IEC 62769-3:2021 pdf free download – Field device integration (FDI)
FDI Packages provide Business Logic that is used by the FDI Server to maintain the integrityof the Information Model.The Business Logic specified in an FDl Package can invoke builtinfunctions that shall be implemented by the FDI Server. The builtin functions that shall beimplemented by the FDI Server are specified in IEC 61804-5.
5.2OnlinelOffline
5.2.1 overview
The Information Model maintained by the FDl Server contains online and offline values.Theonline values reflect values in a physical componentldevice.The offline values reflect valuesstored in a configuration database.
The offline values are updated through write service requests from an FDl Client or BusinessLogic executed by the FDI Server. The offline values are not updated when the FDI Serverreads data from the device or writes data to the device.
The online values in the lnformation Model are not updated through write service requests.Successful write service requests through the Information Model result in value changes inthe physical devices. The online values in the Information Model will then be updated as aresult of read service requests or subscriptions.
FDI Servers can provide a server-specific mechanism for creating Device Instances withoutthe presence of physical hardware.The FDl Server creates these instances using informationin FDl Packages. All read/write requests for online values for Device Instances with nophysical device shall return an error.
The transfer of information between the offline values and the physical device is supportedthrough the TransferToDevice and TransferFromDevice methods in the Information’ Model.These Methods shall implement the download and upload procedures，respectively，asspecified in lEC 61804-4.When no implementation is provided based on lEC 61804-4，thenthese Methods shall return Bad_NotSupported, as per lEC 62541-4.
The Device shall have been locked prior to invoking these methods, as specified inIEC 62769-5.
5.2.2 Transfer to device
The TransferToDevice method shall implement the download procedure as specified inIEC 61804-4.This transfers the offline values to the physical device.
As a general rule, the FDI Server should not change the Online variable node when writing avalue to the device.The Online variable node should be updated only in the process of readoperations or subscriptions. Notwithstanding, as specified in lEC 62769-5, the FDI Server willreset any cached Value for the target Nodes in the Information Model so that they will be re-read next time they are requested.
Figure 3 shows two possible Server strategies and how the Client can adapt. In the lowerscenario,the Server provides a single EditContext instance for all dialogs.Here, the Clientgroups all dialogs and exposes a single set of buttons to Apply and Cancel, because it alwaysconcerns all edits.
In the upper scenario，the Server provides multiple EditContext instances,one of them aschild of another one.Each instance can be addressed separately. lf the changes in a childinstance are applied, they are transferred to the parent. If the changes in a root instance areapplied, they are transferred to the Device.
The Client can call GetEditContext multiple times，for instance when it opens an additionaledit window or for a completely separate dialog (diagnosis in parallel to configuration). lt is upto the Server strategy whether it returns a new instance or the same instance.The Client isexpected to adapt its user interface to the EditContext strategy of the Server. See Figure 3 forhow Clients may position the Apply and Cancel buttons so that the User clearly understandswhich changes are applied or discarded.