Rockwell Automation FactoryTalk View Machine Edition Users Guide - Manual (Page 103)

7 • Use HMI tags
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Memory
A tag with memory as its data source receives its data from (and stores values in) the
FactoryTalk View internal value table. Tags with memory as the data source do not count
toward the total tag limit.
For analog tags with Memory as the data source, select the data type that matches the
format of the data you will store in the tag. Choosing Default is the same as choosing
Floating Point.
Address syntax for device tags
For device tags, you must provide the address and path to the OPC server that is
connected to the data source. For example, the OPC server could be connected to a device
such as a programmable controller.
The syntax for OPC tag addresses is:
[AccessPath]Address
or
::[AccessPath]Address
where :: indicates that the address resides in a data server in the application. (The two
colons are necessary when the address contains a colon, for example, N7:0.)
The access path is one of the following:
 For communications with an RSLinx Enterprise data server, the access path is the
name of the device shortcut in RSLinx Enterprise.
 For communications with an RSLinx Classic OPC server, the access path is the name
of an OPC topic in RSLinx Classic.
 For communications with other OPC servers, the access path might be optional. For
information about the syntax for the access path, see your OPC server documentation.
Example: Logix5000 addressing
We recommend that you use the Tag Browser or Find and Replace to select OPC items.
When you use the Tag Browser the correct syntax and data types are selected
automatically.
However, if you want to define tags before setting up communications, you can type the
address manually, as shown in this example. If you type the address manually, be sure to
select the data type for the tag that matches the data type used by the Logix5000
processor. If you use the Default data type, values are treated as floating-point values.
The square brackets are part of the syntax. They do not indicate optional parameters.