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Unformatted text preview: 15-115-1InterruptsInterrupt: (verb) the interruption of a CPUs normal processing. . .. . .using a mechanism provided for this purpose.Interrupt: (noun). . .. . .(1) an event that causes an interrupt. . .. . .(2) the interface and CPU hardware implementinga particular interruptlevel.An interrupt can be any of the following:Interruption by an external device.In class, this is what is meant byinterrupt.Interruption by attempted illegalinstruction or memory access.Also calledexceptions.Interruption by timerwithin computer.Interruption by execution of a special instruction.Also calledtraps.(Used for system calls.)In this set, external-device interrupt will be covered.15-1EE 4770 Lecture Transparency. Formatted 13:27, 23 December 1997 from lsli15.15-115-215-2External-Device InterruptsHardware & Software InvolvedExternal EventPossible eventsTemperature exceeding limit.Person pressing a button.Disk drive signaling that data is ready.Sensor, Conditioning Circuit, Etc.Converts event to a logic level.This was covered earlier in the semester.Computer Input, CalledInterrupt Request (IRQ)Usually several IRQs available.A single IRQ can be shared.Kernel Code CalledService RoutineAttends to routine matters.Kernel Code CalledHandlerCalled by service routine.Attends to cause of interrupt.15-2EE 4770 Lecture Transparency. Formatted 13:27, 23 December 1997 from lsli15.15-215-315-3Interrupt Steps, OverviewOverview of Interrupt ActivitiesEvent occurs.Detected by sensor.An IRQ asserted by conditioning-circuit output.WhenCPUallowsinterruption. . .. . .it finishes in-progress instructions. . .. . .prevents (masks) other interrupts. . .. . .and jumps to service routine.Service routine. . .. . .saves context. . .. . .determines source of interrupt. . .. . .and callshandlerfor interrupt source.Handler. . .. . .stops interrupt. . .. . .and carries out interrupt-specific activities.After the handler returns. . .. . .the service routine restores registers. . .. . .and any interrupted task resumed.15-3EE 4770 Lecture Transparency. Formatted 13:27, 23 December 1997 from lsli15.15-315-415-4Software InterruptsExceptionsThese are caused by illegal instructions, operands, and memory ac-cesses.The service routine can usually determine the reason for the exceptionby examining a register.The OS may stop the task or run a task-provided handler....
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This note was uploaded on 11/28/2011 for the course EE 4770 taught by Professor Staff during the Fall '99 term at LSU.
- Fall '99