DigiCom Mod 1-4 PDF

M1: Introduction to Data Communications Five Components of Data Communications Data Communications defined: 1. Message – The message is the information (data) to...

M1: Introduction to Data Communications Five Components of Data Communications Data Communications defined: 1. Message – The message is the information (data) to be communicated. Popular forms of information The movement of computer information from one point to include text, numbers, pictures,audio,and video. another by means of electrical or optical transmission systems. 2. Sender – The sender is the device that sends the data The transmission, reception, and processing of digital message. It can be a computer, workstation, information. telephone handset, video camera, and so on. 3. Receiver – The receiver is the device that receives the Process of transferring digital information between two or message. It can be a computer, workstation, more points. telephone handset, television, and so on. 4. Transmission Medium – The transmission medium is Data communications are the exchange of data between two the physical path by which a message travels from devices via some form of transmission medium such as a wire sender to receiver. Some examples of transmission cable. media include twisted-pair wire, coaxial cable, Keywords: fiberoptic cable, and radio waves. 5. Protocols – rules and conventions used in order to Transmission, reception, process, point to point, data, exchange information in a Data Communications information, computer. network. Data Communication is a system consisting of different Telecommunications Data Network components that can transport, receive and process data. Data are the information and can be of several formats. (audio, video, bits, digital info) Importance of Data Communications Computers need to communicate. Computers need to communicate with the peripherals. Electronic equipment need to communicate. Data need to be secured and delivered between devices. Block Diagram of Basic Data Communications System Brief History of Data Communications and Telecommunications 1837 - Samuel Morse exhibited a working telegraph system. 1843 - Alexander Bain patented a printing telegraph. 1876 - Alexander Graham Bell, invented the first telephone. 1880 - first pay telephone 1915 - first transcontinental telephone service and first transatlantic voice connections. 1947 - transistor invented in Bell Labs DTE and DCE Role in Data Communications DTE ( DataTerminal Equipment) 1951 - first direct long distance dialing These are the end devices that is used to deliver the message 1962 - first international satellite telephone call in that can be understood end to end. 1968 - Carterfone court decision allowed non-Bell equipment DCE (Data Communications Equipment) to connect to Bell System Network Another term for the MODEM( Modulator-Demodulator) 1970 - permitted MCI to provide limited long distance service equipment. The equipment used in long distance serial data in competition to AT&T. communication system responsible for different modulation techniques. 1984 - deregulation of AT&T Data Terminal Equipment Examples 1980s - public service of digital networks WIFI Router 1990s - cellular telephones commonplace Router (Cisco 1921 Series) Computer Servers Phases of Telecommunication Development Data Communication Equipment Examples Telegraph &Telephone (19th century) Dial Up Modem Satellite communications (1960s) USP Plug – In Modem Digital communications (1980s) Pocket WIFI Internet age (1990s) DSL Modem Wireless communications (1990s) Cable Modem Satellite Modem 21st century? V.35 Modem Trends: From wired to wireless, from analog to digital, from voice, video, picture to data  Data Representation Two Basic Types of Electronic Communication Systems Text – alphanumeric characters represented as bit patterns Analog Communication System – system in which signals are (sequence of bits, 1 and 0). Each set is called a code. transmitted and received in analog format. Numbers – also represented as bit patterns, in data Digital Communication System – system in which signals are communications, the numbers are converted to binary transmitted and received in digital form. ( discrete levels such equivalent. as +Volts, -volts and 0 volts). Images – it is also represented as bit patterns, composed of a Note; In a Data Communication System, both analog and matrix of pixels (picture elements) where each pixel is a dot. digital system can be incorporated. Audio – recording or broadcasting of sound or music. Continuous form Analog and Digital Signals in a Transmission System Video – recording or broadcasting of a picture or a movie. Common Terms used in Data Communications Information – knowledge or intelligence , (analog/digital) Data – information stored in digital format Data Transmission Code – information converted to a binary code. Data Communication Code – Used to represent characters or symbols. Includes character codes, character sets, symbol codes, character languages. Bandwidth – range of frequencies contained in a frequency spectrum. It is used to define a particular channel in a transmission system. Information Theory – a highly theoretical study of the efficient Data Transmission Modes (Data Flow) use of bandwidth to propagate information through electronic Simplex - communication is unidirectional. Only one of the two communication systems. devices on a link can transmit; the other can only receive. Bit – binary digit. It’s the most basic digital symbol used to Half duplex - Only one of the two devices on a link can represent information. It could be a 1 or 0. transmit; the other can only receive Mark – refers to binary 1 Full duplex - both stations can transmit and receive Space – refers to binary 0 simultaneously. Block/Frame/Packet – group of bits transferred as a unit. Bit Rate – rate of change of a digital information signal. It is Networks also referred to the number of bits transmitted per second. Network is a set of devices (often referred to as nodes) Information Capacity – measure of how much information can connected by communication links. A node can be a computer, be propagated through a communications system. Represent printer, or any other device capable of sending and/or the number of independent symbols that can be carried receiving data generated by other nodes on the network. through a system