University of Twente Student Theses


Radiation resilience evaluation of a Flash-based FPGA with a soft RISC-V Core

Böhmer, Kevin (2023) Radiation resilience evaluation of a Flash-based FPGA with a soft RISC-V Core.

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Abstract:Highly reliable and customizable micro-processors are critical enablers for future intelligent space platforms. From an architectural point of view, the RISC-V architecture is the current best option for adaptability, with its modular ISA and a multitude of contributors. To implement such a processor at a low price range, companies are looking at reprogrammable Field-Programmable Gate Arrays~(FPGAs), which can extend the mission lifetime. SRAM FPGAs are known to be susceptible to low Linear Energy Transfer Single-Event Upsets~(SEUs) in the configuration memory, Flash FPGAs on the other hand, are in general immune to such errors. This thesis performs for the first time characterization of the open-core NEORV32, a lightweight yet representative RISC-V SoC, and provides insights into the tradeoffs of protection mechanisms against neutron-induced SEUs when this core is implemented in a Flash-based FPGA. The Unmodified core is compared against an ECC-protected version and a register-level Triple Modular Redundancy (TMR) with an Error Correction Code (ECC) version. All versions execute the CoreMark benchmark. The Unmodified NEORV32 instances mainly experienced exceptions arising from Single Event Upsets (SEUs) that affected stored pointers in the data memory. These altered pointers, when employed as addresses, resulted in Load and Store exceptions, stemming from the pointers now residing outside the valid memory range. The incorporation of ECC swiftly mitigated these disparities and reduced Store and Load exceptions to zero. Introducing TMR on the Flip-Flop level further advanced the outcome by eliminating all exceptions, including those tied to Illegal instructions. These Illegal instructions are likely the fallout of SEUs influencing control logic, culminating in Single-Event Functional Interrupts (SEFIs).
Item Type:Essay (Master)
Faculty:EEMCS: Electrical Engineering, Mathematics and Computer Science
Subject:50 technical science in general, 53 electrotechnology, 54 computer science
Programme:Embedded Systems MSc (60331)
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