Microprocessors vs Microcontrollers

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CMSC 391 -- Programming Microcontrollers

Microprocessors vs Microcontrollers

Microcontrollers

A microprocess is a general-purpose digital computer central processing unit. To make a complete micorcomputer, you add memory (ROM and RAM) memory decoders, an oscillator, and a number of I/O devices. The prime use of a microprocessor is to read data, perform extensive calcualtions on that data, and store the results in a mass storage device or display the results. The design of the microcontroller is driven by the desire to make it as expandable and flexible as possible.

Microcontrollers

A microcontroller is a true computer on a chip. The design incorporates all of the features found in a micro-processor CPU: ALU, PC, SP, and registers. It also has ROM, RAM, parallel I/O, serial I/O, counters and a clock circuit. The microcontroller is a general-purpose device meant to read data, perform limited calculations on that data and control its environment based on those calcualtions. The prime use of a microcontroller is to control the oeprations of a machine using a fixed program that is stored in ROM and does not change over the lifetime of the system. The miccontroller 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.

Summary

The contrast between a microcontroller and a microprocessor is best exemplified by the fact that most microprocessors have many operation codes (opcodes) for moving data from external memory to the CPU; microcontrollers may have one or two. Microprecssors may have one or two types of bit-handling instructions; microcontrollers will have many.

8051 programs are more compact and will run faster (than a microprocessor) to accomplish the similar tasks. The disadvantage of using a lean instruction set is increased programmer effort (expense) to write code; this disadvantage can be overcome when writing large programs by the use of high-level languages such as BASIC and C, both of them are popular with 8051 system developers. The price paid for reducing programmer time (and there is always a price) is the size of the program generated (which could drive up the unit cost of the system.)

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