工业通信网络.现场总线规范.第6-23部分:应用层协议规范.第23类元件

[中文适用范围]： 工业自动化通信网络 - 现场总线规范 - 第 6-23 部分：应用层协议规范 - 23 型要素。该标准定义了工业环境中应用程序之间基本时间关键性和非时间关键性消息通信的通用要素，以及特定于 23 型现场总线的要素。时间关键性指在特定时间窗口内完成一个或多个指定动作的必要性，若未能完成，可能导致应用失败、设备损坏甚至危及人身安全。本标准以抽象方式定义了现场总线应用层不同类型的对外可见行为，包括：a) 定义通信应用程序实体之间传递的应用层协议数据单元的抽象语法；b) 定义传递的应用层协议数据单元的传输语法；c) 定义应用程序实体之间可见的服务行为的上下文状态机；d) 定义通信行为的应用关系状态机。本文件旨在定义用于确定 IEC 61158-5-23 中定义的服务原语的线表示，以及与这些服务传输相关的外部可见行为。本文件规定了符合 OSI 基本参考模型（ISO/IEC 7498）和 OSI 应用层结构（ISO/IEC 9545）的 IEC 现场总线应用层协议。 [外文原描述]： IEC 61158-6-23:2019 provides common elements for basic time-critical and non-time-critical messaging communications between application programs in an automation environment and material specific to Type 2 fieldbus. The term “time-critical” is used to represent the presence of a time-window, within which one or more specified actions are required to be completed with some defined level of certainty. Failure to complete specified actions within the time window risks failure of the applications requesting the actions, with attendant risk to equipment, plant and possibly human life. This International Standard specifies interactions between remote applications and defines the externally visible behavior provided by the Type 2 fieldbus application layer. The purpose of this document is to define the protocol provided to a) define the wire-representation of the service primitives defined in this document, and b) define the externally visible behavior associated with their transfer. This document specifies the protocol of the Type 2 fieldbus application layer, in conformance with the OSI Basic Reference Model (ISO/IEC 7498-1) and the OSI application layer structure (ISO/IEC 9545). This second edition includes the following significant technical changes with respect to the previous edition: - addition of the transmission extended mode and related attribute (Clauses 3.2.28, 4.1.9, 4.4, 5.2.9.2, and 5.3); - update of Table 4, Table 5, Table 16 and Table 48.