Rockwell Automation FactoryTalk Historian SE 4.0 Live Data Interface User Guide - Manual (Page 30)

Chapter 5 Point Configuration
30 Rockwell Automation Publication HSELD-UM024A-EN-E–September 2013
interface may not be able to tell with certainty that an output has
failed.
For Trigger Method 2, a separate trigger point is not configured. To
trigger an output, write a new value to the Snapshot of the output
point itself. The new value does not need to be different than the
previous value to trigger an output, but the time stamp of the new
value must be more recent than the previous value.
Trigger Method 2 may be easier to configure than Trigger Method
1, but Trigger Method 2 has a significant disadvantage. If the output
is unsuccessful, there is no tag to receive a digital state that is
indicative of the failure, which is very important for
troubleshooting.
See the following sample tag configurations:
• Scan Classes (page 30)
• Polled Tags (page 31)
• Advise Tags (page 31)
• Event Tags (page 31)
Scan classes are defined in the startup file. Each /F= parameter
defines a scan class, which is numbered in order.
For example, if the .bat file reads
/F=2 /F=1:00 /F=1:30:00 /F=00:00:05,00:00:01
then these scan classes have been defined:
• Scan Class 1 has a scan period of 2 seconds.
• Scan Class 2 has a scan period of 60 seconds.
• Scan Class 3 has a scan period of 5400 seconds (90 minutes).
Trigger Method 2
Sample Tag Configurations
Scan Classes