What is the Star Trigger on the PXI Backplane?

Updated Aug 15, 2018

Reported In


  • PXI Chassis

Issue Details

My PXI chassis has a PXI trigger bus that is linked to all slots. There is also a star trigger that is linked to slot 2 of the chassis. What is the difference between the star trigger and the triggers available through the PXI trigger bus?


The star trigger is a high-performance trigger line available to synchronize all of the modules in a PXI chassis. Although synchronization can be done using the normal PXI trigger bus, the star trigger is a trigger signal that offers increased synchronization performance. Specifically, the trigger signal has a propagation delay of no more than 5 ns and an inter-module delay of no more than 1 ns. The star trigger is designed such that the lengths of the wires from the star trigger slot to any other slots are identical.

The star trigger must be controlled from slot 2 of the PXI chassis. The trigger signal generated by the star trigger controller can be accessed by the other modules through the backplane. Alternatively, if the star trigger is not required, slot 2 can be used as a standard peripheral slot. 

This is the reason why slot 2 on the chassis is labeled with both a circle AND a diamond around the number 2. The diamond represents the ability for a module in this slot to be a star trigger controller; the circle indicates that the module in this slot can also be a standard module with no extra functionality.

For more information on the star trigger and the PXI backplane, please see the links below.