Rockwell Automation 1756-HIST2G Historian ME 2.1 - Manual (Page 97)

5 • M ANAGING P OINTS
87
Input Points
An input point is a polled, advised, or high speed or triggered point when the data
flow is from a controller to the FactoryTalk Historian ME snapshot and archive. For
Trigger Input points, a separate trigger point must be configured. The input point is
associated with a trigger point by entering point attributes in the Extended
Description field for the input point as follows:
<keyword>=’<trigger_tag_name>’;<condition>
where the keyword is TRIG or EVENT, trigger_tag_name is the name of the trigger
point, and condition is Any, Anychange, Nonzero, Decrement, or Increment.
The FactoryTalk Historian ME automatically assumes a point is trigger-based, rather
than scan-based, when the <keyword>=’<trigger_tag_name>’;<condition> string is
found in the Extended Description field. An input is triggered when a new value is
sent to the snapshot of the trigger point.
Output Points
A point is an output (also known as a write back) point when the data is read from
from the FactoryTalk Historian ME archive to a controller. For Output points, the
timestamp of the trigger value must be greater than the timestamp of the previous
value. Output points are triggered in two ways:

By configuring a separate trigger point. The output point must have the same
point source as the interface, FTME. The trigger point can be associated with any
point source. The point type of the trigger point does not have to be same point
type as the Output point.
FactoryTalk Historian ME Archive
To External Data Source From External Data Source
Output points Trigger Input points
Controller
Controller
(Write back)