Rockwell Automation 5720 DriveLogix System - Manual (Page 56)

Publication 20D-UM002C-EN-P - November 2003
2-22 What Is DriveLogix?
Selecting a System
Overhead Percentage The Controller Properties 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, including block-transfers
• 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.
If communications are not completing fast enough, increase the system
overhead percentage. As you increase the system overhead percentage, the
overall program scan also increases.
1. View properties for the controller and select the Advanced tab.