INTRODUCTION

Microcontroller are widely used in Embedded System products. An Embedded product uses the microprocessor(or microcontroller) to do one task & one task only. A printer is an example of Embedded system since the processor inside it perform one task only namely getting the data and printing it. Contrast this with Pentium based PC. A PC can be used for any no. of applications such as word processor, print server, bank teller terminal, video game player, network server or internet terminal. Software for variety of applications can be loaded and run. Of course the reason a PC can perform multiple task is that it has RAM memory and an operating system that loads the application software into RAM & lets the CPU run it. In an Embedded system there is only one application software that is typically burn into ROM. Each one of these peripherals as a microcontroller inside it that performs only one task For this reason in recent years many manufactures of general purpose microprocessors such as INTEL, Motorolla, AMD & Cyrix have targeted their microprocessors for the high end of Embedded market.

INTRODUCTION TO EMBEDDED SYSTEM

An Embedded System employs a combination of hardware & software (a “computational engine”) to perform a specific function; is part of a larger system that may not be a “computer works in a reactive and time-constrained environment. Software is used for providing features and flexibility Hardware = {Processors, ASICs, Memory...} is used for performance (& sometimes security).

An embedded system is a special purpose system in which the computer is completely encapsulated by the device it controls. Unlike a general purpose computer, such as a PC, an embedded system performs predefined task’s usually with very specific tasks design engineers can optimize it reducing the size and cost of the product. Embedded systems are often mass produced, so the cost savings may be multiplied by million of items.

EXAMPLES OF EMBEDDED SYSTEM

Automated tiller machines (ATMS).

• Avionic, such as inertial guidance systems, flight control hardware / software and letter integrated system in aircraft and missile.
• Cellular telephones and telephonic switches.
• Computer network equipment, including routers timeservers and firewalls
• Computer printers, Copiers.
• Disk drives (floppy disk drive and hard disk drive)
• Engine controllers and antilock brake controllers for automobiles.
• Home automation products like thermostat, air conditioners sprinkles and security monitoring system.
• House hold appliances including microwave ovens, washing machines, TV sets DVD players/recorders.

MICROPROCESSOR (MPU)

A microprocessor is a general-purpose digital computer central processing unit (CPU). Although popularly known as  a  “computer on a chip” is  in  no sense a complete digital computer. The block diagram of a microprocessor CPU  is  shown,  which  contains  an  arithmetic  and  logical  unit (ALU), a program counter (PC), a stack pointer (SP),some working registers, a clock timing circuit, and interrupt circuits.

Fig : BLOCK DIAGRAM OF A MICROPROCESSOR

MICROCONTROLLERS (MCU)

Figure shows the block diagram of a typical microcontroller, which is a true computer on a chip. The design incorporates all of  the  features  found  in micro-processor CPU: ALU, PC, SP, and registers. It also added the other features needed to make a  complete  computer: ROM, RAM, parallel I/O, serial I/O, counters, and clock circuit.

Fig : BLOCK DIAGRAM OF A MICROCONTROLLER

COMPARISON BETWEEN  MICROPROCESSORS & MICROCONTROLLERS

The microprocessor must have many additional parts to be operational as a computer whereas microcontroller requires no additional external digital parts.

• The prime use of microprocessor is to read data, perform extensive calculations on that data and store them in the mass storage device or display it. The prime functions of microcontroller is to read data, perform limited calculations on it, control its environment based on these data. Thus the microprocessor is said to be general-purpose digital computers whereas the microcontroller are intend to be special purpose digital controller.
• Microprocessor need many opcodes for moving data from the external memory to the CPU, microcontroller may require just one or two, also microprocessor may have one or two types of bit handling instructions whereas microcontrollers have many.
• Thus microprocessor is concerned with the rapid movement of the code and data from the external addresses to the chip, microcontroller is concerned with the rapid movement of the bits within the chip.

Lastly, the microprocessor design accomplishes the goal of flexibility in the hardware configuration by enabling large amounts of memory and I/O that could be connected to the address and data pins on the IC package. The microcontroller design uses much more limited set of single and double byte instructions to move code and data from internal memory to ALU.