IEC 61158的这一部分为自动化环境中设备之间的基本时间关键型消息通信提供了通用元素。术语“时间关键型”在本文中是指优先全双工无冲突时间确定性通信，其中一个或多个指定动作需要以某种确定的水平完成。如果未能在规定时间内完成规定的行动，则可能导致请求采取行动的应用程序失败，并对设备、装置以及可能的人身安全造成风险。交叉引用:ISO/IEC 7498- 3ISO/IEC/IEEE 8802-3ISO/IEC 7498-1ISO/IEC 10731ISO/IEC TR 8802-1IETF RFC 791IEC 61588IETF RFC 768IEC 61158-6-21:2019IEC 61158-5-21:2019IEC 611784-2:2019IEC 61158-1:2019替换BS EN 61158-3-21:2012，其保持最新状态购买本文件时可提供的所有当前修改件均包含在购买时。

This part of IEC 61158 provides the common elements for basic time-critical messaging communications between devices in an automation environment. The term "time-critical" in this context means the prioritized full-duplex collision-free time-deterministic communication, of which one or more specified actions are required to be completed with some defined level of certainty. Failure to complete specified actions within the required time risks the failure of the applications requesting the actions, with attendant risk to equipment, plant, and possibly human life.Cross References:ISO/IEC 7498-3ISO/IEC/IEEE 8802-3ISO/IEC 7498-1ISO/IEC 10731ISO/IEC TR 8802-1IETF RFC 791IEC 61588IETF RFC 768IEC 61158-6-21:2019IEC 61918:2018IEC 61158-5-21:2019IEC 61784-2:2019IEC 61158-1:2019Replaces BS EN 61158-3-21:2012 which remains currentAll current amendments available at time of purchase are included with the purchase of this document.