Introduction to Microprocessors

                                       *Introduction to Microprocessors

The microprocessor is one of the most important components of a digital computer.It acts as the brain of the computer system.
As technology has progressed, microprocessors have become faster, smaller and capable of doing more work per clock cycle.
Sometimes, microprocessor is written as ( µ is pronounced as Mu )

                                            *  Definition of microprocessor

Microprocessor is the controlling unit or CPU of a micro-computer, fabricated on a very small chip capable of performing ALU operations and communicating with the external devices connected to it.
             

                                                      * a computer

           A computerAccepts the data from the user.Stores the data and the set of instructions supplied by the user in memory.Processes the data according to the instructions in the processing unit.Communicates the result to the user or stores it for further reference.

                                               * a computer 

  A computer has the following units:
1.Input Unit

2.Output Unit

3.Memory Unit

4.Central Processing Unit

                                     * a computer                     

 * INPUT UNIT

The input unit consists of the devices which accept the data and instructions from the user and communicates it to the CPU.
The various input devices are: keyboard, mouse, joystick, trackball etc.

*OUTPUT UNIT

It provides the result of the various operations performed by the CPU to the user.
The various output devices are: printers, monitors, loudspeakers etc.

                               * CENTRAL PROCESSING UNIT (CPU)

The CPU is the heart and nerve centre of the computer.It fetches the instruction and data from the peripheral devices and performs all the arithmetic operations, takes logical decision and control the operation of all other units.

Various sub-blocks of the central processing unit are:
1.Arithmetic and Logic Unit (ALU)
2.Timing & Control Unit
3.Registers

                       *ARITHMETIC AND LOGIC UNIT (ALU)

This unit perform all the logical and arithmetic operations.Various arithmetic operations are: addition, subtraction, increment and decrement etc.

Various logical operations are: AND, OR, NOT, XOR, etc
.

                                     *TIMING AND CONTROL UNIT

This unit controls the entire operations being performed by the system.It controls the operations of ALU, input/output devices and memory unit.
This unit interprets the instructions and generates various timing and control signals.

                                                    *REGISTERS

A register is a very small amount of very fast memory that is built into the CPU in order to store the current data and instructions which are being executed by the CPU.

                                                 * MEMORY UNIT

It stores the program statement and the data i.e. the information supplied from the input unit.It also stores the final output.This is connected to the CPU by means of a bidirectional bus.The CPU processes the information as taken from the memory and performs the operations in the ALU section.The results are either transferred to the output unit or stored in the memory for later use by the CPU.

                                            * a micro computer

As the name implies, microcomputers are small computers.The block diagram of the microcomputer is similar to the computer except that the central processing unit of the microcomputer is contained in a single IC called the microprocessor.

                                                   * micro computer

A microprocessor is a LSI (Large Scale Integration) IC that does almost all the functions of the CPU.It is also defined as a CPU contained in a single chip. The basic function of the microprocessor is:
1.to fetch  the instructions stored in the main memory

2.identify the operations and the devices involved in itand accordingly generate control signals to determine when a given action is to take place.
We can say that a computer with a microprocessor as its CPU, is known as Microcomputer.

                                                * Microcomputer:

A digital computer, in which one microprocessor has been provided to act as a CPU, is called Microcomputer.A desktop computer, laptop, notebook, palmtop, etc. contain one microprocessor to act as a CPU and hence they come under the category of microcomputer.The term microcomputer is generally synonymous with personal computer.

                                                 *   Multiprocessor System: 

The CPU of a large powerful digital computer contains more than one microprocessor.High-end powerful servers, mainframe computers, supercomputers, etc. contain more than one microprocessor to act as CPU.A computer whose CPU contains more than one microprocessor is called Multiprocessor System.

                       
                                      *Microcontroller:

A highly integrated chip that contains all the components such as CPU, RAM, some form of ROM, I/O ports, and timers is called Microcontroller.Unlike a general-purpose computer, which also includes all of these components, a microcontroller is designed for a very specific task to control a particular system.

                              *Microprocessor Characteristics

      1. Instruction Set:The set of instructions that a microprocessor can understand.
2.Bandwidth:The number of bits processed in a single instruction.
3.Capability:It depends upon the number of instructions and capability of each instruction.
 4.Clock Speed:The clock speed determines how many operations per second the processor can perform.It is also called Clock Rate.Every computer contains an internal                 clock that regulates the rate at which instructions are executed and synchronizes the various computer components.The faster the clock, the more                instructions the CPU can execute per second.Clock speeds are expressed in megahertz (MHz) or gigahertz (GHz).The microprocessors of personal computers                 have clock speeds of anywhere from 300 MHz to over 3.8 GHz.
 5.Word Length:It depends upon the width of internal data bus, registers, ALU etcAn 8-bit microprocessor can process 8 bit data at a time.A processor with longer word                length is more powerful and can process data at a faster speed as compared to processor with shorter word length.The word length ranges from 4 bits for                  small microprocessor, to 64 bits for high-end microcomputers.
6.Width of Data Bus:This is the size of the data bus. It defines the number of bits that can be transferred through data bus.
7.Width of Address Bus:This parameter decides the memory addressing capability of the microprocessor. The maximum size of the memory unit is decided by this parameter.
8.Input/Output Addressing Capability:The maximum number of the input/output ports accessed by the microprocessor depends upon the width of the input/output address                                         provided in the input/output instruction.
9.Data Types:The microprocessor handles various types of data formats like binary, BCD, ASCII, signed and unsigned numbers.
10.Interrupt Capability:Interrupts are used to handle unpredictable and random events in the microcomputer.It is used to interrupt the microprocessor.Interrupt driven                          input/output improves the throughput of a system.
                                                     *Features of Microprocessor
 1.  Cost:The most important feature of a microcomputer is its low cost.Because of the widespread use of microprocessors, the volume of production is very high.
                   That is why, microprocessor chips are available at fairly low prices.
2.Size:The second important feature of a microprocessor is its small size.As a result of improvement in fabrication technology, VLSI, electronic circuitry has become                   so dense that a minute silicon chip can contain hundred and thousands of transistors.
3.Power Consumption:Another important feature is its low power consumption.Microprocessors are normally manufactured by Metal-Oxide semiconductor technology, which has                        the feature of low power consumption.
4.Versatility:The microprocessors are versatile.Keeping the same basic hardware, a microprocessor-based system can be configured for a number of applications by simply                  altering the software program.
5.Reliability:Another important property of microprocessors is its extreme reliability.It has been established that the failure rate of an IC is fairly uniform at the                 package level, regardless of its complexity.

                                                       *Micron

 1.  A unit of length equal to one millionth of a meter.
2.It is denoted by µ (Mu).
For Example:If we pluck a hair from the head, it is very thin.But a hair is more than 2000 times wider than a transistor on a microprocessor.Wires between transistors              are even thinner.They're more than 4000 times thinner than a haiA hair is about 100 microns in diameter.That means, a transistor is just 0.045 microns                 wide.