Rockwell Automation FactoryTalk Historian SE 3.0 UniInt Interface User Guide - Manual (Page 28)

Historian Point Configuration
22
New API
functions Interface
Requires
SDK /PISDK
Startup
Parameter Max Tag
Name Max
Instrument
Tag Max
Extended
Descriptor
no no 0 254 32 83
no no 1 1023 1023 1023
no yes na 1023 1023 1023
yes na na 1023 1023 1023
Input Points
Input points are used to write data to the Historian Data Archive. Each interface has its own
rules for determining whether a given point is an input point or an output point. There is no
de facto Historian point attribute that distinguishes a point as an input point or an output
point.
Input points can be scan-based, trigger-based, or unsolicited.
Scan-based Inputs
For scan-based input points values are sent to the points on a periodic basis. Scanning
periods are defined by the /f parameter on the startup-command-line of the interface. The
first appearance of the /f parameter on the command-line is referred to as the first scan
class, the second appearance of the /f parameter is referred to as the second scan class, and
so on.
The Location4 Historian point attribute is used to associate an input point with a given scan
class. For example, to associate a particular input point with scan class 1, set Location4 to 1
for the point.
Trigger-based Inputs
For trigger-based input points, a separate trigger point must be configured. An input point is
associated with a trigger point by entering a case-insensitive string in the extended descriptor
(ExDesc) Historian point attribute of the input point of the form:
keyword=trigger_tag_name
where keyword is replaced by ―event‖, ―trig‖ or ―trigger‖ and trigger_tag_name is
replaced by the name of the trigger point. UniInt automatically assumes that an input point is
trigger-based instead of scan-based when the keyword=trigger_tag_name string is
found in the extended descriptor attribute.
An input is triggered when a new value is sent to the Snapshot of the trigger point. The new
value does not need to be different than the previous Snapshot value to trigger an input, but
the timestamp of the new value must be greater than (more recent than) or equal to the