- Aiming for application in cars, robots and other IoT devices -

Tokyo, September 7, 2015 - NEC Corporation (NEC; TSE: 6701) today announced the development of a new LSI design technology for rewriteable field programmable gate arrays (NB-FPGA) that applies NanoBridge metal atom migration-type switch technology (*). As part of this technology, NEC developed a new method to predict NB-FPGA performance (single delay and power consumption) before a circuit is programmed onto an NB-FPGA, allowing circuits to be corrected and optimized in a flexible manner.

"This technology shortens LSI design time to about one-tenth when compared to a prior NB-FPGA design tool, achieving design times at the same level as a commercially available FPGA. This will make a significant contribution to the practical utilization of NB-FPGAs," said Yuichi Nakamura, general manager, Green Platform Research Laboratories, NEC Corporation.

"Moreover, this technology will allow us to optimize the circuit design for NB-FPGAs with exceptionally high power-efficiency. NB-FPGAs are expected to be used in a wide variety of environments, including the application in IoT devices, such as automotive control units and robots, which demand high performance and reduced power consumption."

Main features of the new technology include the following:

1. A new tool for predicting the operating frequency of an NB-FPGA circuit
   Even when a circuit programmed on an NB-FPGA operates properly, its operating frequency may be lower than expected.

In order to accurately predict the operating frequency of a circuit programmed on an NB-FPGA, it is necessary to obtain the overall delay time of the entire circuit. This overall delay time is obtained by calculating, then adding, the signal delay of each basic circuit component. However, the character of the basic circuit component possibly has over one million variations after programming, which complicates calculations.

In order to address this issue, NEC developed a new calculation technique that accurately predicts signal delay in the overall circuit by classifying basic circuit components into just 45 kinds of "basic cells" and 28 kinds of "correction cells," then calculating overall signal delay time based on this low number of circuit components.

This enables the signal delay for NB-FPGA logic circuits to be accurately ascertained across a wide range of operating voltages and ambient temperatures.

The use of NEC's new design tool enables repeated verification and modification of the points on a circuit that are causing delays, which permits users to eliminate the points causing slow operating speeds prior to a circuit being programmed onto an NB-FPGA. This enables the production of logic circuits that facilitate high operating frequency.

1. Accurate prediction of NB-FPGA power consumption
   Through a simulation of static current (leakage current) using NanoBridge resistance values (values from actual measurements), NEC learned that the actual static current values could be recreated. Moreover, the use of the dynamic current derived from NEC's tool to predict operating frequencies mentioned above, as well as the use of the static current, made it possible to accurately predict overall power consumption of an NB-FPGA.

Since the change in NanoBridge resistance values due to temperature is extremely small, deterioration of operating frequencies at high temperatures is lower for an NB-FPGA, and the increase in static current is also kept to one-third when compared with a conventional FPGA using an SRAM-based switch.

Moving forward, NEC plans to use NB-FPGAs in applications such as motor control for robots through the NEDO Project, which is being pursued on a joint basis with the University of Tokyo.

Note: (*) NanoBridge® is a resistance-change type switch developed by NEC together with the National Institute for Materials Science. By controlling the creation or destruction of bridges formed by metal atoms in a solid electrolyte through the application of voltage, its resistance changes significantly, functioning as a wiring switch. The switch's resistance value is maintained even when the power supply is turned off, giving it non-volatility. Circuit non-volatility is an effective way to achieve reduced power consumption in ICT devices and systems. NanoBridge® is a registered trademark of NEC.