Introduction of Microprocessor, Microcomputer, Microcontroller

An overview of Microprocessor 

The first question that comes in one’s mind is "What is a microprocessor?”. Let us start with a more familiar term computer. A digital computer is an electronic machine capable of quickly performing a wide variety of tasks. They can be used to compile, correlate, sort, merge and store data as well as perform complex calculations at much faster rate than human beings by means of stored instructions.

A digital computer is different from a general-purpose calculator in a sense that digital computer is capable of operating according to the instructions that are stored within the computer whereas a calculator must be given instructions on a step by step basis to perform calculations. By this definition, a programmable calculator can be considered a computer.

Historically, digital computers have been categorized according to the size using the words large, medium, minicomputer, and microcomputer. In the early years of development, the emphasis was on large and more powerful computers. Large and medium-sized computers were designed to solve complex scientific and engineering problems. In early stage of development, these computers were accessible and afformidable only to large corporations, big universities, and government agencies. Later on, minicomputers were made available for use in offices, small collage, medium-size business organizations, small factory, etc. As the technology has advanced from SSI to VLSI & SLSI, the face of the computer has changed gradually and it became possible to build the entire central processing unit (CPU) on a single-chip known as microprocessor. 

A control processing unit (CPU) with its related timing functions on a single chip known as microprocessor. A microprocessor combined with memory and input/output devices forms a microcomputer.

The microcomputer is making an impact on every activity of mankind. It is being used in almost all control applications. For example analytical and scientific instruments, data communication, character recognition, musical instruments, household items, defence equipments, medical equipment, etc.

Microcomputers or, in general, computers communicate and operate in binary numbers ‘0’ and ‘1’ also known as bits. A bit is the abbreviation for the term binary digit. The bit size of a microprocessor refers to the number of bits which can be processed simultaneously by the arithmetic circuit of the microprocessor. A number of bits taken as a group in this manner is called word. For example, the first commercial microprocessor the Intel 4004 which was introduced in 1971 is a 4-bit machine and is said to process a 4-bit word. A 4-bit word is commonly known as nibble and an 8-bit word is commonly known as byte. Intel 8085A is an 8-bit microprocessor whereas Intel 8086 is a 16-bit microprocessor. It should be noted that a processor can perform calculations involving more than its bit size but through program and takes more time to complete the operation. For example, multi-byte data can be added byte by byte in 8085A processor which is an 8-bit processor. The short word length requires few circuitry and interconnection in the CPU.

MicroComputers

In a very general sense, a microcomputer is best regarded as a system incorporating a CPU and associated hardware whose purpose is to manipulate data in some fashion. This is exactly what any digital circuit designed using SSI’s and MSI’s does. Therefore, microcomputer should be regard as a general-purpose logic device. In contrast to standard SSI’s and MSI’s where the manufacturer decides what the device will do, with microcomputer it is the user who decides what the device should do by asking it to execute a proper set of instructions. A microcomputer, from this point of view is merely an assembly of devices whose sole task is to ensure that the instruction desired are indeed carried out properly and to allow the microprocessor to communicate with the real world, i.e. the user environment. The power of the microcomputer lies in the fact that if the application changes, the same system can be used by appropriately modifying the instructions to be executed and, if necessary, some changes in the hardware. In contrast, a digit circuit designed using SSI’s and MSI’s for some application will need to be completely redesigned if the application changes significantly

The objective of a microcomputer (μc) is to manipulate data in a certain fashion specified by the system designer. A typical microcomputer achieves their objective by getting its CPU to execute a number of instructions in the proper sequence. This sequence of instruction comprises the program that is executed by the microcomputer. A microcomputer which does nothing other than manipulate data present within itself, will not be of much use to anyone. In order to do something meaningful, data being manipulated should depend on inputs provided to the microprocessor by the user. Similarly, the data manipulations being carried out by the microprocessor would be completely meaningless unless the results of these manipulations affect things outside the microcomputer itself. Therefore, the µc should provide outputs which in some way depend on its inputs, the way inputs and outputs are related is decided by the program that gets executed.

Therefore, a microcomputer is an assembly of devices including a CPU, which manipulate data depending on one or more inputs and according to a program, in order to generate one or more output.

MicroControllers

A µP does not have enough memory for program and data storage, neither does it has any input and output devices. Thus when a µP is used to design a system, several other chips, such as memory chips and input/output ports, are also used to make up a complete microcomputer system. For many applications, these extra chips imply additional cost and increased size of the product and may not be suitable for the application. For example, when used inside a toy, a designer would like to minimize the size and cost of the electronic equipment inside the toy. Therefore, in such applications a microcontroller is used more often than a microprocessor.

A microcontroller is a chip consisting of a microprocessor, memory and input/output ports. 

Applications of Microprocessors:

The application of microprocessors is increasing day by day. Some of the applications are: 

• Analytical scientific instruments 
• Smart terminals 
• Stacker crane controls
• Conveyor controls
• Word processor
• Point of scale systems
• Standalone electronics cash system
• Electronic games
• Vending and dispensing machines
• Market scales
• Traffic light controls
• Home heating and lighting controls
• Security & fire alarm system
• Home appliances
• Computer-aided instruction
• Online control of lab instrumentation 
• Desktop computers
• Check processor
• Payroll system
• Inventory control
• Automatic type setting
• Compact business machines
• Medical instrumentation
• Automobile diagnostics
• Data communication processing
• Optical character recognition
• I/O terminal for computers.