Why Interrupt vector table in Embedded C? - Purpose & Use Cases

The Big Idea

What if your device could react instantly without wasting a single moment checking for events?

The Scenario

Imagine you have a device that needs to respond quickly when a button is pressed or a sensor triggers. Without an interrupt system, your program must constantly check (poll) every input to see if something happened.

This means your program wastes time checking things that might not have changed, and it can miss important events if it's busy doing something else.

The Problem

Polling every input manually is slow and inefficient. It uses up precious processing time and can cause delays in reacting to important events.

Also, writing code to check each event in the right order is complicated and error-prone, especially as the number of inputs grows.

The Solution

The interrupt vector table is like a smart map that tells the processor exactly where to go when an event happens.

Instead of checking all the time, the processor jumps directly to the right piece of code to handle the event immediately, making your program faster and more reliable.

Before vs After

✗ Before

while(1) {
  if(button_pressed()) {
    handle_button();
  }
  if(sensor_triggered()) {
    handle_sensor();
  }
}

✓ After

void (*interrupt_vector[])() = {handle_reset, handle_button, handle_sensor};
// Processor jumps to correct handler automatically on interrupt

What It Enables

This lets your device respond instantly to events without wasting time checking, making it efficient and responsive.

Real Life Example

Think of a microwave oven that must stop heating immediately when you open the door. The interrupt vector table helps the processor jump right to the door-open handler without delay.

Key Takeaways

Polling inputs wastes time and can miss events.

The interrupt vector table directs the processor to the right code instantly.

This makes embedded systems faster and more reliable.