![]() ![]() Hardware InterruptsĪ hardware interrupt is a condition related to the state of the hardware that may be signaled by an external hardware device, e.g., an interrupt request (IRQ) line on a PC, or detected by devices embedded in processor logic to communicate that the device needs attention from the operating system. These are classified as hardware interrupts or software interrupts, respectively. Interrupt signals may be issued in response to hardware or software events. The operating system has another little program called a scheduler that figures out which program to control next. The interrupt handler prioritizes the interrupts and saves them in a queue if more than one is waiting to be handled. Of course, the computer operates at speeds that make it seem like all user tasks are being performed simultaneously.Īn operating system usually has some code that is called an interrupt handler. It allows the user to do many different things simultaneously, and the computer turns to manage the programs that the user starts. But, because it can be interrupted, it can manage how programs or sets of instructions will be performed. This is called Interrupt Latency.Ī single computer can perform only one computer instruction at a time. Also, saving the registers so that the interrupted process can be restored in the future increases the delay between the time an interrupt is received and the start of the execution of the ISR. While the processor is handling the interrupts, it must inform the device that its request has been recognized to stop sending the interrupt request signal. Therefore, after handling the interrupt, the processor can continue with the process. ![]() Before loading the program counter with the address, the address of the interrupted instruction is moved to a temporary location. Then it loads the Program Counter (PC) with the address of the first instruction of the ISR. When a device raises an interrupt at the process, the processor first completes the execution of an instruction. In I/O devices, one of the bus control lines is dedicated for this purpose and is called the Interrupt Service Routine (ISR). It alerts the processor to a high-priority process requiring interruption of the current working process. An interrupt is a signal emitted by hardware or software when a process or an event needs immediate attention. ![]()
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