in a given unit of time. It is usually dependent on the frequency and bandwidth. Most networks use distributed processing, in which a task is Baud Rate – refers to the rate of change of signal in a divided among multiple computers. Today it can be referred to transmission (communications) medium after encoding and a cloud computing. modulation have occurred. Number of signaling element per second in a transmission medium. It is equal to 1/time of one Network Criteria output signaling element. A network is evaluated using the following network criteria; Station or Node – an endpoint where subscribers gain access performance, reliability and security to the data communications circuit. Communications Link –.path for transmission of signals Performance is the effectiveness of the network which is often between communicating devices. evaluated in terms of two metrics; throughput and delay. Data Communications Circuit – provides a transmission path (accuracy of delivery). Transit time and response time is used between locations used to transfer digital information from in measurement of the metrics. one station to another. Transit Time – time required for a message to travel from one Channel – specific band of frequencies allocated to a particular device to another. service of transmission. Response Time – time elapsed between inquiry and response. Protocol – formal set of conventions governing how Reliability is based on the frequency of failure measurement. communications should take place in a communications It’s the ability of the network to recover from a network link system. failure and the networks robustness in a catastrophe. Protocol Stack – the list of protocols used by a system. Security – protecting data from unauthorized access, Network – set of devices (nodes or stations) interconnected by protecting data from damage and development, and communications media link. implementing policies and procedures for recovery from Data Communications Network – Systems of interrelated breaches and data losses computers and computer equipment that are interconnected to one another for the purpose of transmitting and/or Types of Network Connection receiving of information. Point to Point – dedicated link between two devices Computer Network – two or more computers interconnected Multipoint – multiple connection in a single link. Also called with one another for the purpose of sharing resources such as multidrop. printers, databases, files and backup devices. Network Topologies: A review in Computer Networks Mesh, Analog Signal – signal whose amplitude continuously varies Bus, Star, Ring with time. Note: In a mesh topology, the number of links (L) is equivalent Digital Signal – signal which are discrete, their amplitude to n(n-1)/2 where n is the number of stations or nodes to be maintains a constant level for a prescribed period of time. connected.  M2: Codes used in Data Communications ITU International Morse Code Data Communication Codes In Data Communications, all information must be converted into binary codes. Codes used for text and character information are called character codes, character sets or character symbols. Morse Code (International Morse Code) First character set which was developed by Samuel Morse. Variable Length Source Code which uses dot, dash, and space symbols Each character (letter or numeral) is represented by a unique sequence of dots and dashes (dits and dahs). The duration of a dash is three times the duration of a dot Each dot or dash within an encoded character is followed by a period of signal absence, called a space, equal to the dot duration. The letters of a word are separated by a space of duration equal to three dots, and words are separated by a space equal to seven dots. There is no distinction between upper and lower case letters. Morse code is usually transmitted by on-off keying of an Examples: information-carrying medium such as electric current, radio Morse Code Keyer waves, visible light, or sound waves. Telegraph Key and Sounder Was used in telegraph, not suited for modern data communications Important Morse Code used in Emergency and Distress Literally requires reasoning ability of human brain to decode. In Morse Code, "SOS" is a signal sequence of three dots, three Morse Code Versions dashes, and another three dots spelling "S-O-S". The Historical versions of Morse code with the current standard. expression "Save Our Ship" was probably coined by sailors to signal for help from a vessel in distress. Left: Later American Morse code from 1844. Center: The modified and rationalized version used by This can be sent many ways: Friedrich Gerke on German railways. 1. keying a radio on and off, Right: Current ITU standard. 2. flashing a mirror, 3. toggling a flashlight, and similar methods. The SOS signal is not sent as three separate characters; rather, it is a prosign SOS, and is keyed without gaps between characters. BAUDOT CODE Named after Emil Baudot who invented the first constant length teleprinter in the 1870s. Fixed length 5-bit code used for telegraph, and is also called Telex code. Less characters / codes can be used (25) Uses figure shift and letter shift control characters to expand its capability to 58 characters. The symbol rate measurement is known as baud, and is derived from the same name. Baudot's code became known as the International Telegraph Alphabet No. 1 (ITA1). It is no longer used. Baudot's 5-bit code was adapted to be sent from a manual keyboard, and no teleprinter equipment was ever constructed that used it in its original form. The code was entered on a keyboard which had just five piano- type keys and was operated using two fingers of the left hand and three fingers of the right hand. Once the keys had been pressed, they were locked down until mechanical contacts in a distributor unit passed over the sector connected to that particular keyboard, at which time the keyboard was unlocked ready for the next character to be entered, with an audible click (known as the "cadence signal") to warn the operator. Operators had to maintain a steady rhythm, and the usual speed of operation was 30 words per minute.  