National Instruments DAQ PCI E Series User Manual

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National Instruments DAQ PCI E Series User Manual Manual pdf 74 page image

Chapter 4 Signal Connections©National Instruments Corporation4-31PCI E Series User ManualFigures 4-16 and 4-17 show the input and output timing requirementsfor the TRIG1 signal.Figure 4-16. TRIG1 Input Signal TimingFigure 4-17. TRIG1 Output Signal TimingThe board also uses the TRIG1 signal to initiate pretriggered DAQoperations. In most pretriggered applications, the TRIG1 signal isgenerated by a software trigger. Refer to the TRIG2 signal descriptionfor a complete description of the use of TRIG1 and TRIG2 in apretriggered DAQ operation.TRIG2 SignalAny PFI pin can externally input the TRIG2 signal, which is availableas an output on the PFI1/TRIG2 pin. Refer to Figure 4-13 for therelationship of TRIG2 to the DAQ sequence.As an input, the TRIG2 signal is configured in the edge-detection mode.You can select any PFI pin as the source for TRIG2 and configure thepolarity selection for either rising or falling edge. The selected edge ofthe TRIG2 signal initiates the posttriggered phase of a pretriggeredacquisition sequence. In pretriggered mode, the TRIG1 signal initiatesthe data acquisition. The scan counter indicates the minimum numberRising-edgepolarityFalling-edgepolarityt wt w = 10 ns minimumt wt w = 50-100 ns