Rockwell Automation 1794-L34 FlexLogix Controller System User Manual - Manual (Page 82)

Publication 1794-UM001G-EN-P - January 2007
82 Develop Applications
4. Develop a routine for the Controller Fault Handler. See the
Logix5000 Controllers Common Procedures, publication
1756-PM001.
Select a System
Overhead Percentage The Controller Properties dialog lets you specify a percentage for
system overhead. This percentage specifies the percentage of
controller time (excluding the time for periodic tasks) that is devoted
to communication and background functions.
System overhead functions include:
• communicating with programming and HMI devices (such as
RSLogix 5000 software)
• responding to messages
• sending messages
• re-establishing and monitoring I/O connections (such as RIUP
conditions); this does not include normal I/O communications
that occur during program execution
• bridging communications from the serial port of the controller to
other communication devices
The controller performs system overhead functions for up to 1 ms at a
time. If the controller completes the overhead functions in less than
1 ms, it resumes the continuous task.
As the system overhead percentage increases, time allocated to
executing the continuous task decreases. If there are no
communications for the controller to manage, the controller uses the
communications time to execute the continuous task. While increasing
1. View properties for the controller and select the Advanced tab.