ECMA-89

For the purpose of compatible interconnection of Data Processing equipment via a local area network using the token-passing ring access method, this ECMA Standard:

– Defines the frame format, including delimiters, addressing, and frame check sequence, and introduces timers, frame count, and priority stacks (see clause 3).

– Defines the medium access control protocol. The finite-state machine and state tables are supplemented with a prose description of the algorithms (see clause 4).

– Describes the services provided by the medium access control sublayer to the network management and LLC sublayer and the services provided by the Physical Layer to Network
Management and the medium access control sublayer. These services are defined in terms of service primitives and associated parameters (see clause 5).

– Defines the Physical Layer functions of symbol encoding and decoding, symbol timing and latency buffering (see clause 6).

– Defines the 1-and 4-megabit per second, shielded twisted pair attachment of the DTE to the medium including the definition of the medium interface connector (see clause 7).

A particular emphasis of this Standard is to specify the homogeneous externally visible characteristics needed for interconnection compatibility, while avoiding unnecessary constraints upon and changes to internal design and implementation of the heterogeneous processing equipment to be interconnected.