Microprocessor Programming Languages

Taming the microprocessor, for a particular application is done by giving instructions to the microprocessor. Instruction is a command given to the microprocessor to carry out a particular task. An instruction activates the particular logic circuit, so that a specific task will be performed. The instruction set is the set of all instructions that a specific microprocessor is intended to execute. That is a microprocessor understands only an instruction present in the instruction set of that particular microprocessor.

 

To communicate with the microprocessor, the programmer must give the instructions in the binary language because the microprocessor understands only the binary language (1s and 0s). These binary code instructions are called machine language.

 

It is tedious and error prone for people to recognize and write instructions in binary language; so these instructions are written in hexadecimal code and entered in a computer by using Hex keys.

 

For example, the binary instruction 0011 1100 is equivalent to 3C in hexadecimal. This instruction can be entered in a computer with a Hex keyboard by pressing two keys; 3 and C. The monitor program of the system translates these keys into their equivalent binary pattern.

 

Assembly language

 

It is not easy to recognize a program written in hexadecimal numbers. Therefore, every maker of a microprocessor has set up a symbolic code for every instruction called mnemonics. The mnemonic of a particular instruction consists of letters that suggest the operation to be performed by that instruction.

 

Example: The binary code 0011 1100 (3CH in hexadecimal) is represented by the mnemonic INR A. (Hexadecimal numbers are usually followed by the letter H)

 

Here INR stands for increment and A represent accumulator. This instruction suggests the operation of incrementing the accumulator content by one.

 

The complete set of 8085 mnemonics is called assembly language and a program written in these mnemonics are called assembly language program. Writing a program in assembly language is much easier and faster than writing a program in machine language. Also assembly language is specific to each microprocessor. That is, the assembly language for 8085 microprocessor is entirely different from the assembly language for Motorola 68000. A microprocessor specific language is called a low level language. Thus machine language and assembly language are microprocessor specific and are both considered as low level languages. The mnemonics are convened to machine Ianguage (binary pattern) by using a program called assembler.

High level languages

 

Programming languages that are intended to be machine independent are called high level languages. BASIC, PASCAL, C, C++, JAVA etc are examples for high level languages. Instructions written in these languages are called statements rather than mnemonics. A program written in BASIC for a computer with Intel 8085 microprocessor can generally be run on another computer with a different microprocessor (Motorola). A program written in its high level language is termed as source code.

 

The instructions written in high level language is converted to machine language by using a program called a complier or an interpreter. The compiler or Interpreter translates the source code into the machine language compatible with the microprocessor being used in the system. The machine language equivalent of the source code is also called object code.

The primary difference between compiler and interpreter lies in the process of generating machine.

 

Machine Language

 

• The program developed using 1’s and 0’s is called machine language program. The machine can understand only machine language programs.

• The program developed using mnemonics is called assembly language program. Assembler is a conversion software, which can convert assembly language programs to machine language programs.

• The machine language and assembly language programs are machine (processor) dependent.

• The language which can be used to develop software independent of the hardware (processor) are called High Level Languages.

• The compiler or interpreter is a software which can convert high level language programs to machine language programs.

Applications of Microcontrollers

Microcontrollers are also called embedded controllers or single chip microcomputers. Microcontroller is simply a computer on a chip. Microcontrollers find applications in environment where personal computers (PC) cannot be used. Following are some of its applications.

Important applications of in microcontrollers are

1. Used to measure and control the temperature of a furnace and ovens, speed of an electric motor, pressure of boilers etc.

2. Used in automobiles for automatic control of fuel and air mixture, ignition system, to test various conditions of engine, brakes etc.

3. Used in military equipments, RADAR, missiles etc.

4. Used in medical instrumentations like patient monitoring in ICU, pathological analysis, measurement of physiological parameters etc.

5. Used in home appliances like washing machines, microwave ovens etc where some physical parameters are monitored and controlled.