Unicode 14.0 is now in beta with 144,697 characters, including 5 new scripts, and 37 new emoji characters. The standard has been implemented in the modern operating systems, XML, the Java programming language, and the Microsoft.NET Framework. Two Mapping Methods of Unicode 1. UTF ( UnicodeTransformation Format) 2. UCS ( Universal Character Set) The numbers in the names of the encodings indicate the number of bits in one code value (for UTF encodings) or the number of bytes per code value (for UCS) encodings. AMERICAN STANDARD CODE FOR INFORMATION INTERCHANGE (ASCII) UTF Encodings It is 7-bit code standardized by ITU as International Telegraph UTF-1 – a retired predecessor of UTF-8, maximizes Alphabet #5 (ITA#5), ASCII contains 128 code words. compatibility with ISO 2022, no longer part ofThe Unicode ASCII was developed from telegraph code. Standard. Its first commercial use was as a seven-bit teleprinter code UTF-7 – a 7-bit encoding sometimes used in e-mail, often promoted by Bell data services considered obsolete (not part of The Unicode Standard, ASCII is the coding scheme used almost universally with butonly documented as an Informational RFC, i.e. not on the personal computers and other devices such as keyboards, Internet Standards Track either). printers, and the like. UTF-8 – an 8-bit variable-width encoding which maximizes Most often, 7-bit ASCII code is converted to 8-bit code by the compatibility with ASCII. The dominant encoding on the World addition of a parity bit to check the correctness of Wide Web (used in over 95% of websites as of 2020, and up to transmission. 100% for some languages) and on most Unix-like operating ASCII Code Sample Application systems, uses one byte (8 bits) for the first 128 code points, and up to 4 bytes for other characters. Microsoft Word UCS-2 – uses a single code value (defined as one or more Extended ASCII Code numbers representing a code point) between 0 and 65,535 for each character, and allows exactly two bytes (one 16-bit word) Developed by IBM to represent that value. Forbids using parity bit UCS-4 – uses a single code value between 0 and (theoretically) All 8 bits can be used to represent characters. hexadecimal 7FFFFFFF for each character. Codes 00 hex to 7F hex are backward compatible to standard ASCII code. The Unicode Consortium The Unicode Consortium is a nonprofit organization that EBCDIC (Extended Binary Coded Decimal Interchange Code) coordinates Unicode's development. Code developed by IBM Used mainly on IBM mainframe and IBM midrange Full members include most of the main computer software and computer operating systems. hardware companies with any interest in text-processing Uses 8 bits (256 codes possible) standards, including Adobe, Apple, Facebook, Google, IBM, Does not facilitate the use of parity bit Microsoft, Netflix, and SAP SE. LSB is designated b7, MSB is designated b0, such that b7 is transmitted first and b0 is transmitted last. Unicode Consortium Members UNICODE It is an information technology standard for the consistent encoding, representation, and handling of text expressed in most of the world's writing systems. The standard, which is maintained by the Unicode Consortium, defines 143,859 characters covering 154 modern and historic scripts, as well as symbols, emoji, and non-visual control and formatting codes.  BAR CODES It is an optical machine-readable representation of data The purpose of UPCs is to make it easy to identify product relating to the object to which it is attached. Originally features, such as the brand name, item, size, and color, when barcodes systematically represented data by varying the an item is scanned at checkout. UPCs are also helpful in widths and spacings of parallel lines, and may be referred to as tracking inventory within a store or warehouse. linear or one-dimensional (1D). Later they evolved into rectangles, dots, hexagons and other geometric patterns in To obtain a UPC for use on a product a company has to first two dimensions (2D). apply to become part of the system. GS1 US, the Global Standards Organization, formerly known as the Uniform Code It was invented by Norman Joseph Woodland and Bernard Council, manages the assigning of UPCs within the US. Silver and patented in the US in 1951. UPC Code Composition: The invention was based on Morse code that was extended to Each UPC-A barcode consists of a scannable strip of black bars thin and thick bars. However, it took over twenty years before and white spaces above a sequence of 12 numerical digits. this invention became commercially successful. No letters, characters or other content of any kind may appear The Uniform Grocery Product Code Council had chosen, in on a UPC-A barcode. 1973, the barcode design developed by George Laurer. Laurer's barcode, with vertical bars, printed better than the There is a one-to-one correspondence between 12-digit circular barcode developed by Woodland and Silver. Their use number and strip of black bars and white spaces. has spread to many other tasks that are generically referred to as Automatic Identification and Data capture (AIDC). Examples of Barcodes: Code 39, Universal Product Code, POSTNET Bar Code Code 39 – CODE 39 is the barcode developed by Intermec Corporation in 1975. Up to 43 characters including numbers, letters and some symbols can be included in the barcode. Since letters can be handled, CODE 39 is indispensable in the industrial fields and used in industries such as automotive and The scannable area of every UPC-A barcode follows the electronics. It is standardized by AIAG (Automotive Industry pattern SLLLLLLMRRRRRRE, where S (start), M (middle), and E Action Group) in U.S.A. (end) guard patterns. The L (left) and R (right) sections collectively represent the 12 numerical digits that make each CODE 39 is named for its pattern of bars and spaces, with 3 out UPC-A unique. of 9 bars and spaces being wide. The first digit L indicates a particular number system to be used Code 39 Basic Composition: by the following digits. One letter (character) is represented by 9 bars and spaces. Asterisks (*) are attached to the start and end of the barcode. The last digit R is an error detecting check digit, that allows (start/stop character) some errors to be detected in scanning or manual entry. The The space between characters is called an "inter-character guard patterns separate the two groups of six numerical digits gap". Generally, the gap width is as wide as the narrow bar and establish the timing. width. (The maximum width is ruled to be 3 to 5.3 times wider than that of the narrow bar.) The guard patterns separate the two groups of six numerical digits and establish the timing. POSTNET (Postal Numeric Encoding Technique) Bar Code: It is a barcode symbology used by the United States Postal Code 39 Character Representation: Service to assist in directing mail. The ZIP Code or ZIP+4 code is encoded in half- and full-height bars. Most often, the delivery point is added, usually being the last two digits of the address or PO box number. Each individual digit is represented by a set of five bars, two of which are full bars. The full bars represent "on" bits in a pseudo-binary code in which the places represent, from left to right: 7, 4, 2, 1, and 0. (Though in this scheme, zero is encoded UPC (Universal Product Code) - is a barcode symbology that is as 11 in decimal, or in POSTNET "binary" as 11000.) widely used worldwide for tracking trade items in stores. UPC (technically refers to UPC-A) consists of 12 numeric digits that are uniquely assigned to each trade item.  