Full Description

This part of IEC 61158 describes basic packet communication services and models in an automation control industrial field environment. The Type 28 data-link layer provides time-critical and non-time-critical communication services. Time-critical refers to the requirement to complete specified functions between devices in a defined time window in an industrial field environment. Failure to complete specified functions within the time window can lead to failure or harm in industrial production.

This document defines in an abstract way the externally visible service provided by the Type 28 fieldbus data-link layer in terms of
a) function description;
b) primitive actions and events with primitive sequence diagram;
c) the form of externally service interface and related parameters.

The purpose of this document is to define the services provided to:
• the Type 28 fieldbus application layer at the boundary between the application and data-link layers of the fieldbus reference model;
• systems management at the boundary between the data-link layer and systems management of the fieldbus reference model.

Type 28 DL-service provides both a connected and a connectionless subset of those services provided by OSI data-link protocols as specified in ISO/IEC 8886.