смотри IRQ
(IRQ) The name of an input found on many processors which causes the processor to suspend normal instruction execution temporarily and to start executing an interrupt handler routine. Such an input may be either "level sensitive" - the interrupt condition will persist as long as the input is active or "edge triggered" - an interrupt is signalled by a low-to-high or high-to-low transition on the input. Some processors have several interrupt request inputs allowing different priority interrupts.