6. Used in electronic toys making them more entertaining and easy to use.         

7. They are widely used in controlling pumps, alarms, and other power applications. It is also used in communication equipment.

8. The Microcontroller output is binary values, but application equipments display, motor, speakers etc. work in analog signal.

9. There are many applications where you have to display numbers. The most popular display device used for displaying number is seven segment LED displays.

10. Microcontroller keeps the speed of the motor as constant. It adjusts the speed of the motor by changing the duty cycle of the signal applied to it. Hence constant speed can be maintained.

11. The electro mechanical relays have been used for many years in industry to control high dc or ac voltages and currents. Relays also provide isolation between the controller and the circuit under control.

12. It helps in Keyboard interfacing. When a key is pressed, the microcontroller identifies the pressed key by using either a software based or hardware based technique and then performs the assigned operation.

13. It helps in Stepper Motor interfacing. In order for getting accurate position control of rotating shafts, the Microcontroller 8051 is connected to it for constant speed.

Communication System Block Diagram Explanation

 

Communications Systems

 

The process of transmission of information or message from one end to another is known as communication. When electromagnetic or radio waves are utilized for communication purpose, then it is called as radio communication. Electronic communication is started with wire telegraphy in the first half of nineteenth century. After a decade of years, telephony was developed, In the beginning of the twentieth century, radios come into existence. Radio communication made possible by the invention of the triode tubes. 

 

The modern communication system involves the process of sorting, processing and storing of information before conveying the message. During transmission, the filtering of noise takes place. Finally there includes the processing steps like decoding, storage and interpretation. Some types of communication include radar, telecommunications, mobile, computer, radio telemetry etc. The essential requirements of any communication system are fundamentally same.

 

Communication System Block Diagram with Explanation

 

The general block diagram of a general communication system is shown in figure. Any communication system is consist of an information source, transmitter, receiver, channel and noise.

 

Information

 

The purpose of communication system is to communicate a message. This message comes from an information source. The message from an information source may be a speech from an individual or a numerical data from a computer. The total number of messages consists of individual messages which can be distinguished from one another. The amount of information contained in any given message is measured in bits depending upon the method of communication.

 

Transmitter

 

The message comes from an information source may not be an electrical signal. Unless the message that comes from the information source is electrical in nature, it will be unsuitable for sending. So the physical quantity must be converted into an electrical signal before it is applied to the transmitter. This is done with a transducer. The transducer will convert the physical quantity (in which the information is presented) into a corresponding electrical signal. For example, a carbon microphone will convert sound into electrical signal. The output from the transducer is known as signal. The signals are of two types — analogue type or digital type. According to the type of signals used, communication systems are also classified into either analogue or digital systems. In modem communication systems, the analogue signals are converted into digital signals, and thereafter transmitted through a digital system.

 

Even though the message that comes from the information source is electrical in nature, it is unsuitable for immediate sending. A lot of process must be done on the message to make it suitable for transmission. The transmitter is required to process the incoming information. The main process to be done is known as modulation. Modulation is a process in which some characteristics of a high frequency sine wave (carrier) is varied in accordance with the instantaneous values of the message signals. In a transmitter, the information modulates a carrier. That is, the information is impressed on a high frequency sine wave. The method of modulation may be analog or digital, high level or low level. The system may be amplitude modulator, frequency modulator, phase modulator, or pulse code modulator or combination of these.

 

Channel

 

Channel is the medium through which the information is transmitted from the transmitter to the receiver. The channel may be free space, air, wire, or fiber optic channel. In radio communication, the medium is free space where as in line communication it is a cable or a wire. In radio communication, information is transmitted as electromagnetic waves into the free space. In line communication it is transmitted as electric signals through cable. The acoustic channel is not used for long distance communication.

 

Noise source

 

The reason for noise is

 

1. Some distortion in the system

2. Because of introduction of noise, which is present in a transmission system.

 

Noise is defined as any unwanted form of energy tending to interfere with the proper and easy reception and reproduction of wanted signals. Noise can interfere with the signal at any point in a communication system. There are many ways of classifying noise, It is most convenient here to divide noise into two broad groups — internal noise and external noise.

