ABSTRACT
The microprocessor central processing unit (CPU) forms the heart of any microprocessor or microcomputer system computer and, consequently, its operation is crucial to the entire system.The primary function of the microprocessor is that of fetching, decoding and executing instructions resident in memory.As such, it must be able to transfer data from external memory into its own internal registers and vice versa. Furthermore, it must operate predictably, distinguishing, for example, between an operation contained within an instruction and any accompanying addresses of read/write memory locations. In addition, various system housekeeping tasks need to be performed, including being able to suspend normal processing in order to respond to an external device that needs attention.
