標準號：IEC 61158-3-7-2007
中文標準名稱：工業通訊網絡.現場總線規范.第3-7部分:數據聯絡層設備定義.7型元件
英文標準名稱：Industrial communication networks - Fieldbus specifications - Part 3-7: Data-link layer service definition - Type 7 elements
標準類型：N18;P76
發布日期：1999/12/31 12:00:00
實施日期：1999/12/31 12:00:00
中國標準分類號：N18;P76
國際標準分類號：25.040.40;35.100.20;35.160
適用范圍：1.1 OverviewThis part of IEC 61158 provides common elements for basic time-critical messagingcommunications between devices in an automation environment. The term “time-critical” isused to represent the presence of a time-window, within which one or more specified actionsare required to be completed with some defined level of certainty. Failure to complete specifiedactions within the time window risks failure of the applications requesting the actions, withattendant risk to equipment, plant and possibly human life.This standard defines in an abstract way the externally visible service provided by the Type 7fieldbus data-link layer in terms ofa) the primitive actions and events of the service;b) the parameters associated with each primitive action and event, and the form which theytake; andc) the interrelationship between these actions and events, and their valid sequences.The purpose of this standard is to define the services provided to? the Type 7 fieldbus application layer at the boundary between the application and data-linklayers of the fieldbus reference model, and? systems management at the boundary between the data-link layer and systemsmanagement of the fieldbus reference model.1.2 SpecificationsThe principal objective of this standard is to specify the characteristics of conceptual data-linklayer services suitable for time-critical communications, and thus supplement the OSI BasicReference Model in guiding the development of data-link protocols for time-criticalcommunications. A secondary objective is to provide migration paths from previously-existingindustrial communications protocols.This specification may be used as the basis for formal DL-Programming-Interfaces.Nevertheless, it is not a formal programming interface, and any such interface will need toaddress implementation issues not covered by this specification, includinga) the sizes and octet ordering of various multi-octet service parameters, andb) the correlation of paired request and confirm, or indication and response, primitives.1.3 ConformanceThis standard does not specify individual implementations or products, nor does it constrain theimplementations of data-link entities within industrial automation systems.There is no conformance of equipment to this data-link layer service definition standard.Instead, conformance is achieved through implementation of the corresponding data-linkprotocol that fulfills the Type 7 data-link layer services defined in this standard.