The interest of the space industry around soft processors is increasing. However, the advantages in terms of costs and customizability provided by soft processors are countered by the reliability issues deriving by Single Event Effects, especially Single Event Upsets. Several techniques have been proposed to tackle these issues, both at the hardware- and software levels. Software approaches rely on replicating data and computations to cope with SEUs affecting the memory where the binary code is stored. Thanks to open licenses, RISC-V solutions are steadily growing in popularity among the set of available soft processors. In this works, we present a reliability evaluation of four different benchmarks running on the RI5CY soft processor implemented on SRAM-based FPGAs. The reliability of the baseline and hardened-by-replication versions of the software benchmarks are evaluated against SEUs-induced faults both at the software and hardware architecture levels through fault injection campaigns in the microprocessor memory and configuration memory, respectively. Results assess how the adoption of the hardening-by-replication technique at the software level slightly improves reliability against software-related faults but degrades reliability against architectural faults, making it an inefficient solution when it is not combined with hardware robustness.

Single event transients (SETs) have become increasingly problematic for modern CMOS circuits due to the continuous scaling of feature sizes and higher operating frequencies. Especially when involving safety-critical or radiation-exposed applications, the circuits must be designed using hardening techniques. In this brief, we present a new radiation-hardened-by-design full-adder cell on 45-nm technology. The proposed design is hardened against transient errors by selective duplication of sensitive transistors based on a comprehensive radiation-sensitivity analysis. Experimental results show a 62% reduction in the SET sensitivity of the proposed design with respect to the unhardened one. Moreover, the proposed hardening technique leads to improvement in performance and power overhead and zero area overhead with respect to the state-of-the-art techniques applied to the unhardened full-adder cell.

The continuous scaling of electronic components has led to the development of high-performance microprocessors which are even suitable for safety-critical applications where radiation-induced errors, such as single event effects (SEEs), are one of the most important reliability issues. This work focuses on the development of a fault injection environment capable of analyzing the impact of errors on the functionality of an ARM Cortex-A9 microprocessor embedded within a Zynq-7000 AP-SoC, considering different fault models affecting both the system memory and register resources of the embedded processor. We developed a novel Python-based fault injection platform for the emulation of radiation-induced faults within the AP-SoC hardware resources during the execution of software applications. The fault injection approach is not intrusive, and it does not require modifying the software application under evaluation. The experimental analyses have been performed on a subset of the MiBench benchmark software suite. Fault injection results demonstrate the capability of the developed method and the possibility of evaluating various sets of fault models.

The continuous scaling of electronic components has led to the development of high-performance microprocessors that are suitable even for safety-critical applications where radiation-induced errors such as Single Event Effects (SEEs) can have a significant impact on the performance and reliability of the system. This work is dedicated to investigating the reliability of systems based on programmable hardware and Real-time operating Systems (RTOS) in the presence of architectural faults induced by soft errors in the configuration memory of the programmable hardware. We performed a proton radiation test campaigned at PSI radiation facility to identify the fault model affecting the configuration memory of Xilinx Zynq-7020 reconfigurable AP-Soc Device. The identified fault model in terms of SEU and MBU clusters has been used to evaluate the impact of proton-induced faults on applications running within FreeRTOS on a Microblaze soft processor. A Single Event Multiple Upset fault model resulting from a proton test is presented, focusing on characteristics such as shape, size, and frequency of observed cluster of errors. We conduct two fault injection campaigns and analyze the results to assess the effect of cluster size on system reliability. Moreover, we discuss software exceptions caused by faults that can affect the hardware structure of the soft processor.