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Microcontrollers : An Overview

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A microcontroller is a small and low-cost computer built for the purpose of dealing with specific tasks, such as displaying information in a microwave LED or receiving information from a television’s remote control. Microcontrollers are mainly used in products that require a degree of control to be exerted by the user.



An Image of 8051 Microcontroller

Fig. 1: An Image Of 8051 Microcontroller

Microcontroller v/s microprocessor 

Microprocessors are used to execute big and generic applications, while a microcontroller will only be used to execute a single task within one application. Some of the benefits of microcontrollers include the following: 
·         Cost advantage: The biggest advantage of microcontrollers against larger microprocessors is that the design and hardware costs are much lesser and can be kept to a minimum. A microcontroller is cheap to replace, while microprocessors are ten times more expensive.
·         Lesser power usage: Microcontrollers are generally built using a technology known as Complementary Metal Oxide Semiconductor (CMOS). This technology is a competent fabrication system that uses less power and is more immune to power spikes than other techniques.
·         All-in-one: A microcontroller usually comprises of a CPU, ROM, RAM and I/O ports, built within it to execute a single and dedicated task. On the other hand, a microprocessor generally does not have a RAM, ROM or IO pins and generally uses its pins as a bus to interface to peripherals such as RAM, ROM, serial ports, digital and analog IO. Read more about the difference between microcontroller and microprocessor.  
How does a Microcontroller work? 
Microcontroller has an input device in order to get the input and an output device (such as LED or LCD Display) to exhibit the final process. Let us look into the illustration of how a microcontroller works in a Television.
The Television has a remote control as an Input device and the TV screen as the output device. The signal sent from the remote control is captured by the microcontroller. The microcontroller controls the channel selection, the amplifier system and picture tube adjustments such as hue, brightness, contrast etc.
General architecture of a microcontroller 
The architecture of a microcontroller depends on the application it is built for. For example, some designs include usage of more than one RAM, ROM and I/O functionality integrated into the package.
General Architecture Of A Microcontroller
Fig. 2: General Architecture Of Microcontroller
The architecture of a typical microcontroller is complex and may include the following:
1.      A CPU, ranging from simple 4-bit to complex 64-bit processers.
2.      Peripherals such as timers, event counters and watchdog.
3.      RAM (volatile memory) for data storage. The data is stored in the form of registers, and the general-purpose registers store information that interacts with the arithmetic logical unit (ALU).
4.      ROM, EPROM, EEPROM or flash memory for program and operating parameter storage.
5.      Programming capabilities.
6.      Serial input/output such as serial ports.
7.      A clock generator for resonator, quartz timing crystal or RC circuit.
8.      Analog-to-digital convertors.
9.      Serial ports.
10. Data bus to carry information.

Features and Applications


Features of microcontrollers 

1.      Architectural features:
Most microcontrollers built today are based on the CISC (Complex Instruction Set Computer) platform. A typical CISC microcontroller has over 80 instructions and it is quite common for the instructions to all behave quite differently.
The main advantage of CISC architecture is that the instructions are macro-like, allowing the programmer to use one instruction in place of many simpler instructions.
2.     Advanced Memory features:
          a.    Electrically Erasable Programmable Read Only Memory (EEPROM):
Many microcontrollers use the economic EEPROM for smaller amount of memory that have frequently changeable data. This type of memory is relatively slow, and the number of erase/write cycles allowed in its lifetime is limited. 
          b.    FLASH (EPROM): 
Flash provides microcontrollers with a better solution than EEPROM for requirements of large amounts in non-volatile program memory. EPROM is faster and permits more erase/write cycles than EEPROM. 
3.      Power Management features  
A majority of microcontrollers usually support an operation of 3 - 5.5 V. As consumer goods become trendier, compact and lighter, the focus is on microcontrollers to ensure that products with less power usage are efficiently built and then used by end-users.
Microcontrollers are used in products that are controlled automatically.
The various products that make use of microcontrollers in our everyday life are given below:
1.    Home: Television, DVD player, Telephone, Fax machine, Cellular phones, Security systems, Camera, Sewing machine, Musical Instrument, Exercising machine, Video games, Computer, Microwave oven.  
2.       Office: Computers, Printers, Telephones, Fax machine, Security systems.

