Rockwell Automation FactoryTalk View Site Edition Users Guide User Manual
Page 187
10
•
W
ORKING
WITH
TAGS
10–3
•
•
•
• •
10
•
Pla
ceho
lde
r
For example, if you specify a minimum of 0 and a maximum of 100, FactoryTalk View
would be able to read a value of 200 from a device and store it in memory, but would not
be able to write this value to the device.
Storing values in memory
Create HMI memory tags to store values without the need for an attached or accessible
device. For example, you can use memory tags to:
Store the result of a calculation.
Act as a temporary counter or index.
Maintain information about the system’s current state, for example, which graphic
display was last shown.
For more information about HMI memory tags, see “Data sources for HMI tags” on
page 10-17.
Reusing HMI tag names
HMI tags do not require hard-coded physical addresses or device-specific variable names.
This means you can reuse an application with other devices, by changing the physical
addresses that the HMI tag names are mapped to.
HMI tags can also have descriptive names, which you cannot create in some controllers or
OPC servers.
Monitoring alarms using HMI tags
HMI tags also provide an alternative method for triggering an alarm when a tag has a
certain value. You can set up alarm conditions for HMI analog and digital tags.
For more information, see Chapter 11, Setting up HMI tag alarms.
Using tag data in a FactoryTalk View SE application
A FactoryTalk View SE application can use a mix of data server tags and HMI tags,
depending on needs.
Following are the basic tasks involved in setting up the two types of tags.
To further define a range of values that can be written to a tag, you can specify a minimum and
maximum value for FactoryTalk View SE numeric input objects. For details, see “Validating
operator input” on page 17-24.
In FactoryTalk View SE, you can also use FactoryTalk Alarms and Events services to monitor
and control alarms. For information, see Chapter 12, Setting up FactoryTalk alarms.