Trigger Routing and Reservation

What Are PXI Triggers?

PXI triggers are signals for synchronizing events between devices in a chassis. Devices in the chassis assert or deassert these signals, and they are passed to other devices through trigger lines on the chassis backplane. Each trigger bus on a chassis backplane contains eight PXI trigger lines (PXI_Trig0 through PXI_Trig7). Each slot in a PXI chassis is connected to a single trigger bus and can transmit and receive signals over the trigger lines from any other device on the same bus. Most chassis contain only a single trigger bus, but some chassis, such as the PXIe-1095, have multiple trigger buses.

Chassis with a Single Trigger Bus

In chassis containing only a single bus, all slots share the same trigger bus and can communicate to each other using this bus. For example, the PXIe-1082 chassis has one trigger bus, and all slots (1–8) reside on this trigger bus. In this situation, a device in any slot can use the backplane to send triggers to a device in any other slot.

Chassis with Multiple Trigger Buses

Without further configuration, chassis with multiple trigger buses function like three separate single-segment chassis. A device in a slot connected to one trigger bus cannot use the trigger lines to communicate to a device connected to another trigger bus. To see what slots are assigned to each trigger bus, refer to the Bus Mappings Legend area of the Trigger view for your chassis.

When properly configured, NI software automatically connects bus segments when an NI driver API references modules on different PXI buses.

Trigger route types are dynamic (the default), Away from Bus 1, Away from Bus 2, and Away from Bus 3.

Note  Refer to the NI KnowledgeBase article 32GFMIWD: Routing PXI Trigger Lines Across the Buses of Multisegment PXI Chassis, to learn more about trigger routing in PXI chassis with multiple trigger buses.