Chapter 4
Connecting Signals
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National Instruments Corporation
4-21
As an input, each PFI pin can be individually configured for edge or level
detection and for polarity selection. You can use the polarity selection for
any of the timing signals, but the edge or level detection depends upon the
particular timing signal being controlled. The detection requirements for
each timing signal are listed within the section that discusses that individual
signal.
In edge-detection mode, the minimum pulse width required is 10 ns. This
applies for both rising-edge and falling-edge polarity settings. There is no
maximum pulse-width requirement in edge-detect mode.
In level-detection mode, there are no minimum or maximum pulse-width
requirements imposed by the PFIs themselves, but there may be limits
imposed by the particular timing signal being controlled. These
requirements are listed later in this chapter.
DAQ Timing Connections
The DAQ timing signals are TRIG1, TRIG2, STARTSCAN, CONVERT*,
AIGATE, SISOURCE, SCANCLK, and EXTSTROBE*.
Posttriggered data acquisition allows you to view only data that is acquired
after a trigger event is received. A typical posttriggered DAQ sequence is
shown in Figure 4-11.
Figure 4-11.
Typical Posttriggered Acquisition
1
3
0
4
2
TRIG1
STARTSCAN
CONVERT*
Scan Counter
