Nios II Classic Processor Reference Guide

ID 683620
Date 10/28/2016
Document Table of Contents Nested Exceptions with the Internal Interrupt Controller

You can enable nested exceptions in each exception handler on a case-by-case basis. If you want to allow a given exception handler to be pre-empted, set status.PIE to 1 near the beginning of the handler. Enabling maskable interrupts early in the handler minimizes the worst-case latency of any nested exceptions.
Note: Ensure that all pre-empting handlers preserve the register contents.