 

External noise is the noise whose sources are external to the receiver. For example, atmospheric noise and industrial noise. Internal noise is the noise created within the receiver itself. For example, thermal agitation noise.

 

Receiver

 

The transmitted signal finally reaches at the receiver. The main function of a receiver is to demodulate the modulated incoming signal so as to retrieve the original message. The signal from the channel is amplified and the information is extracted in the desired form with the help of a transducer.

Modulation and Need for Modulation

 

Modulation and Need of Modulation

Modulation may be defined as a process by which any characteristics of a wave is varied as a function of the instantaneous value of another wave. The first wave, which is normally a high frequency sine wave, is known as carrier wave. The second wave is known as the modulating wave and the resultant wave is known as the modulated wave. The rate at which the variation takes place is equal to the modulating wave frequency. Modulating signal is an electrical signal having sound, picture or any other type of information.

Audio frequencies ranges from 20 Hz to 20 KHz. Sound waves propagated in air directly beyond a few hundred meters. Radio frequency means anything above 20 KHz. Radio waves are electromagnetic in nature, are capable of being propagated upto infinite distance in space. Sound waves can be able to propagated upto infinite distance in space. Sound waves can be able to propagated upto infinite distance in space by superimposing them on radio waves. This is what is done by the modulation process.

A carrier sine wave can be represented by the equation, e = Esin(ωt+φ), where ‘e’ is the instantaneous value of carrier sine wave, E is the maximum amplitude, ω is the angular frequency and φ is the phase. An unmodulated carrier has constant amplitude, a constant frequency and a constant phase relationship with respect to some reference. In modulation process one of these three parameters of the carrier may be varied by the modulating wave or signal. Hence at any moment its variation from the unmodulated value is proportional to the instantaneous value of modulating voltage. Depending on which characteristics of the carrier is varied by the modulating signal, there are three types of modulation – amplitude, frequency or phase modulation. The need for modulation is explained below.

1. The height of the antenna required for transmission and reception of a signal must be equal to ¼ th of the wavelength of the signal used for communication. We know, f = C/λ, where f is the frequency used, C is the velocity of the electromagnetic wave and λ is the wavelength. If frequency is small, λ is high and hence height of the antenna required must be comparatively large. If frequency is large, λ is small and hence height of the antenna required must be comparatively small. For example, a 15 KHz electromagnetic wave has a wavelength of λ = 3 x 10⁸/15 x 10³ = 20,000 m. Therefore the height of the antenna is λ/4 = 20,000/4 = 5000 m or 5 Km. Therefore the 15 KHz signal requires an antenna of 5 Km height. A vertical antenna of this size is unthinkable. Since the frequency is inversely proportional to the antenna height, a higher frequency must be used to reduce the antenna height.

2. At low frequencies, the transmitting power must be very large. The construction of a transmitter having such a huge power handling capacity is a difficult task. A radio frequency signal will travel a greater distance than the same amount of energy transmitted as sound signal.

3. All sound signals are within the range of 20 Hz to 20 KHz. If we transmit these sound waves directly, all waves from different stations and sources would be inseparably mixed up. In order to separate the various signals from different stations, it is necessary to transmit them at different portions of electromagnetic spectrum. This will also overcome the poor radiations at low frequencies. A tuned circuit is used in the receiver to select a desired transmission within a predetermined range and to reject all the other unwanted signals.

Fundamentals of Electromagnetic Waves

 

Electromagnetic waves are oscillations that transmit through free space with the velocity as that of light. Free space is the space that does not interfere with the normal radiation and propagation of the radio waves. Free space has no magnetic or gravitational field, no solid bodies and no ionized particles. Free space is unlikely exist anywhere. However the concept of free space is used because it simplifies the approach to wave propagation. Radio waves are electromagnetic in nature, has an electric field and magnetic field. Electromagnetic are transverse wave, that the oscillations are perpendicular to the direction of propagation. Also the direction of electric field, magnetic field and the direction of propagation are mutually perpendicular to each other.

