Timing, Triggering, and Synchronization Capabilities of the NI PXI-1422

Overview
The National Instruments PXI-1422 16-bit digital image acquisition (IMAQ) device supports a set of signal-sharing lines called Real-Time System Integration (RTSI). Individual PCI-1422 devices can be cabled together using the RTSI bus for signal sharing, triggering, and synchronization. RTSI lines on PXI-1422 devices are directly mapped to the PXI trigger bus and allow sharing of signals over the PXI backplane without additional cabling. Table 1 shows how these RTSI lines directly map to the PXI backplane for integration with any industry-standard PXI capable of communicating with the indicated PXI backplane lines. Table 2 lists the signals that can be mapped to the PXI backplane.


Note: You can use all four external triggers and up to four RTSI lines simultaneously.

Star Trigger Capability
The PXI-1422 does not support driving or receiving the Star Trigger. If placed in slot 2 of the PXI chassis (the Star Trigger slot), the PXI-1422 will function as if it is in a generic PXI slot. The PXI-1422 can, however, drive and receive signals on the RTSI_6 (PXI Trigger 6) line, which is commonly confused with the Star Trigger line

IMAQ Trigger Functions
The following functions use trigger lines or RTSI lines with IMAQ products:

IMAQ Trigger Drive—This function allows you to route internal signals to RTSI or External Trigger lines. You can only route out at most four internal signals at once. The HSYNC, VSYNC, Frame Start, and Frame Done require more resources, and you can route two of these signals to RTSI or an External Trigger line at once. Acquisition in Progress, Acquisition Done, Unasserted, and Asserted can output up to four of these signals at once. The Pixel Clock signal is only supported by the PXI-1408.

Note: The restriction of outputting no more than four signals at once applies to the other functions as well.

IMAQ Generate Pulse—This function allows you to generate a hardware timed pulse or pulse train from the IMAQ device and drive two pulses at once. You can choose to trigger the pulse from an internal signal, an external signal from RTSI or the External Trigger lines, or you can configure the software to start it immediately.

IMAQ Trigger Read—This function allows you to read the status of External Trigger lines or RTSI lines. IMAQ devices allow read/write access to any four of the available seven RTSI lines at a time.

IMAQ Configure Trigger—This function allows you to base your acquisition off an external trigger from the External Trigger lines or RTSI. You can configure one trigger for each IMAQ device. The following triggering modes are supported:
• Start of Acquisition allows you to wait for a trigger pulse before acquiring images. When the trigger is received, the acquisition captures the next full frame after the trigger and proceeds as normal after the trigger.
• Trigger Each Buffer requires a separate trigger pulse for each image acquired.
• Trigger Buffer List applies to ring acquisitions that are a multiple buffer acquisition. When a trigger is received, all the buffers acquire their images and, instead of starting over and continuously acquiring, the acquisition waits for the next trigger to fill all the buffers with new images.
• Trigger Each Line is used with line scan cameras and allows each trigger to acquire an individual line from a line scan camera. Trigger Each Line is useful for coordinating the acquisition with a conveyor belt encoder; if the conveyor belt slows down or speeds up, the acquisition follows accordingly. If you use this trigger mode, you can also use Trigger Each Buffer or Trigger Start of Acquisition.

PXI System Reference Clock
The PXI-1422 devices do not use the 10 MHz system reference clock. All synchronization functionality is instead implemented on the PXI trigger bus using RTSI.

Implementation of Signal Routing using NI-IMAQ
Signal routing to the PXI backplane is implemented programmatically using functions in NI-IMAQ, the National Instruments IMAQ driver. Table 3 outlines the NI-IMAQ functions supported by the PXI-1422 that help route the signals to the backplane and configuring triggers.


Listed below under Related Links are links to Common Applications, Online Documentation, and Example Programs.

Related Links:
Vision – Acquisition Analysis Image I/O Image Processing
Image Acquisition Tutorial
KnowledgeBase 1XAEEJL4 – Why Can’t I Genereate a Pulse Train or Retriggered Pulses with the PCI/PXI-1422 1424?
KnowledgeBase 1JHGCJ6Y – What is the Start Up State for Trigger Lines of the PCI-1422/1424?
NI 1422 User Manual
NI-IMAQ Online Functions Reference Manual
Synchronizing Motion, Vision, and Data Acquisition

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