Rockwell Automation Logix5000 Controllers Tasks, Programs, and Routines Programming Manual - Manual (Page 38)

Chapter 2 Manage event tasks
Term Definition
•
The RPI specifies when the module multicasts the current contents of the input data
buffer without scanning (updating) the channels.
• The module resets the RPI timer each time an RTS transfer occurs.
Change of state (COS) The COS parameter instructs a digital input module to multicast data whenever a specified
input point transitions from On → Off or Off → On.
•
You enable COS on a per-point basis.
• When any point that is enabled for COS receives the specified change, the module
multicasts the data for all its points.
• By default, COS is enabled for both On → Off and Off → On changes for all points.
• You must specify an RPI regardless of whether you enable COS. If a change does not occur
within the RPI, the module sends its data at the RPI.
The following table summarizes when an input module multicasts its data and
triggers an event task within its own chassis.
If the input module is And Then it multicasts data And it triggers an event task
Digital COS is enabled for any point on
the module
• When any point that is enabled for COS receives the specified
change
• At the RPI
When any point that is enabled for COS receives
the specified change
COS is not enabled for any
point on the module At the RPI Never
Analog RTS ≤ RPI At the RTS (newly updated channel data) At the RTS for the module
RTS > RPI
• At the RTS (newly updated channel data)
• At the RPI (does not contain updated data from the channels)
At the RTS for the module
If the module is in a remote chassis, only the RPI determines when the controller
receives the data and event trigger over the network.
Over this network Controller receives the data
EtherNet/IP Close to the RPI, on average
ControlNet At the actual packet interval (≤ RPI)
The following examples show COS and RTS configurations.
Important: If you use a digital module to trigger an event task, configure only one point on the module for COS. If you
configure multiple points, a task overlap could occur.
38 Rockwell Automation Publication 1756-PM005-EN-P - October 2014