In this paper, a microprocessor will be viewed as a stand-alone, self-contained single-chip microcomputer. For this to apply, it must have a central processing unit (CPU), nonvolatile and program memory, and input and output capabilities. A structure that has these can be programmed in some convenient programming language and can interact with the outside world through the input/output (I/O) ports. But there are other less obvious requirements. Clearly, for a self-contained system, the microprocessor must be relatively simple, reasonably small, and hence limited in most of its features-memory, processing power and speed, addressing range, and of course, the number of I/O devices it can interact with. Unlike computers, the designer must have access to most features of the microprocessor - the bus, memory, registers, and all I/O ports. In short, the microprocessor is a mere component with flexible features that the engineer can configure and program to perform a task or a series of tasks. The limits on these tasks are only two: the objective limitations of the microprocessor and the imagination (or capabilities) of the designer. For the purpose of this discussion, it is narrowed down to 8-bit microprocessors since these are some of the simplest and are commonly used in sensor/actuator systems, and because they are representatives of all microprocessors (16and 32-bit microprocessors are also in common use, but the principles involved in interfacing are essentially the same). Even within these there are a number of architectures being used.
Interfacing to Microprocessors, Page 1 of 2
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