Renesas microcontrollers boost security for smart meters
September 13, 2016
Japanese electronics giant Renesas has introduced a group of microcontrollers that it says can improve security and arithmetic operation of smart power meters.
The RL78/I1C MCUs are designed for the international standard DLMS (Device Language Message Specification), an IEC standard used by power companies for exchanging meter data. They also retain the measurement accuracy and low power consumption of its predecessor, the RL78/I1B, of which more than 30 million units have been shipped over three years.
Demand for electric power has increased worldwide in recent years, and the adoption of smart meters has spread rapidly to encourage energy conservation, support the liberalisation of the power industry, and prevent electricity theft. The number of installations per year of smart meters with enhanced security features such as DLMS support is expected to grow from 30 million in 2016 to 110 million in 2020 worldwide.
Ensuring the security of power meter data and lowering meter prices have become key issues amid this sudden increase in the number of smart meters in use. As a result, power meter manufacturers are calling for improved security features to support DLMS and reduced development cost by using common platforms for various meter systems.
To address these needs, Renesas developed the RL78/I1C MCUs with DLMS support, leveraging key features from the current RL78/I1B, such as low power consumption and numerous on-chip peripheral functions for reduced cost.
The MCUs are available in seven versions, with on-chip memory capacities ranging from 64kbyte for low-end single-phase meters and 128kbyte for high-end single-phase meters to 256kbyte 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 countries, to 100 pins for single-phase meters for use in advanced applications.
Smart meters require authentication and encryption-decryption functions that conform to the DLMS standard when transferring power meter data measured using a power-measurement MCU to the communications block. The RL78/I1C integrates an AES hardware engine for this purpose.
In particular, it claims to be the first to implement in hardware the AES GCM cryptographic mode required by the DLMS standard, and thereby delivers 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 increases the maximum operating frequency from 24 to 32MHz, and the 32bit multiplier-multiply-and-accumulate unit reduces the load imposed by software power calculation with 24bit data converted by the 24bit A-D converter, resulting in an approximate 30 per cent increase in arithmetic operation capacity. This means a single chip can handle both electric power measurement processing and DLMS processing.
The MCUs can perform processing to support DLMS communications while simultaneously processing electric power measurement. Up to 256kbyte of on-chip ROM can accommodate programme code for both electric power measurement processing and DLMS processing. This leads to approximately 30 per cent reduced power consumption compared with a two-chip configuration and reduced cost compared with earlier two-chip sets comprised of power measurement and dedicated DLMS processing MCUs.
The event link controller and phase adjustment function coordinate the operation of the four-channel 24bit A-D converter and three-channel 10bit successive approximation register 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 use the device 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 0.7μA typical during operation with independent power supply and power monitoring with battery backup function that enable the CPU and peripheral functions to continue operating even when a power outage occurs.
Demand for power meters is growing rapidly in worldwide markets, especially emerging economies. This calls for quicker time to development for new meter models and using the current expertise more efficiently. By using the meter analogue evaluation kit in the initial study phase, it is possible to start evaluating performance characteristics of the device without actually writing programmes. The meter 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 about 25 per cent compared with independent development, and to reduce costs.
Samples are available now. Mass production is scheduled to begin this summer and reach a volume of 200,000 units per month by September 2017.
• Renesas has bought California chip company Intersil for $3.2bn.