External interruption in a computer system is caused by external influences, such as the user, peripheral devices, hardware devices, or a network. These interruptions come from input-output devices, a timer, a power supply monitor circuit, or any other external source. Interrupts can be classified into three categories: internal, software, and external. Interrupts are essential in microcontrollers and signal an event that requires immediate attention from the processor. A basic interrupt mechanism simplifies embedding software into hardware, especially as an application involves multiple modules.
What are External Interrupts?
An external interruption, as the name suggests, is an interruption caused by external influences such as peripherals, hardware devices, network, or user input on a computer system. These are usually categorized under input-output (l/0) devices, circuit monitoring power supply, timers, or any other external source affecting system performance.
Types of Interrupts
There are three main types of interrupts: internal, software, and external interrupts.
Internal interrupts occur when a program violates any of the CPU’s instructions or limitations, such as accessing not allowed operations or exceeding memory limits.
Software interrupts occur when a program runs an instruction intended to trigger an interrupt, such as system calls, which are used to request services from the operating system.
External interrupts, as previously mentioned, are caused by external factors such as user input, peripherals, and network.
Importance of Interrupt Mechanism
The interrupt mechanism plays a vital role in microcontroller programming. Interrupts are signals that indicate immediate system attention is required, triggered by hardware or software. As code gets more complex and applications involve multiple modules, sequential coding becomes too complex and lengthy. The interrupt mechanism provides an easier and more efficient way to embed software into the hardware.
Implementing Basic Interrupt Mechanism
Implementing a basic interrupt mechanism requires the following steps:
1. Set Up Interrupts: Before using interrupts, the handler function must be registered with the microcontroller’s interrupt service routine. The interrupt register is initially set as inactive.
2. Enable Interrupts: Once the interrupt function is set up, the corresponding interrupt must be enabled to allow it to work. Enabling interrupts ensures that the processor remains responsive to incoming interrupt signals.
3. Wait for Interrupt: The processor waits for an interrupt signal to occur. Once it happens, the microcontroller diverts its attention to the handler function.
4. Execute Interrupt Handler Function: The handler function performs specific tasks related to the interrupt that has occurred. Once the tasks are finished, control is returned to the main program.
The interrupt mechanism is an essential function for microcontroller programming. External interrupts, in particular, play a crucial role in ensuring system responsiveness and smooth operation. By understanding the basics of interrupts and implementing a basic mechanism, programmers can ensure efficient and effective microcontroller programming.