Rockwell Automation 5730 DriveLogix5730 Controller for PowerFlex 700S Drives with Phase II Control - Manual (Page 22)

1-10 What is DriveLogix5730?
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 the system overhead
percentage decreases execution time for the continuous task, it does
increase communications performance. However, increasing the system
overhead percentage also increases the amount of time it takes to execute a
continuous task - increasing overall scan time.
The following table shows the ratio between the continuous task and the
system overhead functions:
At the default time slice of 10%, system overhead interrupts the continuous
task every 9 ms (of continuous task time), as illustrated below.
At this time slice: The continuous tasks runs for: And then overhead occurs for up to:
10% 9 ms 1 ms
20% 4 ms 1 ms
33% 2 ms 1 ms
50% 1 ms 1 ms
TIP: For typical DriveLogix applications, a setting of 20-33% is
recommended.
Legend:
Task executes.
Task is interrupted (suspended).
periodic
1 ms 1 ms
system overhead
9 ms 9 ms
continuous task
0 5 10 15 20 25
elapsed time (ms)