Level triggered interrupt, edge triggered interrupt, comparison, hardware system, interrupt types

What are Level Triggered Interrupts and Edge Triggered Interrupts?

Level triggered interrupts and edge triggered interrupts are two types of interrupts used in embedded systems. An interrupt is a signal sent to the CPU, informing it that an event has occurred which needs to be handled. Level triggered interrupts and edge triggered interrupts differ in how they notify the CPU about the event.

Level Triggered Interrupts

Level triggered interrupts maintain their active state for a period of time. This means that the CPU will be notified of the interrupt the moment it is sent, and the interrupt must remain active until the CPU signals that it was handled. The active state of the interrupt can be maintained through circuitry or by setting a specific memory address to a known value. Examples of devices that use level triggered interrupts include timer, serial port and keyboard controllers.

Edge Triggered Interrupts

Edge triggered interrupts only send a signal to the CPU when the triggering event occurs. This means that the interrupt will not be resent again while the CPU is handling it. It is possible to create a level triggered interrupt out of an edge triggered one by storing the trigger state in memory, but this is not as efficient compared to using a dedicated level triggered interrupt. Examples of devices that use edge triggered interrupts include keyboard and mouse controllers.

Difference Between Level Triggered Interrupts and Edge Triggered Interrupts

• Level Triggered Interrupts: Level triggered interrupts maintain their active state for a period of time, meaning that the CPU is notified of the interrupt the moment it is sent.
• Edge Triggered Interrupts: Edge triggered interrupts only send a signal to the CPU when the triggering event occurs, and the interrupt will not be resent again while the CPU is handling it.