INTERRUPTSIt is an unexpected hardware initiated subroutine call orjump that temporarily suspends the running of thecurrent program.Interrupt is a process where an external device can getthe attention of the microprocessor. Initiation of I/O operation. Completion of I/O operation.An interrupt may be either: Edge Sensitive Level Sensitive
CATEGORIES OF INTERRUPTSMaskable Interrupts.Non-Maskable Interrupts.Vectored Interrupts.Non-Vectored Interrupts.
TYPES OF INTERRUPTSExternal Interrupt.Internal Interrupt.Software Interrupt.Hardware Interrupt.
USES OF INTERRUPTSInput/Output data transfers for peripheraldevices.Emergency situations like power down.Input signals to be used for timing purposes.Event driven programs.Real time response applications and inmultitasking system.
INTERRUPT CONTROLLED I/O TRANSFERS It is an asynchronous mechanism. Each device is connected to an interrupt line. When it needs service, it asserts the interrupt line to request the processors attention. The status of being executed must first be saved & it will be saved on stack If one or more device is connected to the interrupt line, the processor ends to know which device service routine it should branch to. The identification of the device requesting service can be done in either hardware or software or a combination of both.
INTERRUPT CONTROLLED I/O TRANSFERS Software Determination of the Requesting Device. Enable Interrupts. Request an Interrupt. Servicing the Interrupt. Returning to main program. Interrupt Latency & Interrupt Response Time. Interrupt Latency. Interrupt Response Time.
INTERRUPT CYCLEIn this cycle, CPU has to check for an interrupteach time an instruction is executed.The interrupt enable flip-flop IEN can be set &cleared with two instructions namely ION & IOF. ION: Interrupts Enable On. IOF: Interrupts Enable Off.When IEN=0, Flag can’t interrupt computer.When IEN=1,Flag can interrupt computer.