๐๐ก๐๐ญ ๐ข๐ฌ ๐๐ง ๐๐ง๐ญ๐๐ซ๐ซ๐ฎ๐ฉ๐ญ?
At its core, an interrupt is a signal to the processor of an event that requires immediate attention. Imagine reading a book and suddenly your phone rings. You stop reading, answer the phone, and after finishing the call, you resume reading from where you left off. In this analogy, the phone call is an interrupt to your reading activity.
In computer terms, an interrupt alerts the CPU to pause its current task and address the new task related to the interrupt. Common sources of interrupts include Input/Output (I/O) activities, timers reaching their limit, or even error occurrences like trying to divide by zero.
๐๐ก๐ฒ ๐๐ซ๐ ๐๐ง๐ญ๐๐ซ๐ซ๐ฎ๐ฉ๐ญ๐ฌ ๐๐ฆ๐ฉ๐จ๐ซ๐ญ๐๐ง๐ญ?
Efficiency: Instead of the CPU constantly checking the status of devices (known as “polling”), interrupts allow the CPU to work on other tasks until a device signals it needs attention.
Error Handling: Interrupts provide a mechanism for the system to handle unexpected events or errors in a controlled manner.
Routine Reminders: They can remind the CPU to perform routine tasks at regular intervals.
๐๐ง๐ญ๐๐ซ๐ซ๐ฎ๐ฉ๐ญ ๐๐๐ฌ๐ค๐๐๐ข๐ฅ๐ข๐ญ๐ฒ:
Maskable Interrupts: These are the interrupts that the CPU can choose to ignore. Before they can interrupt the CPU, they must be enabled, typically by setting a flag.
Non-maskable Interrupts: These are critical interrupts that the CPU cannot ignore, often representing urgent system events.
๐๐ง๐ญ๐๐ซ๐ซ๐ฎ๐ฉ๐ญ ๐๐ซ๐ข๐จ๐ซ๐ข๐ญ๐ฒ:
In scenarios where multiple interrupts occur simultaneously, a priority system determines which interrupt should be serviced first.
๐๐๐ซ๐ฏ๐ข๐๐ข๐ง๐ ๐๐ง ๐๐ง๐ญ๐๐ซ๐ซ๐ฎ๐ฉ๐ญ:
When an interrupt occurs, the CPU follows a sequence of steps:
1. Save the current state of the program, including the program counter and CPU status.
2. Determine the cause of the interrupt.
3. Locate the starting address of the appropriate Interrupt Service Routine (ISR) to handle the interrupt.
4. Execute the ISR.
5. Restore the saved state of the program and resume execution.
๐๐ง๐ญ๐๐ซ๐ซ๐ฎ๐ฉ๐ญ ๐๐๐๐ญ๐จ๐ซ & ๐๐๐๐ญ๐จ๐ซ ๐๐๐๐ฅ๐:
The “Interrupt Vector” is the address of the ISR. All these vectors are stored in a table known as the “Interrupt Vector Table”. The method to determine these vectors varies across different microcontrollers and architectures.
๐๐ซ๐จ๐ ๐ซ๐๐ฆ๐ฆ๐ข๐ง๐ ๐ฐ๐ข๐ญ๐ก ๐๐ง๐ญ๐๐ซ๐ซ๐ฎ๐ฉ๐ญ๐ฌ:
1. Initialize the Interrupt Vector Table.
2. Write the Interrupt Service Routine to address the interrupt’s cause.
3. Enable the interrupt so that the CPU can recognize it.
๐๐ง๐ญ๐๐ซ๐ซ๐ฎ๐ฉ๐ญ ๐๐ฏ๐๐ซ๐ก๐๐๐:
Handling an interrupt isn’t free; there’s an “overhead” or cost associated with it:
– Time taken to save and restore CPU status.
– Execution time of the ISR.
– Time for restoring the CPU state and resuming the main program.
Interrupts are crucial in embedded systems, allowing for efficient multitasking, timely responses to external events, and effective error handling. However, it’s essential to manage them effectively to ensure the system’s responsiveness and reliability.
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An Article by: Yashwanth Naidu Tikkisetty
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