National Instruments E Series User Manual

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National Instruments E Series User Manual Manual pdf 63 page image

Chapter 4 Signal ConnectionsNational Instruments Corporation4-27DAQCard E Series User ManualEXTSTROBE* SignalEXTSTROBE* is an output-only signal that generates either a singlepulse or a sequence of eight pulses in the hardware-strobe mode. Anexternal device can use this signal to latch signals or to trigger events.In the single-pulse mode, software controls the level of theEXTSTROBE* signal. A 10 and 1.2 μs clocks are available forgenerating a sequence of eight pulses in the hardware-strobe mode.Figure 4-13 shows the timing for the hardware-strobe modeEXTSTROBE* signal.TRIG1 SignalAny PFI pin can externally input the TRIG1 signal, which is availableas an output on the PFI0/TRIG1 pin.Refer to Figures 4-10 and 4-11 for the relationship of TRIG1 to thedata acquisition sequence.As an input, the TRIG1 signal is configured in the edge-detectionmode. You can select any PFI pin as the source for TRIG1 andconfigure the polarity selection for either rising or falling edge. Theselected edge of the TRIG1 signal starts the data acquisition sequencefor both posttriggered and pretriggered acquisitions. The DAQCardssupport analog triggering on the PFI0/TRIG1 pin. See Chapter 3 formore information on analog triggering.As an output, the TRIG1 signal reflects the action that initiates a dataacquisition sequence. This is true even if the acquisition is beingexternally triggered by another PFI. The output is an active high pulsewith a pulse width of 50 to 100 ns. This output is set to tri-state atstartup.Figure 4-13. EXTSTROBE* Signal Timingt w t wVOHVOLt w = 600 ns or 5 μs