SafeLS: An Open Source Implementation of a Lockstep NOEL-V RISC-V Core

Microcontrollers running safety-critical applications with high integrity requirements must provide appropriate safety measures to manage random hardware faults. For instance, automotive safety regulations (e.g., ISO26262) impose the use of diverse redundancy for items at the highest automotive safety integrity level (ASIL), ASIL-D. In the case of computing cores, this is realized with dual core lockstep (DCLS). The advent of the RISC-VISA has made open source hardware gain popularity. However, there are few industrial open source SoCs meeting the requirements of safety-critical systems, and, to our knowledge, none of them provides lockstep cores. This paper presents the realization of a RISC-V open source lockstep core based on Gaisler's NOEL-V core for the space domain, as well as its integration in the SELENE SoC that provides a complete microcontroller synthesizable on FPGA successfully assessed against space, automotive and railway safety-critical applications in the past.