Rockwell Automation FactoryTalk View Machine Edition Users Guide - Manual (Page 87)

6 • Work with tags
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Use tag names that don’t exist
You can type the name of a tag that doesn’t yet exist. If you do this, ensure that you spell
every instance of the tag name consistently, and that when you do create the tag, you spell
it the same way you did when you referred to it.
When to use data server tags
For some of the things you want to do in your application, you might not need to create
HMI tags. Use direct references to tags located in devices instead, for example, tags
located in an OPC server’s database.
Eliminate duplication
Using data server tags allows you to add, modify, or delete tags in a device without having
to duplicate the changes in the FactoryTalk View HMI tag database.
Use complex data
Some devices, for example Logix5000 processors, support complex data types such as
arrays and structures. Your controller might have structures that contain hundreds of
member elements.
Referencing tag values directly eliminates the need for creating an HMI tag for each
member.
Steps for using data server tags
To use data server tags, complete three basic steps:
1. Create the tag in the OPC server or processor, or use an existing tag in the processor.
The server must understand the syntax of the device it is connected to. You need only
create a tag if you want to browse the server.
Examples of OPC servers include RSLinx Enterprise, RSLinx Classic, and
KEPServer Enterprise. For information about creating tags in OPC servers that have
their own tag database, see the documentation provided with the server.
For information about creating tags in a Logix5000 processor, see the documentation
for your device programming software.
2. Create a data server in FactoryTalk View, if your application doesn’t already have one.
Every new FactoryTalk View Machine application includes a RSLinx Enterprise data
server automatically.
Direct reference tags usually update faster than HMI tags. To obtain the best system
performance for your application, use direct reference tags where possible.