Nios® II Processor Reference Guide

ID 683836
Date 8/28/2023
Document Table of Contents

3.9.10. Potential Unimplemented Instructions

Some Nios® II processor cores do not support all instructions in hardware. In this case, the processor generates an exception after issuing an unimplemented instruction. Only the following instructions can generate an unimplemented instruction exception:
  • mul
  • muli
  • mulxss
  • mulxsu
  • mulxuu
  • div
  • divu
  • initda

All other instructions are guaranteed not to generate an unimplemented instruction exception.

An exception routine must exercise caution if it uses these instructions, because they could generate another exception before the previous exception is properly handled.

Refer to the "Unimplemented Instruction" section of this chapter for more information regarding unimplemented instruction processing.