Comitato Elettrotecnico Italiano

Industrial communication networks - Fieldbus specifications Part 4-22: Data-link layer protocol specification - Type 22 elements
 N EN 61158-4-22

Annotation

General

The data-link layer provides basic time-critical messaging communications between devices in an automation environment.

This protocol provides communication opportunities to all participating data-link entities

a) in a synchronously-starting cyclic manner, according to a pre-established schedule, and

b) 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.

Specifications

This standard specifies:

a) procedures for the timely transfer of data and control information from one data-link user entity to a peer user entity, and among the data-link entities forming the distributed datalink service provider;

b) the structure of the fieldbus DLPDUs used for the transfer of data and control information by the protocol of this standard, and their representation as physical interface data units.

Procedures

The procedures are defined in terms of:

a) the interactions between peer DL-entities (DLEs) through the exchange of fieldbus DLPDUs;