Polarization: Polarization is refers to the physical orientation of the radiated wave in space. A wave is said to be vertically polarized, when all its electric intensity vectors are vertical. A wave is said to be horizontally polarized when all its electric intensity vectors are horizontal. A vertical antenna will radiate vertically polarized wave and a horizontal antenna radiates horizontally polarized waves.

Reflection: Electromagnetic waves will be reflected by a conducting medium. They will be reflected by ground, mountains and buildings. This is much similar to the reflection of light by a mirror.

Refraction: Refraction takes place when electromagnetic waves pass from one propagating medium to another medium having a different density. They will get refracted as they pass through the layers of the atmosphere having different degrees of ionization.

Diffraction: Diffraction of electromagnetic waves occurs due to the presence of small slits in a conducting plane or sharp edges of obstacles. The electromagnetic waves may be diffracted around the tall massive objects.

Attenuation and absorption: The power density of the wave diminishes rapidly with distance from the source of electromagnetic waves. The attenuation is proportional to the square of displacement. In free space, absorption of radio waves does not occur because there is nothing to absorb them. However atmosphere is tend to absorb radio waves because some of the energy from the wave is transferred to the atoms and molecules of the atmosphere. Thus the energy of the waves may be absorbed quite significantly.

Ground Wave Propagation:

Frequency below high frequency range { very low frequency (3 KHz to 30 KHz), low frequency (30 KHz to 300 KHz) and medium frequency (300 KHz to 3 Mhz)} will travel along the curvature of the earth. So these waves are called the ground waves or surface waves. Ground waves are propagated by means of a type of waveguide effect, which uses the earth surface and the lowest ionized layer of the atmosphere as the two waveguide walls. Ground wave propagation is one of the two means of the beyond the horizon propagation. Ground waves must be vertically polarised to prevent the short circuit of the electric field components.

A ground wave is attenuated in two ways.

1. A wave induces currents in the ground over which it passes and they loses some of energy by absorption.

2. Because of the diffraction the wave front gradually tilts over as the wave propagate over the earth, its tilts increases more and more and increasing the tilt causes greater short circuiting of the electric field component of the wave and hence the field strength reduction. Eventually at some distance from the antenna the waves lies down and dies.

Use: Medium wave radio communication

Sky wave propagation

The ionosphere is the upper portion of the atmosphere which absorbs a large quantities of the energy from the sun, it becoming get heated and ionized due to the heat. There were several degrees of ionization at different height. The various layers of ionosphere have specific effects on the propagation of radio waves particularly at high frequency. Under certain conditions, waves in the high frequency range (3 MHz to 30 MHz) are return to the earth by the ionized layers of atmosphere so they are called sky waves. The mechanism involved in this process is refraction. The ionization density increases for a wave approaching the given layer (ionosphere) at an angle, so the refractive index of the layer is reduced. Hence the incident wave gradually bends further and further away from the normal. At a particular layer it will bend downward and finally emerging from the ionized layer at an angle equal to the angle of incidence as shown in figure. This is the second method for the beyond the horizon propagation.

Skip distance

It is the distance upto which sky waves of given frequency cannot be received or minimum distance from transmitting antenna to the point at which sky wave of a given frequency is returned to earth by ionosphere. It depends on frequency of transmission, critical frequency, and height of layer and increases as ionization in the layer reduces. It is the shortest distance measured along the surface of the earth at which a sky wave of fixed frequency will be returned to the earth.

Use: Short wave communication.

Frequency above high frequency range generally travels through the troposphere, the portion of the atmosphere closest to ground. So space waves are sometimes called troposphere waves. Space wave propagation depends on line of sight (LOS) conditions. So the space waves are limited in this propagation by the curvature of earth. When earth curvature can be neglected, space wave propagation take place in the manner illustrated is shown in the figure.

