Single event upset mitigation techniques in reconfigurable hardware

• Main Author: Vavouras, Michail
• Other Authors: Bouganis, Christos
• Published: Imperial College London 2017
• Subjects: 621.3
• Online Access: https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.726976

Advances in semiconductor technology using smaller sizes of transistors in order to fit more of them in the same area and increase performance, pose a threat for the reliability of integrated circuits. Technology scaling accelerates transistor ageing and degradation, causing more faults during the lifetime of an integrated circuit. Sources of faults such as manufacturing defects, degradation and ageing of transistors degrade the performance of integrated circuits leading to faults with a permanent effect that might be catastrophic for certain applications. A special case of integrated circuits, FPGAs, suffer from radiation-induced faults since they contain million of bits for the configuration of their resources that if flipped due to radiation might change the intended functionality of the application running on the FPGA, causing a failure. However, FPGAs can be dynamically reconfigured in the field and mitigate radiation effects providing fault-tolerance and high availability. A novel fault-tolerant architecture for an artificial pancreas application is proposed that consists of a mixed substrate of ASIC and FPGA. Fault detection is provided through modular redundancy, and dynamic reconfiguration is used as a repair mechanism. Experimental results show that 5,100x lower probability of failures per hour (PFH) than a DMR for permanent faults can be achieved with 2.4x more area than DMR. In addition, the proposed solution achieves 83x lower PFH than a TMR with 1.6x area overheads when considering transient faults. A framework supporting fault injection at the configuration memory of an SRAM FPGA and scrubbing was developed throughout this work. The framework supports various SEU and scrub rates and is implemented on the modern ZYNQ FPGA architecture. Existing scrubbing strategies were implemented for a second-order polynomial case study together with two new scrubbing techniques taking into consideration area information of the modules of the application. Experimental results show that the area-driven scrubbing technique achieves 43.6% LUTs and 40.9% REGs savings when compared to a DMR design. The area-driven technique for the partial TMR design saves 15% LUTs and 23% REGs area as compared to the TMR without sacrificing availability, but with increased power consumption for scrubbing. The conclusion of the work is that dynamic reconfiguration techniques can be effectively applied in FPGAs for trading-off resources and power consumption for availability.