Introduction to Microcontroller:
A  microcontroller  (μC  or  uC)  is  a  solitary  chip  microcomputer  fabricated  from  VLSI  fabrication.  A micro controller is also known as embedded controller. Today  various types of microcontrollers are available  in  market  with  different  word  lengths  such  as  4bit,  8bit,  64bit  and  128bit  microcontrollers. Microcontroller is a compressed micro computer manufactured to control the functions of embedded systems  in  office machines,  robots, home  appliances,  motor  vehicles,  and  a  number  of  other gadgets. A microcontroller is comprises components like - memory, peripherals and most importantly a processor. Microcontrollers are basically employed in devices that need a degree of control to be ap plied by the user of the device.


Microcontroller Basics:
Any  electric  appliance  that  stores,  measures,  displays  information  or  calculates  comprise  of  a
microcontroller chip inside it. The basic structure of a microcontroller comprise of: -
1. CPU- Microcontrol lers brain is named as CPU. CPU is the device which is employed to fetch data, decode it and at the end complete the assigned task successfully. With the help of CPU all the components of microcontroller is connected into a single system. Instruction fetch
ed by the programmable memory is decoded by the CPU.
2. Memory– In  a  microcontroller  memory  chip  works  same  as microprocessor. Memory  chip stores all programs  &  data. Microcontrollers  are built with certain amount of ROM or RAM (EPROM, EEPROM, etc) or flash memory for the storage of program source codes.
3. Input/output  ports– I/O  ports are basically employed to interface or  drive different appliances such as - printers, LCD’s, LED’s, etc.

4.Serial  Ports– These  ports  give  serial  interfaces  amid  microcontroller  &  various  other peripherals such as parallel port.
5.Timers– A  microcontroller  may  be  in-built  with  one  or  more  timer  or  counters.  The  timers  & counters control all counting & timing operations within a microcontroller. Timers are employed to  count  external  pulses.  The  main  operations  performed  by  timers’  are-pulse  generations, clock functions, frequency measuring, modulations, making oscillations, etc.
6.ADC (Analog to digital converter)–ADC is employed to convert analog signals to digital ones. The input signals need to be analog for ADC. The digital signal production can be employed for different digital applications (such as measurement gadgets).

7.DAC  (digital  to analog  converter)–this  converter  executes  opposite  functions  that  ADC perform.  This  device  is  generally  employed  to  supervise  analog  appliances  like-DC  motors, etc.
8.Interpret Control- This controller is employed for giving delayed control for a working program. The interpret can be internal or external.
9. Special   Functioning   Block– Some   special   microcontrollers   manufactured   for   special appliances  like - space  systems,  robots,  etc,  comprise  of  this  special  function  block.  This special block has additional ports so as to carry out some special operations.

Types of Microcontroller:
Microcontrollers  are  divided  into  categories  according  to  their  memory,  architecture,  bits  and
instruction sets. So let’s discuss types of microcontrollers:


8 bits microcontroller executes logic & arithmetic operations. Examples of 8 bits micro controller is Intel 8031/8051.
16  bits  microcontroller  executes  with  greater  accuracy  and  performance  in  contrast  to  8-bit.
Example of 16 bit microcontroller is Intel 8096.

32 bits  microcontroller  is  employed  mainly  in  automatically  controlled  appliances  such  as  office machines,  implantable  medical appliances,  etc.  It  requires  32 - bit  instructions  to  carry  out  any logical or arithmetic function.



  • External  Memory  Microcontroller–When  an  embedded  structure  is  built  with  a  microcontroller which  does  not  comprise  of  all  the  functioning  blocks  existing  on  a  chip  it  is  named  as  external memory microcontroller. For illustration - 8031 microcontroller does not have program memory on the chip.
  • Embedded Memory Microcontroller – When an embedded structure is built with a microcontroller which comprise of all the functioning blocks existing on a chip it is named as embedded memory microcontroller. For illustration - 8051 microcontroller has all program & data memory, counters & timers, interrupts, I/O ports and therefore its embedded memory microcontroller.

Instruction Set:
CISC- CISC means complex instruction set computer, it allows the user to apply 1 instruction as
an alternative to many simple instructions.