History and Key Developments

In 1975, Intel fabricated a chip (Intel 8048) with inbuilt RAM and ROM which was widely used in numerous applications. The microcontrollers had two variants namely EPROM which was erasable but expensive and PROM which could be programmed only once. In 1993, EEPROM memory was introduced in the microcontrollers which electrically erasable and at affordable price. Atmel used the Flash memory and launched the first microcontroller. After this, many companies fabricated microcontrollers with both type of memory.
The microcontroller became popular after Intel Corporation released an 8-bit version in 1981 called the 8051. Intel allowed other manufacturers to make alternate versions of the 8051, and this ensured that numerous versions of the 8051 entered the market. Some of these controllers had different speeds with multiple ROMs mounted on a single chip.
The family of 8051 microcontrollers signalled an electronic revolution with the end user reaping the benefits in technology and science.
As years passed by, microcontrollers have grown to offer much more to end-users and businesses. Some of the key developments in the microcontroller lifecycle are as follows:
1.      More ease-of-use and ability to reach market faster.
2.      More energy efficiency.
3.      More integrated features like RF and USB.
4.      Smaller form factors.
5.      Increasing processing power.
In future, MRAM (Magnetoresistive Random Access Memory) could be used in microcontrollers as it can store large amount of data which allows it to access faster consuming less power of battery.

Comparison of different families

Comparative study of different families: 8051, AVR/ATmega, PIC
General Architecture Of A Microcontroller
Fig. 3: Various Micro-controller Families : 8051, AVR/ATmega, PIC
8051: These microcontrollers are old but still trendy and most of the companies fabricate these microcontrollers. The older types of 8051 have 12 clocks per instruction that make it sluggish whereas the recent 8051 have 6 clocks per instruction. The 8051 microcontroller does not have an in built memory bus and A/D converters. In 1980, Intel fabricated the single chip microcontroller 8051 with Harvard architecture.
PIC: Programmable Interface Controller is usually referred as PIC. They are slightly older than 8051 microcontrollers but excel cause of their small low pin count devices. They perform well and are affordable.  The Microchip technology fabricated the single chip microcontroller PIC with Harvard architecture. The programming part is very tedious and hence it is not recommended for beginners.
AVR:  In 1996, Atmel fabricated this single chip microcontroller with a modified Harvard Architecture. This chip is loaded with C- compiler, Free IDE and many more features. This microcontroller is a bit difficult for the starters to handle.
Criteria for choosing a microcontroller
The most important factor is that the microcontroller should be cost-efficient and work capably to handle the dedicated task. Some questions that should be asked while deciding on a microcontroller are as follows:  
1.         What is the maximum speed of the microcontroller?
2.         What is the amount of RAM and ROM on chip?
3.         How easy it is to upgrade to higher upgrade or lower consumption versions?
4.         Is the microcontroller readily available at cheaper rates?
5.         What is the number of I/O pins and timer on the chip?

Future of Microcontroller

Future of microcontrollers and applications 
The future is bright and shining for microcontroller manufacturers. This is because the global economies are booming and microcontrollers have a role to play in almost every gadget present on earth. The list of applications for these microcontrollers is:
1.         Energy Management:
Technology for energy management is in great demand due to government initiatives that focus on energy. Efficient metering systems help in controlling energy usage in homes and industrial applications. These metering systems are made capable by incorporating microcontrollers.
2.         Touch screens:
A touch screen is accepted as the most efficient method to implement user control. They enable dynamic user interfaces and allow increased productivity. Touch screen controller implementation is microcontroller-based and therefore, ample opportunities lie ahead for microcontroller providers that incorporate touch-sensing capabilities in their designs. Portable electronics such as home appliances, cell phones, media players, gaming devices are some of the domains where microcontroller-based touch screens will be in demand. 
3.         Automobiles:
Microcontrollers find wide usage in hybrid vehicles, especially to ensure smooth and simultaneous functioning of electric and petrol engines. Additionally, almost every car manufacturer uses microcontrollers to control functions within their vehicles and to ensure error-free rides for their customers. 
4.         LED Lighting:
Microcontrollers are used for led lighting in residential and industrial locations to enable greater control and power savings.  
5.         Personal Medical Devices:
The rise and popularity of portable medical devices such as blood pressure and glucose monitors have ensured that microcontrollers will have a role in the medical industry. Microcontrollers are used to display date and increase reliability in providing medical results.




