Nios® II Processor Reference Guide

ID 683836
Date 10/22/2020
Public
Document Table of Contents

3.7.13.2. Masking Interrupts with an External Interrupt Controller

Typical EIC implementations allow system software to mask individual interrupts. The method of masking individual interrupts is implementation-specific.

The status.IL field controls what level of external maskable interrupts can be serviced. The processor services a maskable interrupt only if its requested interrupt level is greater than status.IL.

An ISR can make run-time adjustments to interrupt nesting by manipulating status.IL. For example, if an ISR is running at level 5, to temporarily allow pre-emption by another level 5 interrupt, it can set status.IL to 4.

To enable all external interrupts, set status.IL to 0. To disable all external interrupts, set status.IL to 63.

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