15 Symbol File Configurator Too
15.2The Meaning of Symbols
Definitions
The terms listed below are important in conjunction with the Symbol File
Configurator:
Term |
| Meaning |
|
| |
OPC ItemID | The OPC ItemID is the identifier of a process variable used | |
| by the OPC server. | |
| An ItemID is transferred by the OPC client to the OPC | |
| Server to identify a process variable and is unique for the | |
| OPC Server. | |
| It is either a symbolic name or a runtime name. | |
|
| |
Symbolic name | A symbolic name is an OPC ItemID that was generated by | |
| the Symbol File Configurator. In a hierarchically structured | |
| name space, a symbolic name is made up of the names of | |
| the hierarchical levels and the actual symbol. | |
| Example: | |
| Plant_Packing.Conveyor.Limit_Switch | |
|
| |
Runtime name | A runtime name is an OPC ItemID that contains protocol | |
| and address information to allow the assignment and that is | |
| accepted directly by the OPC Server without the use of a | |
| symbol file. Using the Symbol File Configurator, a symbolic | |
| name is assigned to a runtime name. | |
| Examples: | |
| S | DP:[CP.5613]Slave1M003_IB0 |
| S | FMS:[Connection1]14 |
| S | S7:[S7_1.Connection]MW5 |
|
|
|
Accessing Process Variables using Symbols
An OPC client normally accesses process variables using ItemIDs that contain address information. It is, however, also possible to access the variables using symbolic names that can be structured hierarchically.
These names that are independent of the protocol and device are known as symbols. In contrast, the variable names that include information about the communications path and type in their syntax are known as runtime names.
Example of a symbol: Conveyor_1.drive_1.lim_switch
Example of a runtime name: S7:[Connection_1]EX3.1
Commissioning PC Stations - Manual and Quick Start | 195 |
Release 5/2005 |