RISC- RISC  means  Reduced  Instruction  Set  Computers.  RISC  reduces  the  operation  time  by
shortening the clock cycle per instruction.


Memory Architecture:

  • Harvard Memory Architecture Microcontroller
  • Princeton Memory Architecture Microcontroller


8051 microcontroller:
The most universally employed set of microcontrollers   come from the 8051 family. 8051 Microcontrollers persist to be an ideal choice for  a huge group of hobbyists and experts.  In the course of 8051,  the  humankind became eyewitness to the most ground- breaking set of microcontrollers. The original 8051 microcontroller was initially invented by Intel. The two other members of this 8051 family are-

  • 8052-This microcontroller has 3 timers & 256 bytes of RAM. Additionally it has all the features of the traditional 8051 microcontroller. 8051 microcontroller is a subset of 8052 microcontroller.
  • 8031 - This microcontroller is ROM less, other than that it has all the features of a traditional 8051 microcontroller. For execution an external ROM of size 64K bytes can be added to its chip.

8051 microcontroller brings into play 2 different sorts of memory such as - NV- RAM, UV - EPROM and Flash.


8051 Microcontroller Architecture:
8051 microcontroller is an eight bit microcontroller launched in the year 1981 by Intel Corporation. It is  available  in  40  pin  DIP  (dual  inline  package).  It  has  4kb  of  ROM  (on- chip  programmable  space) and 128 bytes of RAM space which is inbuilt, if desired 64KB of external memory can be interfaced with  the  microcontroller.  There are four parallel 8  bits ports which are easily programmable  as well as  addressable.  An  on- chip  crystal  oscillator  is  integrated  in  the  microcontroller  which  has  crystal frequency of 12MHz. In the microcontroller there is a serial input/output port which has 2 pins. Two timers  of  16  bits  are  also  incorporated  in  it;  these  timers  can  be  employed  as  timer  for  internal functioning  as  well  as  counter  for  external  functioning.  The  microcontroller  comprise  of  5  interrupt sources  namely- Serial  Port
Interrupt,  Timer  Interrupt  1,  External  Interrupt  0,  Timer  Interrupt  0, External  Interrupt  1.  The  programming  mode  of  this  micro-
controller  includes  GPRs  (general purpose registers), SFRs (special function registers) and SPRs (special purpose registers).


PIC Microcontroller:
Peripheral  Interface  Controller  (PIC)  provided  by  Micro-chip  Technology  to  categorize  its  solitary chip  microcontrollers.  These  appliances  have  been  extremely  successful  in  8  bit  micro-controllers. The  foremost  cause  behind  it  is  that  Micro-chip  Technology  has  been constantly  upgrading  the appliance architecture and included much required peripherals to the micro-controller to go well with clientele  necessities. PIC microcontrollers are very popular amid hobbyists and industrialists; this is only cause of wide availability, low cost, large user base & serial programming capability.


PIC Microcontroller Architecture:
The architecture of the 8 bit PIC microcontrollers can be categorized as below-
1.Base Line Architecture-In the base-linearchitecture PIC microcontrollers of PIC10F family is included, other than that a fraction of PIC12 & PIC16 families are also included. These gadgets make use of 12 bit program word architecture with six to twenty-eight pin package alternatives.
Briefly defined attribute set of baseline architecture allows the most lucrative product solutions. This  architecture  is  perfect  for  battery  enabled  gadgets.  The  PIC10F200  series  is  another reasonably priced 8 bit flash micro-controller with a 6 pin package.

2.Mid  Range  Architecture - In  this  midline  member  of  PIC12  &  PIC16  families  are  added  that attribute 14 bit program word architecture. The midrange PIC16 gadgets proffer a broad variety of package alternatives (from  8  to  64  package), with low to high levels of peripheral
incorporation. This  PIC16 appliance attributes a variety of analog, digital & serial peripherals, like - SPI,  USART,  I2C,  USB,  LCD  &  A/D  converters. The mid-range  PIC16  micro-controllers have suspended controlling ability with an eight level hardware load.
3.High  Performance  Architecture- The  high  performance  architecture  included  the  PIC18 family  of  appliances.  These  micro- controllers  make  use  of  16  bit  program  word  architecture along  with  18  to  100  pin  package  alternatives. The PIC18 appliances are high performance micro-controllers  with  incorporated  Analog  to  Digital  converters.  All  PIC18  micro-controllers integrate a highly developed RISC architecture that supports flash appliances. The PIC18 has improved foundation attributes, 32 level deep load and several inner and exterior interrupts.


