8051 Micro-Controller

Introduction to Micro-controllers

Microprocessors and micro-controllers are widely used in embedded system products. An embedded product uses a microprocessor (or micro-controller) to do one task and one task only. Whereas a micro-controller is used in an embedded system which perform a specific and a dedicated task, a microprocessor is used in systems which can perform multiple tasks wiz a computer. A printer is an example of embedded system since the processor inside it performs only one task; namely, getting the data and printing it. PC on the other hand can be used for any number of applications such as word processor, print server, bank teller terminal, video game player, network server, or internet terminal. PC generally uses an operating system and a number of applications and system software, an embedded system with micro-controller on the other hand uses application software.

Application of micro-controllers:

Embedded processors and micro-controllers these days are found in almost any electronic device. Some of the frequently found systems/devices using micro-controllers are:

Home Appliances and gadgets

Appliances, intercom, telephones, security systems, garage door openers, answering machines, fax machines, home computers, TVs, cable TV tuner, VCR, camcorder, remote controls, video games, cellular phones, musical instruments, sewing machines, lighting control, paging, camera, pinball machines, toys, exercise equipment

Office Applications

Telephones, computers, security systems, fax machines, microwave, copier, laser printer, color printer


Trip computer, engine control, air bag, ABS, instrumentation, security system, transmission control, entertainment, climate control, cellular phone, keyless entry

Others Areas: 

Environmental control(greenhouse, factory, home), Instrumentation, aerospace, and many more.

Difference between a microprocessor and micro-controller:

A micro controller is an integrated circuit, but unlike a microprocessor, is a chip with a processor and other support devices like program memory, data memory, I/O ports, serial communication interface etc integrated together. Some of the basic difference between a microprocessor and micro-controller are:

Is generally used in systems capable of doing multiple tasks like a Personnel computer.
Generally used for a specific task like in an embedded system(printer, fax, …).
Require an operating system and application software to operate
Generally require application software to perform the dedicated task.
micro processor has many support devices like Read only memory, Read-Write memory, Serial interface, Timer, Input/Output ports etc. All these support devices are interfaced to microprocessor via a system bus.
All the support devices like Read only memory, Read – Write memory, Timer, Serial interface, I/O ports are internal.

Figure 1.1 Microprocessor based system

Figure 1.2 Micro-controller based system

Microprocessor is a CPU on a chip
Micro-controller is a system- on-a-chip
Microprocessor purely depends on the external memory
For small application code can be stored in the internal program memory and internal registers and scratch pad area of memory can be used as RAM.

For large size application, external memory can be interfaced with it.

The use of external interfacing of memory and other i/o make the system for application of general purpose and where CPU performance is more important than the size, cost and power consumption.
The on-chip memory and other features make it more attractive in applications where size, cost and power consumption is critical than the CPU performance itself

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