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 responding to an external
device that needs attention.
