EN 61158-4-7:2008

FOREWORD
INTRODUCTION
1 Scope
2 Normative references
3 Terms, definitions, symbols and abbreviations
4 Overview of the DL-protocol
5 General structure and encoding of PhIDUs and DLPDUs
  and related elements of procedure
6 DLPDU-specific structure, encoding and element of
  procedure
7 DL-service elements of procedure, interfaces and
  conformance
Annex A (informative) - Exemplary FCS implementation
Annex B (informative) - Object modeling
Annex C (informative) - Topology of multi-segment
        DL-subnetwork
Annex D (informative) - Management of transmission errors
Bibliography
Annex ZA (normative) - Normative references to international
         publications with their corresponding European
         publications

It provides basic time-critical messaging communications between devices in an automation environment. This protocol provides communication opportunities to all participating data-link entities in a synchronously-starting cyclic manner, according to a pre-established schedule, and in a cyclic or acyclic asynchronous manner, as requested each cycle by each of those data-link entities. Thus this protocol can be characterized as one which provides cyclic and acyclic access asynchronously but with a synchronous restart of each cycle. It includes the following significant changes with respect to the previous edition deletion of the former Type 6 fieldbus, and the placeholder for a Type 5 fieldbus data-link layer, for lack of market relevance; addition of new types of fieldbuses; division of this part into multiple parts numbered.