Editing Synchronous serial communication (section)

==Bit-oriented protocols==
[[Bit-oriented protocol]]s are synchronous protocols that view the transmitted data as a stream of bits with no semantics, or meaning. Control codes are defined in terms of bit sequences instead of characters.  Synchronization is maintained on an idle line by transmitting a predefined sequence of bits.  ''[[Synchronous Data Link Control]]'' (SDLC) specifies that a station continue transmitting a sequence of '1' bits on an idle line.<ref>{{cite book|last=IBM Corporation|title=IBM Synchronous Data Link Control General Information .|year=1979|url=http://bitsavers.informatik.uni-stuttgart.de/pdf/ibm/datacomm/GA27-3093-2_SDLC_General_Information_Mar79.pdf}}</ref> Data to be transmitted on an idle line is prefixed with a special bit sequence '01111110'b, called a ''flag''. SDLC was the first bit-oriented protocol developed, and it was later adopted by the [[International Organization for Standardization]] (ISO) as ''[[High-Level Data Link Control]]'' (HDLC).  Other examples of bit-oriented protocols are ''Logical Link Control'' (LLC)&mdash;[[IEEE 802.2]], and ANSI ''[[Advanced Data Communication Control Procedures]]'' (ADCCP).