Reserving Trigger Lines for PXI R Series Devices

National Instruments recommends that you reserve the trigger lines used by NI PXI R Series devices. If two PXI devices try to drive the same trigger line in different applications, or if the PXI devices are not programmed to work together, the application will not work and, in some cases, third-party PXI devices can be damaged. You can use Measurement & Automation Explorer (MAX) or the host VI to reserve trigger lines.

Reserving Trigger Lines in MAX

If you download and run the FPGA VI interactively, configure the PXI triggers in MAX. MAX maintains the trigger reservation for the R Series device even after you cycle power to the PXI chassis.

Reserving Trigger Lines in the LabVIEW FPGA Host VI

If you download and run the FPGA VI programmatically, reserve the trigger lines in the host VI. Use the Invoke Method function to reserve the trigger and to release the trigger reservation. LabVIEW releases the trigger reservation for the R Series device automatically when you close the FPGA VI reference. You must run the host VI again to reserve the trigger.

Reserving Trigger Lines

Complete the following steps to reserve a trigger line for a PXI R Series device.

1. Place the Open FPGA VI Reference function on the block diagram and configure it for the FPGA device and FPGA VI.
2. Place the Invoke Method function on the block diagram.
3. Wire the FPGA VI Reference Out output of the Open FPGA VI Reference function to the FPGA VI Reference In input of the Invoke Method function.
4. Wire the error out output of the FPGA VI Reference function to the error in input of the Invoke Method function.
5. Click the Invoke Method function and select Reserve PXI Trigger from the shortcut menu.
6. Right-click the Trigger input and select Create»Constant. An enum constant is created to help you select the trigger.

To reserve multiple trigger lines, repeat steps 2 to 6 for each trigger line you want to reserve, wiring the FPGA VI Reference Out output of the existing Invoke Method function to the FPGA VI Reference In input of the Invoke Method node that follows it.

Releasing Trigger Lines

Complete the following steps to release a trigger line for a PXI R Series device.

1. Place the Open FPGA VI Reference function on the block diagram and configure it for the FPGA device and FPGA VI.
2. Place the Invoke Method function on the block diagram.
3. Wire the FPGA VI Reference Out output of the Open FPGA VI Reference function to the FPGA VI Reference In input of the Invoke Method function.
4. Wire the error out output of the FPGA VI Reference function to the error in input of the Invoke Method function.
5. Click the Invoke Method function and select Unreserve PXI Trigger from the shortcut menu.
6. Right-click the Trigger input and select Create»Constant. An enum constant is created to help you select the trigger.

To release multiple trigger lines, repeat steps 2 to 6 for each trigger line you want to release, wiring the FPGA VI Reference Out output of the existing Invoke Method function to the FPGA VI Reference In input of the Invoke Method node that follows it.