 over current,over voltage,over temprature relay etc using microcontroller

the main difference between microcontroller and microprocessor is the no. instructions in micro processor are more than micro controller, there is bitwise addresseble mode in microcontroller which is not in microprocessor

Number of instruction is defined by the terms RISC or CISC. 

R: Reduced

C: Complex

Instruction Set Computing

i totally love this theme ;-D
why is that? care to explain? just wondering ;-D


 Can you please send me a synopsis of micro-controller based project AUTOMATIC ROOM LIGHT CONTROLLER WITH VISITOR COUNTER. thanking you..

what about programming

I interested with this but it is still more and more to learn about microcontroller .

realy I want answer to this quetion :

where I can see 8051 ,PIC, AVR in real life application microwae or TV is there afemose company use any

of those MC directly or under another name.

I will highly appricheated any explain.

hai i did 5*7 dot matrix display with uln2003a driver using 89c51. my question is,its going on properly but the brightness is low. so how to improve the brightness of led dot matrix.



please help me.......................... 

u can solve ur problem to short the some pin of lcd


preset is used to improve the contrast of lcd



send any informatn available for touch based control system with microcontroller

   I am so happy to know engineering garage

   I like it so much .

What an awesome way to explain this-now I know everything!

over current,over voltage,over temprature relay etc using microcontroller plz send more details plz for my project work

Can you please help me on 'How to program AT89C51 microcontroller', using just Personal Comupter and some software?

nunber of  8051 program is available

There is a huge competition among microcontroller manufacturers. Despite this choice there are few microcontroller families that are popular .





Every now and then any techno enthusiast opens up a computer system he can automatically get to visualize some tiny microcontrollers ...

which ic are we using for avr microcontroller???


There are many tools, free and low cost demo boards available to learn about PIC microcontrollers than any other microcontrollers.

Microchip also has developer forum where we can post our queries and provide ontime support. They also share lot of demo code and demo applications which is easy to learn about embedded application development.

Things are easy with PIC!



how to a project multifucntion power meter by mcu and lcd.

get me any simple code usin mail to tis id asap  : [email protected]


i want automatic room power control using micro controller. please send me soon...


Can you please send me a synopsis of micro-controller based project AUTOMATIC ROOM LIGHT CONTROLLER WITH VISITOR COUNTER. thanking you..

Microprocessors are misused to complete big and generic applications, patch a micro controller instrument only be utilized to effect a singular strain within one use

Can you please send me a synopsis of micro-controller based project AUTOMATIC ROOM LIGHT CONTROLLER WITH VISITOR COUNTER. thanking you..

can anyone plz help me in designing a fire alarm based on gsm netork

I am doing my miniproject using 89s52 microcontroller.can any one tell me how to save 10 numbers in continous memory?ie which instruction should I use to save these numbers.............i want to save these numbers permanantly ,can i use ram for that?

and I also want to know that whether MOV A, @A+40 will work,where  A=accumulator,       40=an internal ram address......................please reply me soon..............thanking you


i wnt microprocessor basics and one project of it......please help me.......

how can i connect AT89C51 on breadboard with resistors arrays and push buttons.any 1 have idea?pls help me

how can connect AT89C51 on breadboard with reset MC, resistors arrays and push buttons?any 1 have idea pls help me.

can we do this project for at89s52


Good work

nice one. I really liked ityescheeky

The very next time I read a blog, Hopefully it won't disappoint me
as much as this one. I mean, Yes, it was my choice to read, nonetheless I really thought you'd have something helpful
to talk about. All I hear is a bunch of complaining about something you can fix if you were not too busy searching for