Site home page
Get alerts when Linktionary is updated
Book updates and addendums
Get info about the Encyclopedia of Networking and Telecommunicatons, 3rd edition (2001)
Download the electronic version of the Encyclopedia of Networking, 2nd edition (1996). It's free!
Contribute to this site
Electronic licensing info
BISYNC (Binary Synchronous Communications)
Note: Many topics at this site are reduced versions of the text in "The Encyclopedia of Networking and Telecommunications." Search results will not be as extensive as a search of the book's CD-ROM.
Binary synchronous communications, or BISYNC, is a character (byte)-oriented form of communication developed by IBM in the 1960s. It was originally designed for batch transmissions between the IBM S/360 mainframe family and IBM 2780 and 3780 terminals. It supports online and RJE (remote job entry) terminals in the CICS/VSE (Customer Information Control System/Virtual Storage Extended) environment.
BISYNC establishes rules for transmitting binary-coded data between a terminal and a host computer's BISYNC port. While BISYNC is a half-duplex protocol, it will synchronize in both directions on a full-duplex channel. BISYNC supports both point-to-point (over leased or dial-up lines) and multipoint transmissions. Each message must be acknowledged, adding to its overhead.
BISYNC is character oriented, meaning that groups of bits (bytes) are the main elements of transmission, rather than a stream of bits. The BISYNC frame is pictured next. It starts with two sync characters that the receiver and transmitter use for synchronizing. This is followed by a start of header (SOH) command, and then the header. Following this are the start of text (STX) command and the text. Finally, an end of text (EOT) command and a cyclic redundancy check (CRC) end the frame. The CRC provides error detection and correction.
Most of the bisynchronous protocols, of which there are many, provide only half-duplex transmission and require an acknowledgment for every block of transmitted data. Some do provide full-duplex transmission and bit-oriented operation.
BISYNC has largely been replaced by the more powerful SDLC (Synchronous Data Link Control).
Copyright (c) 2001 Tom Sheldon and Big Sur Multimedia.