EN 61158-4-2:2012

IEC 61158-4-2:2010(E) describes the protocol that provides communication opportunities to all participating data-link entities, sequentially and in a cyclic synchronous manner. Foreground scheduled access is available for time-critical activities together with background unscheduled access for less critical activities. Deterministic and synchronized transfers can be provided at cyclic intervals up to 1 ms and device separations of 25 km. This performance is adjustable dynamically and on-line by re-configuring the parameters of the local link whilst normal operation continues. By similar means, DL connections and new devices may be added or removed during normal operation. This protocol provides means to maintain clock synchronization across an extended link with a precision better than 10 s. This second edition cancels and replaces the first edition published in 2007 and constitutes a technical revision. The main changes with respect to the previous edition are: -Clause 2 and Bibliography: update of normative and bibliographic references; - subclause 3.5: update of abbreviations; - subclause 7.6: updates of the Ethernet Link object; - subclause 7.7: minor update of the Devicenet object (additional attribute); - new subclauses 7.9 and 7.10: new DLR and QoS objects; - new Clause 10: new DLR protocol.