Rockwell Automation 1756-XXXX ControlLogix Analog I/O Modules - Manual (Page 26)

26 Publication 1756-UM009C-EN-P - December 2010
Chapter 2 Analog I/O Operation in the ControlLogix System
If the RTS value is greater than the RPI, the module produces at both the RTS
rate and the RPI rate. Their respective values will dictate how often the
owner-controller will receive data and how many multicasts from the module
contain updated channel data.
In the example below, the RTS value is 100 ms and the RPI value is 25 ms.
Only every fourth multicast from the module will contain updated channel
data.
Triggering Event Tasks
When configured, ControlLogix analog input modules can trigger an event
task. The event task lets you execute a section of logic immediately when an
event (that is, receipt of new data) occurs.
Your ControlLogix analog I/O module can trigger event tasks every RTS, 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.
RTS
100 ms - Updated data
RPI
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 RTS but not at the RPI. For example, in the illustration
above, an event task can be only triggered every 100 ms.