Polled interrupt definition
A polled interrupt is a type of software interrupt – a technique that computers use to check whether their connected devices need anything. Instead of waiting for the devices to signal they need help, the computer regularly asks them if they need attention. For example, it may check if a key has been pressed on the keyboard, if there's a new document to print, or if a sensor has new data to process. The opposite of a polled interrupt is a vectored interrupt, where the device sends a signal to the computer to get its attention immediately.
See also: software interrupt
How a polled interrupt works
- The computer or microcontroller starts a loop to regularly check the status of connected devices.
- In each loop, the computer asks each device (such as a keyboard, printer, or sensor) if it needs any action.
- The computer looks at the device's response. If the device needs something (like playing a new song on a music player or recording a key press), the computer handles that task.
- The computer continues the loop, repeatedly checking each device at regular intervals.
Polled interrupt pros and cons
Let’s look at the pros and cons of a polled interrupt.
Pros
- Easy to implement and understand.
- Checks devices at regular, predictable intervals.
- Simplifies system design.
- Provides full control over how often devices are checked.
- Ideal for systems with few device interactions.
Cons
- Wastes processing power by checking devices unnecessarily.
- It’s slower at responding to devices because checks are not constant.
- Becomes less efficient with more devices.
- Not great for real-time tasks because of possible delays.
