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, or
b) in an acyclic manner, as requested 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.dition 1.0 2014-08 INTERNATIONAL STANDARD NORME INTERNATIONALE Industrial communication networks – Fieldbus specifications – Part 4-24: Data-link layer protocol specification – Type 24 elements Réseaux de communication industriels – Spécifications des bus de terrain – Partie 4-24: Spécification du protocole de la couche liaison de données – éléments de type 24 IEC 61158-4-24:2014-08(en-fr) THIS PUBLICATION IS COPYRIGHT PROTECTED