Laitteistokutsut

Laitteistokutsut, often translated as hardware invitations or hardware calls, refer to a communication method within certain computer systems where hardware components can directly request the attention of the processor. This is a fundamental mechanism for managing interrupts and handling asynchronous events generated by peripheral devices.

When a hardware device, such as a network card, a disk controller, or a timer, needs to signal the processor that it requires attention, it generates an interrupt. This interrupt is sent through a dedicated interrupt controller, which then signals the processor. The processor, upon receiving this signal, suspends its current task and initiates a process to identify the source of the interrupt.

This identification process involves a lookup mechanism, often using an interrupt vector table. Each interrupt request (IRQ) line is assigned a unique number, and this number corresponds to an entry in the interrupt vector table. This entry contains the memory address of the interrupt service routine (ISR) that is specifically designed to handle that particular hardware event. The processor then jumps to the address of the appropriate ISR, which executes the necessary code to service the hardware request, such as reading data from a buffer or acknowledging a completed operation.

Once the ISR has completed its task, it typically signals the interrupt controller that the interrupt has been serviced. The interrupt controller then allows the processor to resume its suspended task, often restoring the processor's state to what it was before the interrupt occurred. Laitteistokutsut are crucial for efficient multitasking and responsiveness in operating systems, allowing the system to react to external events without constantly polling devices for their status.