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Interrupts provide a way to you manage events without the need to polling status of external inputs.
Take in mind that polling consumes program processing.
However, in order to suport the interruption feature, core of microprontroller must include additional microinstructions, wich decreases a little the overall MIPS capability.
But not sure if we can consider it like a disvantage.
you have two options either use polling or interrupts.
polling means CPU have to check every time the status of the device.
Interrupts means interruption in the sequential flow of the program.actually the processor is too faster than your hardware and can perform more task in the same time as the hardware fetches the data to it. so most of the time interrupts are used.
whenever a device needs the attention of the CPU it generates a signal. the processor finishes the current task before responding to the device(it also saves the current status example save program location in PC register). the CPU then accepts the interrupt (in case of priority based interrupts check the priorty), and the transfers the control to the interrupt routine.
Interrupts are used when you need the fastest response to an event.
disadvatge of priority based interrupts is that faster devices have to wait for slower devices.