AVR Microcontroller:
AVR also known as Advanced Virtual RISC, is a customized Harvard architecture 8 bit RISC solitary
chip  micro-controller.  It  was  invented  in  the  year  1966  by  Atmel.  Harvard  architecture  signifies  that program  &  data  are  amassed  in  different  spaces  and  are  used  simultaneously.  It  was  one  of  the foremost micro-controller families to employ on- chip flash memory basically for storing program, as contrasting  to  one  time  programmable  EPROM,  EEPROM  or ROM,  utilized  by  other  micro-controllers   at   the   same   time.   Flash   memory   is   a   non-volatile   (constant   on   power   down) programmable memory. AVR Microcontroller Architecture:
AVR microcontrollers’ architecture was developed by Alf-Egil Bogen and Vegard Wollan. The name AVR  is  derived  from  the  names  of  the  architecture  developers  of  the  microcontroller.  The AT90S8515 was the foremost micro-controller which was AVR architecture based; on the other hand the  foremost  micro-controller  to  strike  the  commercial  marketplace  was  AT90S1200  which  was launched in the year 1997.


The  SRAM,  Flash  and  EEPROM  all  are  incorporated  on  a  single  chip,  thereby  eliminating  the requirement  of  any  other  external  memory  in  maximum  devices.  Several  appliances  comprise  of parallel  external bus  alternative,  so  as  to  add  extra  data  memory  gadgets.  Approximately  all appliances, except TinyAVR chips comprise serial interface, which is used to link large serial Flash & EEPROMs chips.

AMR Microcontroller:
AMR  is  the  name  of  a  company  that  designs micro-processors  architecture.  It  is  also  engaged  in licensing  them  to  the  producers  who  fabricate  genuine  chips.  In  actuality  AMR  is  a  32  bit  genuine RISC  architecture.  It  was  initially  developed  in  the  year  1980  by  Acorn  Computers  Ltd.  This  AMR base microprocessor does not have on-board flash memory. ARM is particularly designed for micro-controller devices, it is simple to be trained and make use of, however powerful enough for the most challenging embedded devices.


AMR Microcontroller Architecture:
The AMR architecture is a 32 bit RISC processor developed by ARM Ltd. Owing to its power-saving attributes, ARM central processing units are prevailing in the mobile electronics marketplace, where less power expenditure is a vital design aim.  ARM architecture comprise of the  underneath RISC elements:-

  • Maximum single cycle functioning
  • Constant 16×32 bit register file.
  • Load or store architecture.
  • Preset instruction width of 32 bits so as to simplify pipelining and decoding, at minimized code density.
  • For misaligned memory access there is no support

Microcontroller Applications:
Microcontrollers  are  intended  for  embedded  devices,  in  comparison  to  the  micro-processors  which are  used  in  PCs  or  other  all-
purpose  devices.  Microcontrollers  are  employed  in automatically managed  inventions  and  appliances  like- power  tools,  implantable  medical  devices,  automobile engine  control  systems,  ,  office  machines,  remote  controls  appliances,  toys  and  many  more
embedded systems. By dipping the size and expenditure in comparison to a design that make use of a  different  micro-processor,  I/O  devices  and  memory,  micro-controllers  formulate  it  inexpensive  to digitally control more & more appliances and operations. Mixed signal micro-
controllers are general; putting together analog constituents required controlling non-digital electronic structures.


Application of Microcontroller in Day to Day Life Devices:

  • Light sensing & controlling devices
  • Temperature sensing and controlling devices
  • Fire detection & safety devices
  • Industrial instrumentation devices
  • Process control devices

Application of microcontroller in Industrial Control Devices:

  • Industrial instrumentation devices
  • Process control devices

Application  of  microcontroller  in  Metering  &  Measurement Devices:

  • Volt Meter
  • Measuring revolving objects
  • Current meter
  • Hand-held metering systems