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In telecommunication and data transmission, serial communication is the process of sending data one bit at a time, sequentially, over a communication channel or computer bus. This is in contrast to parallel communication , where several bits are sent as a whole, on a link with several parallel channels.
(the START bit), waits 'half a bit duration' and then reads the value of the signal. A further delay of one 'whole bit duration' is executed before the next data bit is 'read' - repeating for the length of the whole serial word (typically 7/8-data bits). An optional PARITY bit follows the data bits and precedes the stop bit(s).
In data transmission, parallel communication is a method of conveying multiple binary digits simultaneously using multiple conductors. This contrasts with serial communication , which conveys only a single bit at a time; this distinction is one way of characterizing a communications link .
The last data bit is sometimes used as a parity bit. The number of data and formatting bits, the order of data bits, the presence or absence of a parity bit, the form of parity (even or odd) and the transmission speed must be pre-agreed by the communicating parties. The "stop bit" is actually a "stop period"; the stop period of the transmitter ...
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 following protocols were designed for serial communication, mostly for the RS-232 standard. They are used for uploading and downloading computer files via modem or serial cable (e.g., by null modem or direct cable connection). UUCP is one protocol that can operate with either RS-232 or the Transmission Control Protocol as its transport.
While specific examples follow, countless other connectors have been used for RS-232 connections. The 9-pin DE-9 connector has been used by most IBM-compatible PCs since the Serial/Parallel Adapter option for the PC-AT, where the 9-pin connector allowed a serial and parallel port to fit on the same card. [4]
Synchronous serial communication describes a serial communication protocol in which "data is sent in a continuous stream at constant rate." [1]Synchronous communication requires that the clocks in the transmitting and receiving devices are synchronized – running at the same rate – so the receiver can sample the signal at the same time intervals used by the transmitter.