUs.
In addition, the on-chip phase-locked loop (PLL) boosts the maximum operating frequency from 24 megahertz (MHz) to 32 MHz, and the 32bit multiplier/multiply-and-accumulate unit reduces the load imposed by software power calculation with 24-bit data converted by the 24-bit A/D converter, resulting in an approximate 30 per cent increase in arithmetic operation capacity. This means that a single chip can handle electric power measurement processing and DLMS processing.
The RL78/I1C MCUs can perform processing to support DLMS communication while simultaneously processing electric power measurement. Up to 256 KB of on-chip ROM can accommodate program code for electric power measurement processing and DLMS processing.
The MCUs support three-phase, four wire meters. The event link controller function and phase adjustment function coordinate the operation of the four-channel 24-bit A/D converter and three-channel 10-bit Successive Approximation Register (SAR) A/D converter. This enables current and voltage measurement on seven channels, as required in three-phase, four-wire meters. The addition of support for three-phase, four-wire meters, in addition to conventional single-phase, two-wire and three-phase, three-wire meters, allows meter manufacturers to utilise the RL78/I1C as a common platform to develop various meters from industrial to consumer.
In addition, Renesas has extended the features and functionality of the existing RL78/I1B to the new MCUs, along with improvements to the real-time clock that achieves a standby mode current consumption of 0.7microA (Typ.) during operation with independent power supply and power monitoring function with battery backup function that enable the CPU and peripheral functions to continue operating even when a power outage occurs.
By using the evaluation kit in the initial study phase, it is possible to start evaluating performance characteristics of the RL78/I1C without actually writing programs.
The reference kit, which includes hardware and drivers for measurement functions as well as a DLMS library, can be used in the meter development phase to reduce the time required for development by approximately 25 per cent, compared with independent development, and also to reduce costs, says the company
