For latest version of Nuclei ISA Spec since 2022, please get it from AE of Nuclei System Technology. This online version is out of date.
This document describes the ISA (Instruction Set Architecture) implemented in Nuclei processor core, including the instruction set and privileged architecture features.
Basically, Nuclei processor core are following and compatible to RISC-V standard architecture, but there might be some additions and enhancements to the original standard spec.
To respect the RISC-V standard, this document may not repeat the contents of original RISC-V standard, but will highlight the additions and enhancements of Nuclei defined.