POSTNET Bar Code Encoding Table: QR Code Design: A QR code is detected by a 2-dimensional digital image sensor and then digitally analyzed by a programmed processor. The processor locates the three distinctive squares at the corners of the QR code image, using a smaller square (or multiple squares) near the fourth corner to normalize the image for size, orientation, and angle of viewing. The small dots throughout the QR code are then converted to binary numbers and validated with an error-correcting algorithm. QR Code Composition/Structure: POSTNET Bar Code Formats: A 5 digit (plus check digit) barcode, containing the basic ZIP Code only, referred to as the "A" code. 32 bars total. A 6 digit (plus check digit) barcode, containing the last 2 digits of the ZIP Code and the 4 digits of the ZIP+4 Code, referred to Positioning Detection Markers as a "B" code. 37 bars total. Located at three corners of each A 9 digit (plus check digit) barcode, containing the ZIP Code code, it allows a scanner to and ZIP+4 Code, referred to as the "C" code. 52 bars total. accurately recognize the Code and An 11 digit (plus check digit) barcode, containing the ZIP read it at high speed, while Code, ZIP+4 Code, and the delivery point code. indicating the direction in which POSTNET Bar Code Sample: the Code is printed. They essentially help quickly identify the presence of a QR Code in an image and it's orientation. Alignment Markings Smaller than the position detection markers, they help straighten out QR Codes drawn on a curved surface. QR (Quick Response) Code And, the more information a Code It is a type of matrix barcode (or two-dimensional barcode) stores, the larger it is and the more invented in 1994 by Masahiro Hara in the Japanese automotive alignment patterns it requires. company Denso Wave. Timing Pattern A QR code uses four standardized encoding modes (numeric, Alternating black/white modules alphanumeric, byte/binary, and kanji) to store data efficiently; on the QR Code with the idea of extensions may also be used. accurately helping configure the The Quick Response system became popular outside the data grid. automotive industry due to its fast readability and greater Using these lines, the scanner storage capacity compared to standard UPC barcodes. determines how large the data Applications include product tracking, item identification, time matrix is. tracking, document management, and general marketing. Version Information A QR code consists of black squares arranged in a square grid on a white background, which can be read by an imaging Specifies the version number. device such as a camera, and processed using Reed–Solomon error correction until the image can be appropriately There are 40 different QR Code interpreted. versions, these markers specify the one that is being used. The most The required data is then extracted from patterns that are common ones are versions 1 to 7. present in both horizontal and vertical components of the image. Format Information QR codes may be used to display text to the user, to open a The format patterns contain webpage on the user's device, to add a vCard contact to the information about the error user's device, to open a Uniform Resource Identifier (URI), to tolerance and the data mask connect to a wireless network, or to compose an email or text pattern and make it easier to scan message. the Code.  Data and Error Correction Keys Dynamic It allows you to update, edit and change the type of the QR It is where all the data is contained, Code however many times you need, which makes them the also sharing the space with the best fit for business and marketing purposes. error correction blocks that allow up to 30% of the Code to be Static QR Codes Sample: damaged. Quiet Zone This is similar to the importance of white space in design. It offers structure and improves comprehension. Used by the scanning program in Dynamic QR Codes Sample: order to distinguish the QR Code from its surroundings. QR Code Sample Code Symbols: BINARY CODED DECIMAL - BCD CODE It is a class of binary encodings of decimal numbers where each digit is represented by a fixed number of bits, usually four or eight. This is also called "8421" encoding, Simple Binary Coded Decimal (SBCD) QR Code Versions: BCD Application: BCD was used in many early decimal computers, and is implemented in the instruction set of machines such as the IBM System/360 series and its descendants, Digital Equipment Corporation's VAX, the Burroughs B1700, and the Motorola 68000-series processors. M3: Serial Data Transmission Serial Data Transmission Information is transmitted in bits/bytes. One communication link/channel is used. Usually a pair of wires for the transmit and receive. Slow compared to parallel transmission. (early implementation). Less cost compared to parallel transmission due to the wires needed. Types of QR Codes: Used for short or long distance communication. Static The interfaces used by the computers are called COM ports. It contains information that is fixed and uneditable once the (Communication Ports). Code has been generated. They are great for personal use and Implemented in serial port (COM) or USB ports. for QR Code API, a key to creating large batches of Codes for In order to connect the DTE to DCE serial interfaces (cables) employee IDs, event badges, technical product are utilized. This has been the common practice in order to documentation, and much more. transmit data in a serial transmission medium such as a telecommunication line.  