Interrupts

• Interrupt-request line

o   Interrupt-acknowledge signal

o   Interrupt-request signal

• Interrupt-service routine

o   May have no relationship to program being executed at time of interrupt

o   Similar to subroutine

• Interrupt latency
• Program info must be saved

Transfer of control through the use of interrupts

Interrupts

Examples of the interrupts:

•   I/O device request, OS call, page fault
•   power failing, arithmetic overflow
•   Invalid opcode, breakpoint, protection violation

Interrupts (aka faults, exceptions, traps) frequently require

•   connecting return address
•   surprise jump (to vectored address)
•   state change ( for example, to kernel mode)
•   saving of PSW (including CCs)