Wednesday, December 2, 2009


Interrupt is the signal, which tends to jump the program from current executing location to specified program location, to do a specific task called Interrupt Service Routine(ISR). Interrupt is the most important concept in microcontrollers. On execution and completion of ISR, the programs returns to the location where, interrupt was arrived. The specified address where program jumps on arrival of an interrupt is called Interrupt Service Vector.

Interrupts can be categorized as: maskable interrupt, non-maskable interrupt, interprocessor interrupt (IPI), software interrupt.

A maskable interrupt(IRQ) is a hardware interrupt that may be ignored by setting a bit in an interrupt mask register's (IMR) bit-mask. As well the priority of the maskable interrupt can be configured.

A non-maskable interrupt (NMI) is a hardware interrupt can never be ignored. It is having the highest priority.

An interprocessor interrupt is a special case of interrupt that is generated by one processor to interrupt another processor in a multiprocessor system.

A software interrupt is an interrupt generated within a processor by executing an instruction. Software interrupts are often used to implement System calls because they implement a subroutine call with a CPU ring level change.

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