工业通信网络 现场总线规范 第4-24部分:数据链路层协议规范 24型元件

[中文适用范围]： 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: in a asynchronously-starting cyclic manner, according to a pre-established schedule, or 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 asynchronous restart of each cycle. This part of IEC 61158 provides specifies 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 data link service provider; procedures for giving communications opportunities to all participating DL-entities (DLEs), sequentially and in a cyclic manner for deterministic and synchronized transfer at cyclic intervals up to 64 ms; procedures for giving communication opportunities available for time-critical data transmission together with non-time-critical data transmission without prejudice to the time-critical data transmission; procedures for giving cyclic and acyclic communication opportunities for time-critical data transmission with prioritized access; procedures for giving communication opportunities based on ISO/IEC/IEEE 8802-3 medium access control, with provisions for nodes to be added or removed during normal operation; the structure of the field bus DLP DUs used for the transfer of data and control information by the protocol of this document, and their representation as physical interface data units. 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 field bus 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. This document also specifies conformance requirements for systems implementing these procedures. This document does not contain tests to demonstrate compliance with such requirements. [外文原描述]： IEC 61158-4-24:2023 provides 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; procedures for giving communications opportunities to all participating DL-entities (DLEs), sequentially and in a cyclic manner for deterministic and synchronized transfer at cyclic intervals up to 64 ms; procedures for giving communication opportunities available for time-critical data transmission together with non-time-critical data transmission without prejudice to the time-critical data transmission; procedures for giving cyclic and acyclic communication opportunities for time-critical data transmission with prioritized access; procedures for giving communication opportunities based on ISO/IEC/IEEE 8802‑3 medium access control, with provisions for nodes to be added or removed during normal operation; the structure of the fieldbus DLPDUs used for the transfer of data and control information by the protocol of this document, and their representation as physical interface data units.