Defining Tag Parameters; Accessing Tag Parameters During Development - Eaton XV-102 Series Quick Start Manual

XV Operator Interface Models
with Visual Designer
When finished,
place mouse
cursor over
this tab, right
click and select
Close, or just
click on the "x"
in the tab.
Once you have defined the Class Members for cTank, close the
Class definition Worksheet by clicking on the "x" in the tab of the
Class definition Worksheet.
We have just completed the first part of defining a Class tag, i.e.
defining the Class. The next step is to declare the Class tag in the
Project Tags database. Open the Project Tags folder and select
Datasheet View.
As shown in the graphic below, we have now defined a Class
tag called tank and its data type is cTank, the newly defined
Class definition.
Declaring a Class Tag
Now that we have defined the Class cTank and declared Class Tag
tank, let's look at the syntax for using a Class Tag. The syntax is:
ClassTag.Member (e.g. tank.Level, tank.Pressure, etc.).
Suppose we had three (3) tanks instead of a single Tank. We could
declare three Class tags of type cTank (e.g. Tank1, Tank2, Tank3). But
a better way might be to declare an Array of Class tags. Using the
above example, we simply add a size of 3 to the Size field as show
below.
Declaring an Array of Class Tags
Note that since Size is set to 3, there are actually four (4) elements
to Array of Class tags. To access a specific tank in the Array of Class
tags, we would use the following syntax: ClassTag[index].Member
(e.g. tank[1].level, tank[2].pressure, etc.).

3.4.8 Defining Tag Parameters

As previously discussed, Visual Designer tags are not simply
variables. Every Visual Designer tag has a number of Properties
associated with it. Certain tag Properties are only accessible in the
development environment. Some tag Properties are available in the
development environment and during runtime, while others are only
accessible during runtime. Tags that are accessible during runtime
are called Tag Fields. Some runtime Tag Fields are Read-Only while
others are Read-Write.
Quick Start Guide MN0480001E
Some of the Tag Parameters are very useful, depending on your
application. Some Tag Properties (Fields) worth noting are:
Max & Min values: These are minimum and maximum values for
a tag. If exceeded, a warning occurs. These values can be changed
during runtime
Quality: Indicates whether an improper evaluation occurred (e.g.
divide by 0), or if there was a bad read from a communication driver
(e.g. read or write error to a PLC, read or write error from the OPC
Server to a PLC or other device)
TimeStamp: Tells you when a tag last changed value
Alarm Status &: Allows you to set Alarm Limits at runtime, check to
see if an alarm is
Alarm Limits: active (caused by the tag), and to clear any alarm
caused by the tag

3.4.9 Accessing tag parameters during development

Scope. However, if you position your mouse cursor in any row of the
Datasheet View and click the right mouse button, you will get a list
of options. At the bottom on this list of options is the option to view
additional (Property) columns.
In the Datasheet view, these additional columns are:
Startup: An initial startup value for the tag if the Retentive Value
option is unchecked.
Min: A minimum value that is allowed for the Tag. If the tag evalu-
ates to a value below the minimum, a warning to the LogWin
Window will occur. Values below the Minimum are not allowed to be
entered by any Object (e.g. Text I/O).
Max: A minimum value that is allowed for the Tag. If the tag evalu-
ates to a value below the minimum, a warning to the LogWin
Window will occur. Values below the Minimum are not allowed to be
entered by any Object (e.g. Text I/O).
Unit: A text field used to describe the engineering units for the tag.
Retentative Value: A checkbox that, if checked, tells the Visual
Designer database manager to save all changes to a Tag's value dur-
ing runtime operation.
N ote: checking this option can cause frequent access to your XV's flash
device, based on your application
Retentative Parameters: A checkbox that, if checked, tells the Visual
Designer database manager to save all changes to the Tag's Field
values during runtime.
eaton Corporation www.eaton.com
Effective February 2011
Actually, we have already
seen some of the tag
Properties in the Project
Tags Database (e.g. Size
and Description). Visual
Designer provides two
(2) methods of accessing
Tag Properties in the
development environ-
ment. The first is in the
Project Tags Database,
and the second is by
selecting a Project tag in
the Project Tags database
and selecting the Tag
Properties icon in the
Toolbar.
Open the Project Tags
folder in the Database
Tab of the Workspace.
Select Datasheet View.
Note that the default tag
Properties that are dis-
played are Name, Size,
Type, Description, and
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