Rockwell Automation 1756-OF8H ControlLogix HART Analog I/O Modules - Manual (Page 43)

Rockwell Automation Publication 1756-UM533C-EN-P - February 2011 43
ControlLogix Module Operation Chapter 3
In the example below, the real time sample value is 100 ms and the requested
packet interval value is 25 ms. Only every fourth multicast from the module
contains updated channel data.
Trigger Event Tasks
When configured to do so, ControlLogix analog input modules can trigger an
event task. The event task offers ControlLogix controller users a task that
executes a section of logic immediately when an event (receipt of new data)
occurs.
Your ControlLogix analog I/O module can trigger event tasks every real time
sample, after the module has sampled and multicast its data. Events tasks are
useful for synchronizing process variable (PV) samples and proportional integral
derivative (PID) calculations.
Real Time Sample (RTS)
100 ms - Updated data
Requested Packet
Interval
25 ms - Same input data
as the previous RTS
25 50 75 100 125 150 175 200 225 250 275 300 325 350 375 400
Time (ms) 40946
IMPORTANT ControlLogix analog I/O modules can trigger event tasks at
every real time sample, but not at the requested packet
interval. For example, in the figure, an event task can be only
triggered every 100 ms.