1.1<\/b> Overview<\/p>\n
This standard provides common elements for basic time-critical messaging communications between devices in an automation environment. The term \u201ctime-critical\u201d 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.<\/p>\n
This standard defines in an abstract way the externally visible service provided by the Type 19 fieldbus data-link layer in terms of<\/p>\n
the primitive actions and events of the service;<\/p>\n<\/li>\n
the parameters associated with each primitive action and event, and the form which they take; and<\/p>\n<\/li>\n
the interrelationship between these actions and events, and their valid sequences. The purpose of this standard is to define the services provided to<\/p>\n<\/li>\n<\/ol>\n
the Type 19 fieldbus application layer at the boundary between the application and data- link layers of the fieldbus reference model, and<\/p>\n<\/li>\n
systems management at the boundary between the data-link layer and systems management of the fieldbus reference model.<\/p>\n<\/li>\n<\/ul>\n
1.2<\/b> Specifications<\/p>\n
The principal objective of this standard is to specify the characteristics of conceptual data-link layer services suitable for time-critical communications, and thus supplement the OSI Basic Reference Model in guiding the development of data-link protocols for time-critical communications. A secondary objective is to provide migration paths from previously-existing industrial communications protocols.<\/p>\n
This standard 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 to address implementation issues not covered by this specification, including:<\/p>\n
the sizes and octet ordering of various multi-octet service parameters, and<\/p>\n<\/li>\n
the correlation of paired request and confirm, or indication and response, primitives.<\/p>\n<\/li>\n<\/ol>\n
1.3<\/b> Conformance<\/p>\n
This standard does not specify individual implementations or products, nor do they constrain the implementations of data-link entities within industrial automation systems.<\/p>\n
There is no conformance of equipment to this data-link layer service definition standard. Instead, conformance is achieved through implementation of the corresponding data-link protocol that fulfills the Type 19 data-link layer services defined in this standard.<\/p>\n
| PDF Pages<\/th>\n | PDF Title<\/th>\n<\/tr>\n | ||||||
|---|---|---|---|---|---|---|---|
| 6<\/td>\n | CONTENTS <\/td>\n<\/tr>\n | ||||||
| 7<\/td>\n | INTRODUCTION <\/td>\n<\/tr>\n | ||||||
| 8<\/td>\n | 1 Scope 1.1 Overview 1.2 Specifications 1.3 Conformance <\/td>\n<\/tr>\n | ||||||
| 9<\/td>\n | 2 Normative references 3 Terms, definitions, symbols, abbreviations and conventions 3.1 Reference model terms and definitions <\/td>\n<\/tr>\n | ||||||
| 10<\/td>\n | 3.2 Service convention terms and definitions <\/td>\n<\/tr>\n | ||||||
| 11<\/td>\n | 3.3 Data-link service terms and definitions <\/td>\n<\/tr>\n | ||||||
| 13<\/td>\n | Figure 1 \u2013 Relationships of DLSAPs, DLSAP-addresses and group DL addresses <\/td>\n<\/tr>\n | ||||||
| 14<\/td>\n | 3.4 Symbols and abbreviations <\/td>\n<\/tr>\n | ||||||
| 15<\/td>\n | 3.5 Common conventions <\/td>\n<\/tr>\n | ||||||
| 16<\/td>\n | 4 Data-link services and concepts 4.1 Overview <\/td>\n<\/tr>\n | ||||||
| 17<\/td>\n | Tables Table 1 \u2013 Summary of DL services and primitives <\/td>\n<\/tr>\n | ||||||
| 18<\/td>\n | 4.2 Service channel services (SVC services) <\/td>\n<\/tr>\n | ||||||
| 19<\/td>\n | Table 2 \u2013 Read (RD) <\/td>\n<\/tr>\n | ||||||
| 20<\/td>\n | 4.3 Hot-plug services Table 3 \u2013 Write (WR) Table 4 \u2013 Enable_Hotplug (EHP) <\/td>\n<\/tr>\n | ||||||
| 21<\/td>\n | 4.4 Realtime channel setup services (RTCS services) Table 5 \u2013 Notify_Hotplug (NHP) <\/td>\n<\/tr>\n | ||||||
| 22<\/td>\n | Table 6 \u2013 Initiate_cyclic_communication (ICC) <\/td>\n<\/tr>\n | ||||||
| 23<\/td>\n | 4.5 RTC services Table 7 \u2013 Disable_cyclic_communication (DCC) Table 8 \u2013 Notify_Error (NER) <\/td>\n<\/tr>\n | ||||||
| 24<\/td>\n | Table 9 \u2013 Write_cyclic (WRC) Table\u00a010 \u2013 Get_Device_Status (GDS) <\/td>\n<\/tr>\n | ||||||
| 25<\/td>\n | Table 11 \u2013 Write_Device_Status (WDS) <\/td>\n<\/tr>\n | ||||||
| 26<\/td>\n | Table 12 \u2013 Notify_Network_Status_Change (NNSC) <\/td>\n<\/tr>\n | ||||||
| 27<\/td>\n | Bibliography <\/td>\n<\/tr>\n<\/table>\n","protected":false},"excerpt":{"rendered":" Industrial communication networks. Fieldbus specifications – Data-link layer service definition. Type 19 elements<\/b><\/p>\n |