Abstract

Microcontrollers are not as well known to the general public, or to many in the technical community. Microcontrollers and Microprocessors stem from the same basic idea that are made by the same people and are sold to the same type of system designers and programmers. Microprocessor is a general purpose digital computer central processing unit (CPU). But the Microcontroller is a true computer on a chip, that is, a single chip computer.

Microcontroller is a general purpose device, but one that is meant to read data, perform limited calculations. That is, because the amount of memory and interfaces that can fit on a single chip is limited, microcontrollers tend to be used in smaller systems that require little more than the microcontroller and a few support components. The prime use of the microcontroller is to control the operation of a fixed program that is stored, in ROM and that does not change over the lifetime of the system.

A Microcontroller is similar to the microprocessor inside a personal computer. Examples of microprocessors include Intel's 8086, Motorola's 68000, and Zilog's Z80, AT89C51. Micro suggests that the device might be used to control objects, processors, or events. Another term to describe a microcontroller is 'embedded controller', because the microcontroller and its support circuits are often built into, or embedded in, the devices they control.

These microprocessors and microcontroller contain a processing unit, or CPU. The CPU executes instructions that perform the basic logic, math, and data moving functions of a computer. That is, the design of the microcontroller incorporates all of the features found in microprocessor CPU: ALU, SP, PC and registers. To make a complete computer, a microprocessor requires memory for storing data and programs (ROM and RAM), input/output (I/O) interfaces for connecting external devices like keyboards and displays, parallel I/O, serial I/O counters, and a clock circuit; as additional features.
The microcontroller design uses a much more limited set of single and double byte instructions that are used to move code and data from internal memory to the ALU.

Many instructions that are coupled with on the integrated circuit package, the pins are 'programmable' ie, capable of having several different functions depending on the wishes of a programmer. The microcontroller is concerned with getting data from and to its own pins; the architecture and instruction set are optimized to handle data in bit and byte size.

Microcontroller will have many types of bit handling instructions. Microcontrollers may have one or two operational codes for moving data from internal memory to the CPU. They are concerned with rapid movement of bits within the chip. The microcontroller can function as a computer with the addition of no external digital parts.

Microcontroller models vary in the data size from 4 to 32 bits. Four bit units are produced in huge volumes for very simple applications and 8-bit units are the most versatile, 16 and 32 bit units are used in high speed control and signal processing applications. Many model feature programmable pins that allows external memory to be added with the loss of I/O capability

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