Serial Interfaces are also used to connect a computer to a The V.24 or EIA/TIA RS232 Interface Electrical Specifications microcontroller device. Defines the signaling between the DTE and the DCE. In wireless communications, serial interfaces will not be utilized as main transport for data, examples are the WIFI and The convention specifies a binary signal (data), that with WIMAX connections. respect to ground, a voltage more negative than -3V is interpreted as binary 1 and a voltage more positive than +3V is interpreted as binary 0. For control signals, a voltage more negative than -3V is interpreted as an OFF condition and a voltage more positive than +3V is interpreted as an ON condition. The standard specifies a maximum open-circuit voltage of 25 volts: signal levels of ±5 V, ±10 V, ±12 V, and ±15V are all commonly seen depending on the voltages available to the line driver circuit. There are 4 functional specifications namely- the data, control, timing and ground. There is one primary data circuit in each direction for full duplex operation. The secondary data circuits are used for half duplex operation. There are 15 control circuits, 3 timing circuits and 1 ground. Four Characteristics of Serial Interfaces Mechanical - pertains to the actual physical connection of the DTE to DCE. Typically the signal and control interchange circuits are bundled into a cable with a terminator plug, male or female on each end. Electrical - it specifies the voltage levels and the timing of the voltage changes. Both the DTE and DCE must use the same voltage levels to mean the same things and must use the same duration of the signal elements. Functional - specifies the data, control, timing and electrical ground signals. Procedural - specifies the sequence of events for transmitting data based on the functional characteristics of the interface. Serial Interface Standard RS 232 The V.24 or EIA/TIA RS232 Interface The most widely used serial interface. It was first issued by EIA (Electronics Industries Association) in 1962. The standard covers the following aspects: The V.24 or EIA/TIA RS232 Procedural Specifications Mechanical: ISO2110 Dial Up Half Duplex Procedure: Electrical: V.28 When a call is made ,the telephone sends a ringing signal. Functional: V.24 Procedural: V.24 A modem will respond by asserting the Ring Indicator and the DTE answers by asserting the Data Terminal Ready and at the same time asserts the Carrier Detect. If there is no carrier the call will be dropped.  Serial Interface Standard V.35 V.35 Cable Standard V.35 is a high-speed serial interface designed to support both higher data rates and connectivity between DTEs data- terminal equipment) or DCEs (data-communication equipment) over digital lines. V.35 is a partially balanced, partially single-ended interface specification. The data leads and clock leads are balanced, the handshake leads are single-ended. Most commonly used for 56kbps and 64kbps data rates. (early implementation) As it evolves, much higher rates are possible [ ISDN (64 or 128Kbps), FractionalT1 128 Kbps to 1.544MbpsT1, ATM and Frame Relay]. V.35 cable distances theoretically can range up to 4000 feet (1200 m) at speeds up to 100 Kbps. Actual distances will depend on your equipment and the quality of the cable. Lan routers often come equipped with a V.35 electrical interface but many today are using a HSSI interface at speeds higher than T1 and above (typicalT3 45 Mbps).  V.35 Cable Standard Pin Assignments and Voltages Examples of peripherals that are connected via USB include computer keyboards and mice, video cameras, printers, portable media players, mobile (portable) digital telephones, disk drives, and network adapters. USB connectors have been increasingly replacing other types as charging cables of portable devices. A group of seven companies began the development of USB in 1995: Compaq, DEC, IBM, Intel, Microsoft, NEC, and Nortel. The goal was to make it fundamentally easier to connect external devices to PCs by replacing the multitude of connectors at the back of PCs, addressing the usability issues of existing interfaces, and simplifying software configuration Transmitter output voltage from a balanced transmitter of all devices connected to USB, as well as permitting greater indicating a MARK is +0.35Vdc for the B line, -0.2Vdc for the A data transfer rates for external devices and Plug and Play line. features. Indication of a SPACE condition is +0.35Vdc for the A line, - Universal Serial Bus Versions 0.2Vdc for the B line. Output voltage difference is 0.55Vdc. To make sense to the receiver it must be at least 0.01Vdc USB 1.X – Released in January 1996, USB 1.0 specified difference between the A line and B line. signaling rates of 1.5 Mbit/s (Low Bandwidth or Low V.35 Cable Wire Map Speed) and 12 Mbit/s (Full Speed). It did not allow for extension cables or pass-through monitors, due to timing and power limitations. Few USB devices made it to the market until USB 1.1 was released in August 1998. USB 1.1 was the earliest revision that was widely adopted and led to what Microsoft designated the "Legacy-free PC". USB 2.0 – It was released in April 2000, adding a higher maximum signaling rate of 480 Mbit/s (maximum theoretical data throughput 53 MByte/s), named High Speed or High Bandwidth, in addition to the USB 1.x Full Speed signaling rate V.35 Cable Sample Connection of 12 Mbit/s (maximum theoretical data throughput 1.2 MByte/s). USB 3.x – The specification was released on 12 November 2008, with its management transferring from USB 3.0 Promoter Group to the USB Implementers Forum (USB-IF) and announced on 17 November 2008 at the SuperSpeed USB Developers Conference. USB 3.0 adds a SuperSpeed transfer mode, with associated backward compatible plugs, receptacles, and cables. SuperSpeed plugs and receptacles are identified with a distinct logo and blue inserts in standard format receptacles. The SuperSpeed bus provides for a transfer mode at a nominal rate of 5.0 Gbit/s, in addition to the three existing transfer modes. Its efficiency is dependent on a number of factors including physical symbol encoding and link level overhead. The SuperSpeed bus provides for a transfer mode at a nominal rate of 5.0 Gbit/s, in addition to the three existing transfer Universal Serial Bus Standard