FireWire vs USB comparison. FireWire (IEEE 1394) and USB (Universal Serial Bus) are both standards for communication between electronic devices. FireWire is the brand.

Data Communications Basics . Strangio(Developer of CAMI Research's Cable.

Eye continuity & hipot Cable & Harness test systems)Copyright . Synchronous Transmission. The ASCII Character Set.

Parity and Checksums. Data Compression.

Tabtight professional, free when you need it, VPN service. Ftdi Usb Serial Converter Drivers Uninstall. Communication. Information on communication protocols often used to talk with other devices. Please refer to Interfacing with Software for information on linking with. A go-to guide referred to by millions - by C. Strangio, developer of CAMI Research's CableEye continuity & hipot Cable & Harness test systems. Linux Network Configuration Networking, set-up and administration. This Linux tutorial covers TCP/IP networking, network administration and system configuration basics.

Data Encryption. Data Storage Technology. Data Transfer in Digital Circuits. Transmission over Short Distances (< 2 feet)Noise and Electrical Distortion. Transmission over Medium Distances (< 2.

Transmission over Long Distances (< 4. Transmission over Very Long Distances (> 4. Back to home page: Cable.

Eye Continuity & Hi. Pot Cable & Harness Test Systems. What is Data Communications? Next Topic . Over such small distances, digital data may be transmitted as direct, two- level electrical signals over simple copper conductors. Except for the fastest computers, circuit designers are not very concerned about the shape of the conductor or the analog characteristics of signal transmission. Frequently, however, data must be sent beyond the local circuitry that constitutes a computer. In many cases, the distances involved may be enormous.

Unfortunately, as the distance between the source of a message and its destination increases, accurate transmission becomes increasingly difficult. This results from the electrical distortion of signals traveling through long conductors, and from noise added to the signal as it propagates through a transmission medium. Although some precautions must be taken for data exchange within a computer, the biggest problems occur when data is transferred to devices outside the computer's circuitry. In this case, distortion and noise can become so severe that information is lost. Data Communications concerns the transmission of digital messages to devices external to the message source. As a rule, the maximum permissible transmission rate of a message is directly proportional to signal power, and inversely proportional to channel noise.

It is the aim of any communications system to provide the highest possible transmission rate at the lowest possible power and with the least possible noise. Communications Channels. Next Topic . It may be defined by a physical wire that connects communicating devices, or by a radio, laser, or other radiated energy source that has no obvious physical presence. Information sent through a communications channel has a source from which the information originates, and a destination to which the information is delivered.

Although information originates from a single source, there may be more than one destination, depending upon how many receive stations are linked to the channel and how much energy the transmitted signal possesses. In a digital communications channel, the information is represented by individual data bits, which may be encapsulated into multibit message units. A byte, which consists of eight bits, is an example of a message unit that may be conveyed through a digital communications channel. A collection of bytes may itself be grouped into a frame or other higher- level message unit. Divx Plus Player Codec Update Checker. Such multiple levels of encapsulation facilitate the handling of messages in a complex data communications network. Any communications channel has a direction associated with it: The message source is the transmitter, and the destination is the receiver. A channel whose direction of transmission is unchanging is referred to as a simplex channel.

For example, a radio station is a simplex channel because it always transmits the signal to its listeners and never allows them to transmit back. A half- duplex channel is a single physical channel in which the direction may be reversed.

Messages may flow in two directions, but never at the same time, in a half- duplex system. In a telephone call, one party speaks while the other listens. After a pause, the other party speaks and the first party listens. Speaking simultaneously results in garbled sound that cannot be understood. A full- duplex channel allows simultaneous message exchange in both directions. It really consists of two simplex channels, a forward channel and a reverse channel, linking the same points.

The transmission rate of the reverse channel may be slower if it is used only for flow control of the forward channel. Serial Communications. Next Topic . Because it is neither practical nor economic to transfer all bits of a long message simultaneously, the message is broken into smaller parts and transmitted sequentially. Bit- serial transmission conveys a message one bit at a time through a channel.

Each bit represents a part of the message. The individual bits are then reassembled at the destination to compose the message.

In general, one channel will pass only one bit at a time. Thus, bit- serial transmission is necessary in data communications if only a single channel is available.

Bit- serial transmission is normally just called serial transmission and is the chosen communications method in many computer peripherals. Byte- serial transmission conveys eight bits at a time through eight parallel channels.

Although the raw transfer rate is eight times faster than in bit- serial transmission, eight channels are needed, and the cost may be as much as eight times higher to transmit the message. When distances are short, it may nonetheless be both feasible and economic to use parallel channels in return for high data rates.

The popular Centronics printer interface is a case where byte- serial transmission is used. As another example, it is common practice to use a 1. On the other hand, when communicating with a timesharing system over a modem, only a single channel is available, and bit- serial transmission is required.

This figure illustrates these ideas: The baud rate refers to the signalling rate at which data is sent through a channel and is measured in electrical transitions per second. In the EIA2. 32 serial interface standard, one signal transition, at most, occurs per bit, and the baud rate and bit rate are identical. In this case, a rate of 9. If two electrical transitions were required for each bit, as is the case in non- return- to- zero coding, then at a rate of 9. The channel efficiency is the number of bits of useful information passed through the channel per second. It does not include framing, formatting, and error detecting bits that may be added to the information bits before a message is transmitted, and will always be less than one.

The data rate of a channel is often specified by its bit rate (often thought erroneously to be the same as baud rate). However, an equivalent measure channel capacity is bandwidth. In general, the maximum data rate a channel can support is directly proportional to the channel's bandwidth and inversely proportional to the channel's noise level. A communications protocol is an agreed- upon convention that defines the order and meaning of bits in a serial transmission.

It may also specify a procedure for exchanging messages. A protocol will define how many data bits compose a message unit, the framing and formatting bits, any error- detecting bits that may be added, and other information that governs control of the communications hardware. Channel efficiency is determined by the protocol design rather than by digital hardware considerations. Note that there is a tradeoff between channel efficiency and reliability - protocols that provide greater immunity to noise by adding error- detecting and - correcting codes must necessarily become less efficient. Asynchronous vs. Synchronous Transmission. Next Topic . Instead, there is usually a burst of regularly spaced binary data bits followed by a pause, after which the data flow resumes. Packets of binary data are sent in this manner, possibly with variable- length pauses between packets, until the message has been fully transmitted.

In order for the receiving end to know the proper moment to read individual binary bits from the channel, it must know exactly when a packet begins and how much time elapses between bits.