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Those modems are obsolete, having been replaced by modems which convert asynchronous data to synchronous forms, but similar synchronous telecommunications protocols survive in numerous block-oriented technologies such as the widely used IEEE 802.2 (Ethernet) link-level protocol. USARTs are still sometimes integrated with MCUs.
Example of a UART frame. In this diagram, one byte is sent, consisting of a start bit, followed by eight data bits (D1-8), and two stop bits, for a 11-bit UART frame. The number of data and formatting 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 ...
For example, the UART-based FlexWire protocol begins each frame with a 'U' (0x55) sync byte. FlexWire receivers use the sync byte to precisely set their UART bit-clock frequency without a high-precision oscillator. [4] For example, the Ethernet preamble contains 56 bits of alternating 1 and 0 bits for synchronizing bit clocks.
Byte-oriented framing protocol is "a communications protocol in which full bytes are used as control codes. Also known as character-oriented protocol." [1] For example UART communication is byte-oriented. The term "character-oriented" is deprecated, [by whom?] since the notion of character has changed. An ASCII character fits to one byte (octet ...
The 16550 UART (universal asynchronous receiver-transmitter) is an integrated circuit designed for implementing the interface for serial communications. The corrected -A version was released in 1987 by National Semiconductor . [ 1 ]
The 8250 UART was used in several 8-bit computers at least since 1978. IBM used the 8250 UART in the IBM PC (1981). The 8250A and 8250B revisions were later released, and the 16450 was introduced with the IBM Personal Computer/AT (1984). The main difference between releases was the maximum communication speed. [4]
A packet-switched network transmits data that is divided into units called packets.A packet comprises a header (which describes the packet) and a payload (the data). The Internet is a packet-switched network, and most of the protocols in this list are designed for its protocol stack, the IP protocol suite.
For example, one may imagine a computer sending data to a slow printer. Since the computer is faster at sending data than the printer can print it, the printer falls behind and approaches a situation where it would be overwhelmed by the data. The printer reacts to this situation by sending XOFF to the computer, which temporarily stops sending data.