工业通信网络.现场总线规范.第6-28部分:应用层协议规范.28型元件

[中文适用范围]： 本标准规定了工业通信网络中现场总线的应用层协议规范，特别是类型28元素的相关内容。它涵盖了应用层协议数据单元（APDU）的结构、状态机的设计以及系统管理等方面的技术要求。 [外文原描述]： IEC 61158-6-28:2023 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 28 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 can cause failure of the applications requesting the actions, with attendant risk to equipment, plant and possibly human life.