What is Microcontroller?

MCUA microcontroller is a self-contained system with peripherals, memory and a processor that can be used as an embedded system. Most programmable microcontrollers that are used today are embedded in other consumer products or machinery including phones, peripherals, automobiles and household appliances for computer systems.

Due to that, another name for a microcontroller is "embedded controller." Some embedded systems are more sophisticated, while others have minimal requirements for memory and programming length and a low software complexity. Input and output devices include solenoids, LCD displays, relays, switches and sensors for data like humidity, temperature or light level, amongst others.

Types of Microcontroller

There are several different kinds of programmable microcontrollers. We can categorized by several parameters including Bits, Flash size, RAM size,instruction set, number of input/output lines, packaging type,architecture, supply voltage and speed.

So let’s discuss;


The bits in microcontroller are 8-bits, 16-bits and 32-bits microcontroller.
  • 4-bit microcontrollers are small size, minimum pin count and low cost controllers which are widely used for low end applications like LED & LCD display drivers ,portable battery chargers etc.. Their power consumption is also low. The popular 4-bit controllers are Renasa M34501 which is a 20 pin DIP chip with 4kB of ROM,256 Bytes of RAM,2-Counters and 14 I/O Pins. Similarly ATAM862 series from ATMEL.
  • 8-bit Microcontrollers are the most popular and widely used microcontrollers .About 55% of all CPU sold in the world are 8-bit microcontrollers only.The 8-bit microcontroller has 8-bitinternal bus and the ALU performs all the arithmetic and logical operations on a byte instruction. The well known 8-bit microcontroller is 8051 which was designed by Intel in the year 1980 for the use in embedded systems. Other 8-bit microcontrollers are Intel 8031/8052 and Motorola MC68HC11 and AVR Microcontrollers, Microchip’s PIC Microcontrollers 12C5XX ,16C5X and 16C505 etc
  • When the microcontroller performs 16-bit arithmetic and logical operations at an instruction, the microcontroller is said to be a 16-bit microcontroller.16 bits microcontroller executes with greater accuracy and performance in contrast to 8-bit. These microcontrollers are having increased memory size and speed of operation when compared to 8-bit microcontrollers.These are most suitable for programming in High level languages like C or C++ .They find applications in disk drivers,modems,printers,scanners and servomotor control. 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, Automotive control, Communication networks,Robotics,Cell phones ,GPRS & PDAs etc..For EX:PIC32,ARM 7,ARM9 ,SHARP LH79520 ,ATMEL 32 (AVR) ,Texas Instrument’s –. TMS320F2802x/2803x etc..are some of the popular 32-bit microcontrollers. It requires 32-bit instructions to carry out any logical or arithmetic function.


The memory devices are divided into two types, they are
  • 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 example, 8031 has no program memory on the chip is an external memory microcontroller.

  • Embedded Memory Microcontroller: 
When an embedded system has a microcontroller  which comprise of all the functioning blocks existing on a chip it is named as embedded memory microcontroller. For example, 8051 having program & data memory, I/O ports, serial communication, counters and timers and interrupts on the chip therefore its embedded 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.

Example for CISC and RICS:

CISC: Mov AX, 4         RISC:
Mov AX, 0

Mov BX, 2

Mov BX, 4


Mov CX, 2

Begin ADD AX, BX

Loop Begin

Memory Architecture:

Memory architecture of microcontroller are two types, they are namely:

  • Harvard Memory Architecture Microcontroller
The point when a microcontroller unit has a dissimilar memory address space for the program and data memory, the microcontroller has Harvard memory architecture in the processor.
  • Princeton Memory Architecture Microcontroller
The point when a microcontroller has a common memory address for the program memory and data memory, the microcontroller has Princeton memory architecture in the processor.

Types of interfacing devices & applications with Microcontroller:




Comparison b/w ARM, 8051, AVR, PIC, MSP430