Interrupt Handling

Precise Interrupt

A precise interrupt maintains the state before the interrupt before handling the exception.

Any I/O device that requests attention uses a prioritised interrupt request line.

The interrupt handler saves the Exception Program Counter (EPC) to allow nested interrupts.

The status register indicates the cause of the interrupt.

A special jump instruction RFE (return from exception) is used to resume code. It * enables interrupts * returns the processor to the user mode * restores the hardware status and control state