Nios II Classic Software Developer’s Handbook

ID 683282
Date 5/14/2015
Public
Document Table of Contents

8.3.1.5. Keep Interrupts Enabled

When interrupts are disabled, the Nios II processor cannot respond quickly to hardware interrupt events. Buffers and queues can fill or overflow. Even in the absence of overflow, maximum interrupt processing time can increase after interrupts are re-enabled, because the ISRs must process data backlogs.

Disable interrupts as infrequently as possible, and for the briefest time possible.

Instead of disabling all interrupts, call alt_ic_irq_disable() and alt_ic_irq_enable() to enable and disable individual interrupts.

To protect shared data structures, use RTOS structures such as semaphores.

Disable all interrupts only during critical system operations. In the code where interrupts are disabled, perform only the bare minimum of critical operations, and reenable interrupts immediately.