There are multiple reasons why this is
not a supported feature for triggering under Windows and why NI does not recommend using the controller's SMB connector for this purpose. National Instruments has hardware that was designed specifically for extremely accurate clock generation, synchronization, and triggering between PXI chassis (
PXI-665x) and other recommended alternatives listed below.
Non-deterministic propagation delays1. The controller's SMB input is not guaranteed to have a defined propagation delay to the backplane. This means the SMB trigger on the Windows PXI controller is useless for customers that want deterministic triggering. Unlike our
PXI-665x boards which have a maintained API and precise triggering properties, the PXI controller's SMB connector and routing circuitry is intended for Watchdog use under LabVIEW RT and isn't designed for this use case. A trigger propagating through the SMB circuitry and going to the backplane, or vice-versa, could have a great deal of variance in the propagation delay which
makes gathering useful triggers impossible. This propagation delay is not something National Instruments specs.
An excellent available workaround: Use the measurement hardware's trigger inputs2. The triggering inputs on our measurement hardware (that customers likely have in their system) can route triggering signals to the PXI backplane (usually through PFI lines) with deterministic results. This functionality is fully supported in most of our APIs and will be maintained between generations of devices.
NOT backward or forward compatible3. The SMB input is
NOT guaranteed to be compatible between different versions of our PXI controllers under Windows. The hardware properties along with an excellent workaround are the reason we do not support doing routing of triggers through the SMB connector on our PXI family of embedded controllers under Windows. If you are still interested in the beta software despite the shortcomings, visit
www.ni.com/support and submit an e-mail request.
Adam Ullrich
PXI/VXI Product Support Engineer
National Instruments