How external interrupts work, what are the external interrupt methods, and why should external interrupts be used?
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How external interrupts work, what are the external interrupt methods, and why should external interrupts be used?

Posted Date: 2024-01-28

The working principle of external interrupt is a mechanism for microcontroller to respond to external events..

When an external event occurs, the interrupt system of the microcontroller will interrupt the program being executed by the CPU and instead handle the interrupt event. After processing is completed, the CPU will return to the interrupted program and continue execution. This process can be divided into the following steps:

  • interrupt request: The external device sends an interrupt signal to the microcontroller through the interrupt request line.
  • Interrupt recognition: The interrupt controller of the microcontroller identifies the interrupt signal and decides whether to respond based on the priority.
  • interrupt response: If the interrupt is responded to, the CPU will save the current program status and jump to the interrupt service routine.
  • Interrupt handling: Execute the interrupt service routine and handle external events.
  • interrupt return: After the processing is completed, restore the previously saved program state and continue executing the original program.

There are two main ways of external interrupt: level trigger and edge trigger.. Level triggering means that the interrupt is triggered when the level of the external interrupt pin meets certain conditions; edge triggering means that the interrupt is triggered when the level of the external interrupt pin jumps (from high to low or from low to high).

The reason for using external interrupts is toAllow the microcontroller to respond to external events in real time. In the absence of interrupts, the microcontroller may be in an infinite loop and unable to process external changes in time. Through external interrupts, the microcontroller can suspend the current task when necessary and switch to processing more urgent external events, thereby improving the real-time performance and flexibility of the system.

To sum up, external interrupt is an internal mechanism designed by the microcontroller to process external events in real time. It allows the microcontroller to suspend the current task when necessary, handle the external interrupt request, and then return to continue executing the original program. This method improves the working efficiency of the microcontroller and its ability to respond to external events.


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