Handling the requests for interrupt

• The I/O device signals an event that requires immediate attention

• The I/O interface of such device raises an IRQ signal that reaches the Programmable Interrupt Controller (PIC) chip

• The PIC polls continuously the IRQ lines connected to it; when it detects a signal on one of them, it raises the INT line connected to the CPU chip

• If interrupts are not disabled, the CPU switches control to handle the interrupt