National Instruments NI-Motion - Manual (Page 209)

© National Instruments Corporation 14-1 NI-Motion User Manual
14
Onboard Programs
This chapter provides information about how onboard programs work for
the NI SoftMotion Controller and for NI 73xx motion controllers.
Using Onboard Programs with the NI SoftMotion
Controller
To use onboard programs with the NI SoftMotion Controller, use the
LabVIEW Real-Time Module (RT) to target your application to run in the
same environment as the NI SoftMotion Controller.
Because the NI SoftMotion Controller onboard program shares the same
processor and system resources with the NI SoftMotion Controller, ensure
you consider the following points before running your application in
LabVIEW RT:
• Ensure that your top level VI is configured to run at normal, above
normal, or high priority. If you are targeting LabVIEW RT for ETS,
use the timed loop instead of changing the priority of your top level VI.
• Follow the guidelines in the LabVIEW Real-Time Module User
Manual. The guidelines regarding memory allocation and using shared
resources are especially important.
• The jitter of the system increases with the number of devices used in
your RT system. Enable only the devices you need to use for the
current application.
• Because interrupts cause jitter, National Instruments recommends you
configure your application to poll for data periodically rather than wait
on an interrupt.
You can further decrease the jitter under ETS by configuring the
Ethernet mode to be polling. You configure these settings for the RT
controller in Measurement & Automation Explorer (MAX).
Under LabVIEW RT, the NI SoftMotion Controller runs in the
background at time critical priority. The NI SoftMotion Controller is
designed to consume less than 40% of the processor bandwidth. The
rate at which the NI SoftMotion Controller updates its data is typically
1 KHz for Ormec and 100 Hz for CANopen.