RSView Supervisory Edition Installation Guide

8 • WORKING WITH TAGS• • • • •Browsing for tagsIf you don’t know the names of tags, you can browse for them. You can browse whileonline and connected to a device, or you can browse for tags from an offline file, forexample, a PLC program file. To browse for tags, use the Tag Browser. For details, seepage 8-5.8 • PlaceholderUsing tag names that don’t existYou can type the name of a tag that doesn’t yet exist. If you do this, when you create thetag, and everywhere you use its name, make sure that you spell the tag name consistently.Using data server tagsFor some uses in an application, data server tags can offer advantages over HMI tags. Forexample, using direct references to tags in devices, or to tags located in an OPC server’sdatabase, can eliminate the need for duplication or provide access to complex data types.Eliminating duplicationUsing data server tags lets you add, modify, or delete tags in a device without having toduplicate the changes in the HMI tag database.Providing access to complex dataSome devices, for example, ControlLogix processors, support complex data types such asarrays and structures. A controller can have structures that contain hundreds of memberelements. Referencing tag values directly eliminates the need for creating an HMI tag foreach member.Setting up data server tagsThese are the tasks involved in setting up data server tags in an application:1. Create the tag in the OPC server, or processor, or use an existing tag in the processor.For information about creating tags in OPC-DA servers that have their own tagdatabase, see the documentation provided with the OPC-DA server.For information about creating tags in a ControlLogix processor, see the programmingsoftware documentation for ControlLogix.2. Create a data server in RSView, if the application doesn’t already have one.3. Anywhere you need to access a tag’s value, map an application component to the tag,through the data server. For example, map a tag to a graphic object, or add the tag to adata log model. At run time, the tag’s value is passed to the component it is mapped to.8-3