modes. Its efficiency is dependent on a number of factors Universal Serial Bus (USB) is an industry standard that including physical symbol encoding and link level overhead. establishes specifications for cables, connectors and protocols At a 5 Gbit/s signaling rate with 8b/10b encoding, each byte for connection, communication, and power supply needs 10 bits to transmit, so the raw throughput is 500 MB/s. (interfacing) between computers, peripherals and other When flow control, packet framing and protocol overhead are computers. considered, it is realistic for 400 MB/s (3.2 Gbit/s) or more to First released in 1996, the USB standards are maintained by transmit to an application. Communication is full-duplex in the USB Implementers Forum (USB-IF). The four generations SuperSpeed transfer mode; earlier modes are half-duplex, of USB are: USB 1.x, USB 2.0, USB 3.x, and USB4. arbitrated by the host. USB was designed to standardize the connection of peripherals USB 3.1 – It was released in July 2013 has two variants. to personal computers, both to communicate with and to The first one preserves USB 3.0's SuperSpeed transfer mode supply electric power. and is labeled USB 3.1 Gen 1, and the second version introduces a new SuperSpeed+ transfer mode under the label It has largely replaced interfaces such as serial ports and of USB 3.1 Gen 2. SuperSpeed+ doubles the maximum data parallel ports and has become commonplace on a wide range signaling rate to 10 Gbit/s, while reducing line encoding of devices.  overhead to just 3% by changing the encoding scheme to represent the receptacle, though these uses are inconsistent 128b/132b. with established definitions of connector gender. USB 3.2 – It was released in September 2017, preserves existing USB 3.1 SuperSpeed and SuperSpeed+ data modes but introduces two new SuperSpeed+ transfer modes over the USB-C connector with data rates of 10 and 20 Gbit/s (1.25 and 2.5 GB/s). The increase in bandwidth is a result of multi-lane operation over existing wires that were intended for flipflop capabilities of the USB-C connector. USB 4 – It was released on 29 August 2019 by the USB Implementers Forum. USB4 is based on the Thunderbolt 3 protocol. It supports 40 Gbit/s throughput, is compatible with Thunderbolt 3, and backward compatible with USB 3.2 and USB 2.0. The architecture defines a method to share a single highspeed link with multiple end device types dynamically that best serves the transfer of data by type and application. Naming Scheme for USB Version 3.2 Starting with the USB 3.2 standard, to help companies with branding of the different transfer modes, USB-IF recommended branding the 5, 10, and 20 Gbit/s transfer modes as SuperSpeed USB 5Gbps, SuperSpeed USB 10Gbps, and SuperSpeed USB 20Gbps, respectively Universal Serial Bus Pin Outs USB Type A and B USB Type-A is used to make a connection with a PC while Type B is used to connect smaller peripherals. In other words, Type A is a downstream connector, while Type B is an upstream connector. Signaling: Universal Serial Bus Connectors The three sizes of USB connectors are the default or standard USB Mini Type A and B format intended for desktop or portable equipment, the mini It’s a smaller version of Type A and B which was extensively intended for mobile equipment, which was deprecated when it was replaced by the thinner micro size, all of which were used with old mobile phones. The Mini B connector is more deprecated with the release of Type-C. popular than Mini A. USB Mini B is thinner and more compact than Mini A. Hence it is used for PDAs, digital cameras, etc. Unlike other data buses (such as Ethernet), USB connections Another significant development imposed on Type Mini is that are directed; a host device has "downstream" facing ports that it has an additional pin to support On-the-GO (OTG) connect to the "upstream" facing ports of devices. connection. Thus it has 5 pins. The pin connections are given in the table below Only downstream facing ports provide power; this topology was chosen to easily prevent electrical overloads and damaged equipment. Thus, USB cables have different ends: A and B, with different physical connectors for each. Each format has a plug and receptacle defined for each of the A and B ends. USB Micro Type A and B It is thinner and gives a higher data transfer speed than the USB Mini. It is often used for charging portable devices and comes in two shapes. Micro A is rectangular whereas Type Micro B has a camper shape. The USB Micro also has 5 pins The official USB specification documents also periodically similar to that of the USB Mini, where the additional pin define the term male to represent the plug, and female to supports OTG connectivity. USB 3.0/3.1 Type A and B USB Standard 3 is widely known as the SuperSpeed Mode that brought a revolution in USB manufacturing. It is capable of transferring data with a speed of 5Gbps and above. Since separate unidirectional paths are used to transmit and receive data, therefore it has larger bandwidth. USB Cable Types USB Micro B 3.0/3.1 The superspeed version of Micro USB was introduced to Type B. Apart from the existing structure, the five additional pins are placed as an extension. Thus, it has a wider structure. USB Bridge Cable A bridge cable is a special cable with a chip and active electronics in the middle of the cable. The chip in the middle USB Type C 3.0/3.1 of the cable acts as a peripheral to both computers, and allows for peer-to-peer communication between the computers. It supports data transmission as well as power delivery. And The USB bridge cables are used to transfer files between two thus, it has become a universal connector for modern devices. computers via their USB ports. The major attraction of Type C USB is that it is flippable. The pin connections at the top and bottom are similar so we don’t have to bother to insert the connector in the correct direction. USB Applications Device Classes The functionality of a USB device is defined by a class code sent to a USB host. This allows the host to load software modules for the device and to support new devices from different manufacturers.  