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In telecommunications, asynchronous communication is transmission of data, generally without the use of an external clock signal, where data can be transmitted intermittently rather than in a steady stream. Any timing required to recover data from the communication symbols is encoded within the symbols.
In computing and telecommunication, a control character or non-printing character (NPC) is a code point in a character set, that does not represent a written symbol. They are used as in-band signaling to cause effects other than the addition of a symbol to the text. All other characters are mainly printing, printable, or graphic characters, except perhaps for the "space" character.
In telecommunication, an end-of-Transmission character (EOT) is a transmission control character. Its intended use is to indicate the conclusion of a transmission that may have included one or more texts and any associated message headings.
In telecommunication, a non-return-to-zero (NRZ) line code is a binary code in which ones are represented by one significant condition, usually a positive voltage, while zeros are represented by some other significant condition, usually a negative voltage, with no other neutral or rest condition.
A universal asynchronous receiver-transmitter is a computer hardware device for asynchronous serial communication in which the data format and transmission speeds are configurable. It sends data bits one by one, from the least significant to the most significant, framed by start and stop bits so that precise timing is handled by the communication channel. The electric signaling levels are handled by a driver circuit external to the UART. Two common signal levels are RS-232, a 12-volt system, and RS-485, a 5-volt system.
High-Level Data Link Control (HDLC) is a bit-oriented code-transparent synchronous data link layer protocol developed by the International Organization for Standardization (ISO). The standard for HDLC is ISO/IEC 13239:2002.
Asynchronous serial communication is a form of serial communication in which the communicating endpoints' interfaces are not continuously synchronized by a common clock signal. Instead of a common synchronization signal, the data stream contains synchronization information in form of start and stop signals, before and after each unit of transmission, respectively. The start signal prepares the receiver for arrival of data and the stop signal resets its state to enable triggering of a new sequence.
Synchronous Data Link Control (SDLC) is a computer communications protocol. It is the layer 2 protocol for IBM's Systems Network Architecture (SNA). SDLC supports multipoint links as well as error correction. It also runs under the assumption that an SNA header is present after the SDLC header. SDLC was mainly used by IBM mainframe and midrange systems; however, implementations exist on many platforms from many vendors. The use of SDLC is becoming more and more rare, mostly replaced by IP-based protocols or being tunneled through IP. In the United States, SDLC can be found in traffic control cabinets.
In telecommunications, 8b/10b is a line code that maps 8-bit words to 10-bit symbols to achieve DC-balance and bounded disparity, and at the same time provide enough state changes to allow reasonable clock recovery. This means that the difference between the counts of ones and zeros in a string of at least 20 bits is no more than two, and that there are not more than five ones or zeros in a row. This helps to reduce the demand for the lower bandwidth limit of the channel necessary to transfer the signal.
XMODEM is a simple file transfer protocol developed as a quick hack by Ward Christensen for use in his 1977 MODEM.ASM terminal program. It allowed users to transmit files between their computers when both sides used MODEM. Keith Petersen made a minor update to always turn on "quiet mode", and called the result XMODEM.
A universal synchronous and asynchronous receiver-transmitter (USART) is a type of a serial interface device that can be programmed to communicate asynchronously or synchronously. See universal asynchronous receiver-transmitter (UART) for a discussion of the asynchronous capabilities of these devices.
IEEE Standard 1355-1995, IEC 14575, or ISO 14575 is a data communications standard for Heterogeneous Interconnect (HIC).
Binary Synchronous Communication is an IBM character-oriented, half-duplex link protocol, announced in 1967 after the introduction of System/360. It replaced the synchronous transmit-receive (STR) protocol used with second generation computers. The intent was that common link management rules could be used with three different character encodings for messages. Six-bit Transcode looked backwards to older systems; USASCII with 128 characters and EBCDIC with 256 characters looked forward. Transcode disappeared very quickly but the EBCDIC and USASCII dialects of Bisync continued in use.
Synchronous Idle (SYN) is the ASCII control character 22 (0x16), represented as ^V in caret notation. In EBCDIC the corresponding character is 50 (0x32). Synchronous Idle is used in some synchronous serial communication systems such as Teletype machines or the Binary Synchronous (Bisync) protocol to provide a signal from which synchronous correction may be achieved between data terminal equipment, particularly when no other character is being transmitted.
ISO 1745:1975 Information processing – Basic mode control procedures for data communication systems is an early ISO standard defining a Telex-oriented communications protocol that used the non-printable ASCII transmission control characters SOH, STX, ETX, EOT, ENQ (Enquiry), ACK (Acknowledge), DLE, NAK, SYN, and ETB.
In data networking, telecommunications, and computer buses, an acknowledgment (ACK) is a signal that is passed between communicating processes, computers, or devices to signify acknowledgment, or receipt of message, as part of a communications protocol. The negative-acknowledgment is a signal that is sent to reject a previously received message or to indicate some kind of error. Acknowledgments and negative acknowledgments inform a sender of the receiver's state so that it can adjust its own state accordingly.
270x is a generic name for a family of IBM non-programmable communications controllers used with System/360 and System/370 computers.
The IBM 7701 Magnetic Tape Transmission Terminal was a communications device announced by IBM in 1960. It was designed to transfer the contents of a reel of magnetic tape over a leased or dial telephone circuit.
Synchronous serial communication describes a serial communication protocol in which "data is sent in a continuous stream at constant rate."
The Hazeltine 1500 was a popular smart terminal introduced by Hazeltine Corporation in April 1977 at a price of $1,125. Using a microprocessor and semiconductor random access memory, it implemented the basic features of the earlier Hazeltine 2000 in a much smaller and less expensive system. It came to market just as the microcomputer revolution was taking off, and the 1500 was very popular among early hobbyist users.
References
- 1 2 3 IBM Corporation (1972). IBM 1130 Functional Characteristics (PDF). pp. 171–172.
- ↑ IBM Corporation (1961). Reference Manual IBM 7701 Magnetic Tape Transmission Terminal (PDF). p. 8.