Here energy reaches the receiver in two ways

1. By a ray travelling directly between transmitting and receiving antennas (Direct wave).

2. By a ray that reaches the receiver after reflection from the surface of the ground (Ground reflected wave) or Satellite reflected wave.

The field strength at the receiving antenna is the vector sum of the fields represented by the two rays.

Cable meaning in Electronics

What is Cable in Electronics?

Cable

It is an insulated bundle of metal wires or threadlike fibres that carry electric current. They are widely used to distribute electric power and to transmit communication signals. They are also used to connect parts of computers and other electronic devices. Fiber optic cables have also been developed which transmit communications signals in the form of pulses of light. Most communications cables consist of conductors and insulation. Simple cables are made up of a single pair of insulated wires twisted together. Multiconductor cables such as telephone lines contain, hundreds or even thousands of conductors bound together. Submarie cables serve as a communication link between continents. In 1844 American painter and inventor Samuel F.B. Morse completed the first long distance telegraph cable in America.

Coaxial Cables

They are made up of special conductors called coaxials. A coaxial is a copper tube with a copper wire running through its centre. Insulation holds the wire in place. The tube and the wire have the same axis and are therefore called coaxials. A typical coaxial has about the same diameter as a pencil. Many telephone calls, especially long distance calls travel over coaxial cables. When used for telephone conversations coaxial work in pairs. One coaxial carries signals in one direction and the other carries signals in the other direction. Cable television systems use coaxial cables to transmit TV programmes.

Cable Television

Television programmes transmitted to viewers via wires from the broadcasting station constitute a cable television system. Since their initial introduction in the 1970’s cable systems have become common in areas well enough populated to be financially feasible. By 1988, 50% of the US households subscribed to cable television. In recent years, there has been some use of fiber cables instead of conventional copper or aluminium cables. Channel selectors allow for reserving certain channels to subscribers who have paid extra for access.

Cable Railway or Cable Car

Railways running on aerial cables were invented in the later half of 17^th century and early half od 18^th century to move coal from coal mines to the harbours by crossing the hills and mountains. Now the cable railways are mostly used for ski resorts and other tourist attractions. The ccapacity of passenger units varies from chairs to cabins that can hold more than hundred passengers. The first street railway to run on underground cables was developed by Andrew Hallidie in the San Francisco (USA) in the year 1873. The complex cable systems were subject to breakdowns and need much energy. It was in the beginning of 19^th century, electric street cars began to replace cable railways.

Abacus and Calculator meaning in Electronics

Abacus and Calculator meaning in Electronics

Abacus

Abacus is a calculating device which consists of balls strung on wires or rods set in a frame. It is almost certainly of Babylonian origin but its use decreased in Europe with the beginning of Arabic numerals in about the 10^th century AD. Until recently it was still use in the Middle East and Japan. Ancient types of abacus have also been found in China, thought that same to have taken there by Arabic traders. The first known use of them in China was during the twelfth century where the device was called the ‘Suan-Pan’. It can be used to do mathematical functions such as addition, subtraction, multiplication and division and to calculate square roots and cube roots.

Calculator

                       

It is a device that adds, subtracts, multiplies and divides with accuracy and speed. A mechanical calculator was built by the German mathematician Wilhelm Schickard in 1623 using a set of metal wheels. Around 1642 the French Mathematician Blaise Pascal made a similar machine that could handle up to nine digit numbers. In 1673, the German Mathematician Gottfried Lelbniz made a device similar to Pascal’s. Beginning in the 1960’s electronic calculators and digital computers became very popular. Besides adding, subtracting, multiplying and dividing many electronic calculators perform more complicated functions such as extracting square roots and cube roots. Many models also contain a memory in which numbers and instructions for solving problems can be stored for future use.