ABSTRACT
In this chapter, the author explains how computer systems use exceptions (including traps, hardware interrupts, etc.) to alert the processor to various conditions that may require its attention. An exception, in generic terms, can be any synchronous or asynchronous system event that occurs and requires the attention of the central processing unit (CPU) for its resolution. Exceptions caused by hardware devices (often input/output (I/O)devices) in a system are generally referred to as interrupts. The obvious origin of this term lies in the mechanism employed by external devices to get the attention of the CPU. Processors that are intended for use in embedded systems (inside some other piece of equipment) also generally have an alternate reset mechanism known as a watchdog timer. In contrast to systems using memory-mapped I/O, some architectures define a second address space to be occupied exclusively by I/O device interfaces.
