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Windows Considerations
Appendix D
System Overhead Timeslice
All Logix-based controllers have a configuration setting for the system overhead
timeslice. This function lets the controller take care of communication requests
that occur from other controllers or from queued requests from within the
controller’s application program. The timeslice switches the priority level of the
continuous task with that of the background communication task, which is
always running at a lower level than the continuous task.
The timeslice setting is a percent value that is applied to a 100 ms background
timing window. With a setting of 10% (the default), for every 100 ms of real time,
there is 10 ms of time when the communication task priority is higher than the
continuous task. If there is communication activity to perform, the controller
does it and when completed, the controller lets the continuous task run again
during that 10 ms window. For the next 90 ms, the continuous task is at its
normal priority and the communication task is lower. During dwell time, if there
are communication tasks ready to run, they will run during the dwell even though
the communication task is not switched to a higher priority. And any periodic
task that needs to run overrides both the continuous task and the
communication task.
Multiple SoftLogix Controllers in the Virtual Chassis
Multiple controllers in the virtual chassis, executing on a computer with only one
CPU, is less efficient than one controller. With multiple controllers, the
Windows operating system has to take time to swap threads in a round-robin
fashion, assuming all the controllers have a continuous task and a very small
dwell. If your computer has multiple CPUs, then assign multiple controllers
across the multiple CPUs.
HMI Considerations
Considerations when running an HMI and a SoftLogix controller on the same
computer include the following.
Consideration
Description
HMI initialization
Make sure RSLinx software and the SoftLogix controller completely initialize on the computer before the HMI begins to
initialize. Otherwise, you may experience memory assignment anomalies.
Network connection
If the computer loses the network connection (there is no connection to a local switch), on Powerup, Windows 2000/XP
do not initialize Ethernet ports or the TCP/IP stack. This results in the HMI not being able to communicate with the
SoftLogix controller because the HMI uses the TCP/IP stack. To avoid this, use a loopback adapter for communication.
