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A universal asynchronous receiver/transmitter, abbreviated UART , is a computer hardware device that translates data between parallel and serial forms. UARTs are commonly used in conjunction with communication standards such as TIA (formerly EIA) RS-232, RS-422 or RS-485. The ''universal'' designation indicates that the data format and transmission speeds are configurable. The electric signaling levels and methods (such as differential signaling etc.) are handled by a driver circuit external to the UART. A UART is usually an individual (or part of an) integrated circuit (IC) used for serial communications over a computer or peripheral device serial port. UARTs are now commonly included in microcontrollers. A dual UART, or ''DUART'', combines two UARTs into a single chip. An octal UART or ''OCTART'' combines eight UARTs into one package, such as the Exar XR16L788 or the NXP SCC2698. Many modern ICs now come with a UART that can also communicate synchronously; these devices are called ''USARTs'' (universal synchronous/asynchronous receiver/transmitter). ==Transmitting and receiving serial data== The universal asynchronous receiver/transmitter (UART) takes bytes of data and transmits the individual bits in a sequential fashion.〔Adam Osborne, ''An Introduction to Microcomputers Volume 1: Basic Concepts'', Osborne-McGraw Hill Berkeley California USA, 1980 ISBN 0-931988-34-9 pp. 116-126〕 At the destination, a second UART re-assembles the bits into complete bytes. Each UART contains a shift register, which is the fundamental method of conversion between serial and parallel forms. Serial transmission of digital information (bits) through a single wire or other medium is less costly than parallel transmission through multiple wires. The UART usually does not directly generate or receive the external signals used between different items of equipment. Separate interface devices are used to convert the logic level signals of the UART to and from the external signalling levels. External signals may be of many different forms. Examples of standards for voltage signaling are RS-232, RS-422 and RS-485 from the EIA. Historically, current (in current loops) was used in telegraph circuits. Some signaling schemes do not use electrical wires. Examples of such are optical fiber, IrDA (infrared), and (wireless) Bluetooth in its Serial Port Profile (SPP). Some signaling schemes use modulation of a carrier signal (with or without wires). Examples are modulation of audio signals with phone line modems, RF modulation with data radios, and the (DC-LIN ) for power line communication. Communication may be ''simplex'' (in one direction only, with no provision for the receiving device to send information back to the transmitting device), ''full duplex'' (both devices send and receive at the same time) or ''half duplex'' (devices take turns transmitting and receiving). 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Universal asynchronous receiver/transmitter」の詳細全文を読む スポンサード リンク
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