Serial to Parallel Converter Sample Serial I/O Circuits USB Power Standards USB Battery Charging (BC) defines a charging port, which may be a charging downstream port (CDP), with data, or a dedicated charging port (DCP) without data. Dedicated charging ports can be found on USB power adapters to run attached devices and battery packs. Charging ports on a host with both kinds will be labeled. Serial Input/Output Interface Null Modem The commonly used term for the hardware serial interface inside the DTE are Asynchronous Communications Interface Null Modem is a communication method used to connect two Adaptor (ACIA) and Universal Asynchronous DTEs (computer, terminal, printer etc.) directly using an RS232 Receiver/Transmitter (UART) serial cable. ACIA - An integrated circuit that provides data formatting and The name stems from the historical use of the RS-232 cable to control to EIA-232 serial interfaces. connect two teleprinter devices to modems in order to communicate with one another. UART – An integrated circuit that transmit and receives serial data inside a DTE device. It is an RS-232 serial cable where the transmit and receive lines are crosslinked. In some cables there are also handshake lines Parallel to Serial Converter crosslinked. In many situations a straight-through serial cable is used, together with a null modem adapter. Null Modem Implementations RS 232 DB9 Null Modem with Full Handshaking V.35 Null Modem Setup Parallel Data Transmission More than one bit is transmitted at the same time. More than one communication link is used for transmission. Faster compared to serial data transmission. More costly compared to serial data transmission. Used for short distance communications. Example: parallel printer port (Centronics) of PCs, Data Bus inside the mainboard of the computer or microcontroller IEEE 1284 Parallel Printer Standard IEEE 1284 is a standard that defines bi-directional parallel communications between computers and other devices. It was originally developed in the 1970s by Centronics, and was widely known as the Centronics port, both before and after its IEEE standardization. IEEE 1284 Parallel Port Modes of Operation Compatibility Mode, also known as Centronics standard or SPP, is a uni-directional implementation with only a few differences from the original Centronics design. This mode is almost exclusively used for printers. Nibble Mode is an interface that allows the device to transmit data four bits (a nibble) at a time, (re)using four of the status lines of Compatibility Mode for data. Byte Mode, also known as "Bi-Directional" (although all modes except Compatibility Mode are in fact bidirectional), is a half-duplex mode that allows the device to transmit eight bits at a time using the same data lines that are used for the other direction. Enhanced Parallel Port (EPP) is a half-duplex bi-directional interface designed to allow devices like printers, scanners, or V.35 Null Modem Wiring Layout storage devices to transmit large amounts of data while quickly being able to switch channel direction. Extended Capability Port (ECP) is a half-duplex bidirectional interface similar to EPP, except that PC implementations use direct memory access (usually ISA DMA on channel 3) to provide even faster data transfer than EPP by having the ISA DMA hardware and the parallel port interface hardware handle the work of transferring the data instead of letting the CPU do this work IEEE 1284 Signals Breakout Box Output signals of the parallel port are defined as typical TTL It is a piece of electrical test equipment used to support logical level signals. High level is defined by voltage from 3.5V integration testing, expedite maintenance, and streamline the to 5.5V and low level from 0V to 0.4V troubleshooting process at the system, subsystem, and component-level by simplifying the access to test signals. A breakout box serves as a troubleshooting tool to determine the wiring of an electrical connector interface on a networking device or computer. Typically, a breakout box is inserted between two electrical devices to determine which signal or power interconnects are active. Monitoring devices are available for testing serial interfaces, including RS-232, RS-449, V.35, and X.21, as well as specialty interfaces. IEEE 1284 Parallel Printer Cable Pin Outs They generally come with several kinds of connectors and are quick and easy to use for isolating problems with serial transmission connections in networking, telecommunications, and industrial settings. The most common breakout boxes use D-subminiature connectors (sometimes referred to as D-sub connectors and sometimes erroneously as DB connectors) and are configured with both male and female DE-9, DA-15, DB-25, DC-37 or DD- 50 standard density connectors and related test points. These units can also be used to simulate special cables, interconnect RS-232 devices, or adapt test equipment to an RS-232 device. IEEE 1284 Parallel Printer Cable Connection Breakout Box Applications Breakout boxes for post-production studio editing suites. Breakout boxes (also called patch bays or patch panels) are used to patch audio/video output signals from multiple sources and connect them to other devices quickly. These boxes range from simple analog audio interconnects with up to 96 audio ins/outs to complex plug-in components with composite video, S-Video, HDMI, RS422 control, and digital signaling. Laplink Cable Industrial I/O breakout box. A piece of electronic test A null printer cable, used in connecting two computers using equipment used for diagnosing problems in computer printer ports to transfer files. communications, typically over a serial port. The breakout box sits between two pieces of equipment and usually has some LEDs to display the status of the different signals in the serial cable. It will also often have DIP switches to let the user connect or disconnect different signals in the cable. RS-232 breakout box: Typically, RS-232 breakout boxes offer complete control of the RS-232 interface, test, rewire, and open signal lines. These devices are pocket-sized for circuit Laplink Cable Wiring Layout testing, monitoring, and patching. They usually provide ten interface signal powered LEDs to permanently monitor TD, RD, RTS, CTS, DSR, CD, TC, RC, DTR (E) TC signals, as well as enabling the breakout of individual circuits or reconfiguration or patching any or all of the 24 active switch positions Personal computer sound cards. A DA15 connector on the outside of the board is often broken out into DIN connectors for MIDI. Some professional audio applications use rackmount breakout