STMicroelectronics AN1776 Interrupt Handling for STR7 Microcontrollers

About this manual

This document provides a description of using the Enhanced Interrupt Controller (EIC) on STR7 microcontrollers to handle IRQ and FIQ exceptions. It details how to configure the controller to meet specific application requirements.

The guide covers fundamental concepts such as exception entry and exit mechanisms, priority levels for various interrupts, and vector table configuration. It also includes examples of interrupt handling in C code and explains the differences between using standard assembly versus compiler-specific keywords like __irq.

What's inside

• Exception Entry and Exit
• Exception Priorities
• Exception Vectors
• ARM or Thumb State
• IRQ vs FIQ Interrupts
• Simple Interrupt Handling in C
• Interrupt Handling Using the EIC
• EIC Overview

Specifications

Frequently asked questions

What is the priority order of exceptions in STR7 microcontrollers?

The highest priority is Reset, followed by Data Abort, FIQ (Fast), IRQ (Normal), Prefetch Abort, SWI, and finally Undefined instruction.

Can exception handlers be written in Thumb instructions?

Yes, but any exception handler code written with the Thumb instruction set will return the processor to ARM state because the program counter must go back to the original application code which uses ARM instructions.

How does the EIC manage peripheral interrupts?

The Enhanced Interrupt Controller handles multiple interrupt channels, priority levels, and automatic vectorization when a peripheral generates an IRQ line.