Advantages And Disadvantages Of Serial And Parallel Data Transmission

Data transmission is the transfer of data from point-to-point often represented as an electro-magnetic signal over a physical point-to-point or point-to-multipoint communication channel. Examples of such channels are copper wires, optical fibers, wireless communication channels, and storage media. T he term usually refers to digital communications (i.e. Digital bit stream), but may include analog data transmission as well. Data transmission is a subset of the field of data communications, which also includes computer networking or computer communication applications and networking protocols, for example routing and switching.

Parallel transmission is a method of transmitting data where each bit in a byte is transmitted in an individual channel or wire, hence multiple bits can be sent at the same time. Parallel transmission is often used internally in a computer since it is quick and the distances involved are short, a s well as in devices such as disk drives, joysticks and a majority of printers. Parallel transmission, however, has the disadvantage of bits getting out or order when transmitted over a long distance. This is known as data skew.

The advantages and disadvantages of serial links in communication system design. This ideal serial solution offers a powerful integration of programmable logic and this high-performance serial interface. This flexible solution offers a variable data rate, and compliance with a broad range of standards.

Data Communication & Computer Networks: Serial and parellel transmission • 1. Introduction to Data communication Topic: Serial & Parallel Transmission Lecture #4 Dr Rajiv Srivastava Director Sagar Institute of Research & Technology (SIRT) Sagar Group of Institutions, Bhopal • Unit 1 Lecture 4 • Serial Transmission • In Serial Transmission, the bits of a byte are serially transmitted one after other.

• The shift register is used for serial transmission. • The byte to be transmitted is the first stored in a shift register. • Then these bits are shifted from MSB to LSB bit by bit in synchronization with the clock. Bits are shifted right by one by one position per clock cycle. • As an advantage only one wire is used in serial transmission between the transmitter and the receiver.

3 • 4 Serial Transmission • Some examples of serial Communication Devices • Morse code telegraphy • RS-232 (low-speed, implemented by serial ports) • RS-422 • RS-423 • RS-485 • Ethernet • SONET and SDH • T-1, E-1 Lines • Advantages of serial transmission • Only one wire is required • Reduction in cost due to less number of conductor wires • It is the most used method for long distance data transfers. Disadvantages of serial transmission • Since there is only one line of transmission therefore the speed of transmission is quite slow. • If we have to increase the speed of data transfer then it is necessary to increase the clock frequency. But there is a limit of clock frequency.

6 • Serial transmission has two categories: 1. Synchronous data transmission 2. Asynchronous data transmission 7 Types of serial transmission?

• Asynchronous Data Transmission • It is called asynchronous because timing of the signal is not an issue. The information can be sent & received as per mutual agreement of the sender & receiver. • asynchronous transmission is at byte level only because transmission of bits is always synchronized. 8 0 Data Byte 1 Idle time 0 Data Byte 1 Idle 0 Start Stop • • Asynchronous transmission is eased by two its, a ely start it as & stop it as. • We se d it to start the o u i atio & it to stop the tra s issio. • There can be a time delay between communication of two bytes.

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• Only one byte is sent at a time. After a gap of time next byte is transmitted. • The transmitter and receiver may function at different clock frequencies. • Asynchronous transmission is mostly used by asynchronous modems. • Operation Before signalling will work, the sender and receiver must agree on the signalling parameters: • Full or half-duplex operation • The number of bits per character • the order in which the bits are sent • The speed or bits per second of the line (often incorrectly referred to as the Baud rate). Some systems use automatic speed detection.

• Whether to use or not use parity • Odd or even parity, if used • The number of stop bits sent must be chosen (the number sent must be at least what the receiver needs) • 11 Asynchronous Transmission • Why it is called Asynchronous? This mechanism is called as Asynchronous because at the byte level the sender and receiver do not have to be synchronized. However within each byte, the receiver should still be synchronized with the incoming bit stream. This means that some synchronization is required only for the duration of single byte. 12 • Advantages of Asynchronous transmission Asynchronous transmission has many advantages these are: • It is a flexible data transmission method.

• Synchronization between the transmitter and receiver is not necessary. • It is possible to transmit signals from the sources having different bit rates. • The transmission can commence as soon as the data byte to be transmitted becomes available. • This mode of transmission is easy to implement. • It is an effective scheme.