boxes. A patch panel can also function as a breakout box, in the case of multi-channel DB25 (or other) connectors used for multi-track recording. Docking stations for notebook computers. These draw the signal for multiple connectors from the pins of one connector. Electronic control units (ECUs) in automotive engines have proprietary connectors that are densely packed,  environmentally sealed, and difficult to gain access to without causing damage. The manufacturer sometimes provides a breakout box to allow service engineers to test the unit. M4: Data Synchronization Asynchronous Data Transmission Uses serial transmission Characters are transmitted and received one at a time. Sometimes called “start and stop” transmission. Start bit is always a binary 0. The logical status of the communication line when there is no data being transmitted is always a 1 (idle line ones). The 1 to 0 transition of the start bit activates a circuit at the receiver to check if a valid start bit has arrived. Stop bit is always a 1 (to make sure that there will be a 1 to 0 transition for the next start bit). Stop bit can be 1, 1.5 or 2 times the duration of an ordinary bit. Receiver clock is not synchronized with the transmitter clock. Frequencies of the transmitter and receiver clocks must be sufficiently close if not the same. (bit rate or baud rate Framing Error/Timing Error Example configuration must be the same). Otherwise, clock slippage For a data rate of 10,000 bits per second (10kbps) at the may occur. transmitter; each bit is 0.1ms or 100us in duration. If the transmit clock is substantially lower than the receive clock, underslipping occurs. The reverse causes overslipping. Assuming the receiver is off by 7% or 7us per bit time, the Framing characters individually with start and stop bits is receiver will now sample the incoming character by 93us. sometimes said to occur on a character by character basis. One byte at a time transmission with framed with start and With this set up, the last sample will be erroneous thus stop bits. framing error will occur. Two errors will be visible; incorrectly Relatively slow if a lot of data are to be transmitted received sample and out of alignment data. continuously. More efficient for short messages. Typically used with “dumb terminals” Examples of Asynchronous Data Transmission Modem data connections over telephone lines using start stop protocols (Z Modem, Kermit, Y Modem), Legacy Modem Communication, X.25 networks, Facsimile, teleprinters, ATM( Asynchronous Transfer Mode). While precise synchronism between transmitter and receiver Synchronous Data Transmission is not required, receiving station and transmitting station must have the same set up regarding: Uses serial data transmission. a) Number of bits for data Does not use start and stop bits. b) Transmission speed (bit rate) Usually uses start and ending flags. Framing error results when transmission speed for Receiver clock is synchronized with the transmitter clock. transmitter and receiver are not the same. This is because Usually, more than one character is transmitted in one data incorrect timing in the sampling of received data results block. Framing is the process of deciding which groups of 8 bits Relatively fast if a lot of data are to be transmitted constitute a character. – Use of parity checking (odd, even, continuously. disabled) Methods of Data Synchronization If the set up for parity are not the same, receiver could interpret that there was a Parity Error even if there was none. 1. Provide a separate clock between transmitter and receiver. Flow control procedure is used to prevent data loss due to One side (transmitter and receiver) pulses the line regularly insufficient memory used as buffer for received data. with one short pulse per bit time. The other side uses this Overrun error results when receiver buffer (temporary storage regular pulses as a clock. (Typically used for short distances). for received data) becomes full and additional data are stored in it while previously stored data have not yet been processed. 2. Embed the clocking information in the data signal. (long Data Overrun occurs when a character arrive and it cannot be distance). This is used in some encoding methods such as handled by the receiver. Manchester Encoding. In analog signals, the carrier frequency is used to synchronize the receiver based on the phase of the carrier. 3. Use of framing bytes. To determine the beginning and end of the data called frame, each frame has a preamble and  postamble. Preamble is a bit pattern at the beginning while a Isochronous Data Transmission postamble is a bit pattern at the end of the frame. Isochronous transmission transmits asynchronous data over a synchronous data link so that individual characters are only separated by a whole number of bit-length intervals. An isochronous message protocol assigns each data source a fixed amount of time to transmit (its "slot") within each cycle through the sources. That guarantees that each source will have regular opportunities to transmit the latest information. Isochronous communication suits applications where a steady data stream is more important than completeness and accuracy, e.g. video conference.ng, real time video and audio. Synchronous Data Transmission Protocols (streaming services) Bisync (Binary Synchronous) Examples: ATM (Asynchronous Transfer Mode) Network, High ○ developed by IBM. Performance Serial Bus. ○ Uses half duplex error control procedures Plesiochronous Data Transmission SDLC (Synchronous Data Link Control) ○ developed by IBM. Refers to the transmission where the sending and receiving ○ Uses full duplex error control procedures devices are synchronized but set to different clocks. The ○ relatively faster compared to Bisync different clocks can cause drifting phase or “sync slips”. In HDLC (High Level Data Link Control) order for the original data to be recovered, bit stuffing is used ○ Improvement SDLC and adopted as a standard to compensate for the timing difference. Example: PDH by multiple vendors (Plesiochronous Digital Hierarchy) – already obsolete and replaced by SDH. SDLC FRAME HDLC FRAME PPP FRAME PPPoE FRAME Synchronous Data Transmission Examples SONETs (Synchronous Optical Network) and SDH (Synchronous Digital Hierarchy) Networks. T and E carrier networks using Synchronous WAN Protocols like HDLC, PPP, PPPoE.