61158-4-1-2014 Industrial communication networks – Fieldbus specifications – Part 4-1: Data-link layer protocol specification – Type 1 elements (Edition 2.0)
Réseaux de communication industriels – Spécifications des bus de terrain – Partie 4-1: Spécification du protocole de la couche liaison de données – ?léments de type 1 (Edition 2.0)
Industrial communication networks – Fieldbus specifications – Part 4-1: Data-link layer protocol specification – Type 1 elements (Edition 2.0) 是非强制性国家标准，您可以免费下载前三页
General The data-link layer provides basic time-critical messaging communications between devices in an automation environment. This protocol provides the data-link service by making use of the services available from the physical layer. The relationship between the International Standards for fieldbus data-link service@ fieldbus data-link protocol@ fieldbus physical service and systems management is described in IEC 61158-1. This protocol provides communication opportunities to all participating data- link entities a) in a cyclic asynchronous manner@ sequentially to each of those data-link entities@ and b) in a synchronous manner@ either cyclically or acyclically@ according to a pre-established schedule. The specified protocol also provides means of changing the set of participating data- link entities and of modifying the set of scheduled communications opportunities. W hen the set of scheduled communications opportunities is null@ the distribution of communication opportunities to the participating data-link entities is completely asynchronous. Thus this protocol can be characterized as one which provides access asynchronously but with a synchronous overlay. 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. NOTE In IEC 61158-4-1@ gray boxes have been used in the tables to indicate that the specified field is not a conceptual part of the specific DLPDU. Procedures The procedures are defined in terms of a) the interactions between peer DL-entities (DLEs) through the exchange of fieldbus DLPDUs; b) the interactions between a DL-service (DLS) provider and a DLS-user in the same system through the exchange of DLS primitives; c) the interactions between a DLS-provider and a Ph-service provider in the same system through the exchange of Ph-service primitives. Applicability These procedures are applicable to instances of communication between systems which support time-critical communications services within the data-link layer of the OSI or fieldbus reference models and which require the ability to interconnect in an open systems interconnection environment. Profiles provide a simple multi-attribute means of summarizing an implementation's capabilities@ and thus its applicability to various time-critical communications needs. Conformance This standard also specifies conformance requirements for systems implementing these procedures. This standard does not contain tests to demonstrate compliance with such requirements.