標準號：IEC 61158-3-18-2007
中文標準名稱：工業通訊網絡.數據總線規范.第3-18部分:數據聯絡層設備定義.18型元件
英文標準名稱：Industrial communication networks - Fieldbus specifications - Part 3-18: Data-link layer service definition - Type 18 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 standard provides common elements for basic time-critical and non-time-criticalmessaging communications between devices in an automation environment and materialspecific to Type 18 fieldbus. The term “time-critical” is used to represent the presence of atime-window, within which one or more specified actions are required to be completed withsome defined level of certainty. Failure to complete specified actions within the time windowrisks failure of the applications requesting the actions, with attendant risk to equipment, plantand possibly human life.This standard defines in an abstract way the externally visible service provided by the Type18 fieldbus 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.This standard defines the services provided to? the Type 18 fieldbus application layer at the boundary between the application and datalinklayers of the fieldbus reference model, and? system 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, including:a) 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 do they constrainthe implementations 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 18 data-link layer services defined in this standard.