Chapter 4
Connecting Signals
4-22
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Pretriggered data acquisition allows you to view data that is acquired before
the trigger of interest in addition to data acquired after the trigger.
Figure 4-12 shows a typical pretriggered DAQ sequence. The description
for each signal shown in these figures is included later in this chapter.
Figure 4-12.
Typical Pretriggered Acquisition
TRIG1 Signal
Any PFI pin can externally input the TRIG1 signal, which is available as
an output on the PFI0/TRIG1 pin.
Refer to Figures 4-11 and 4-12 for the relationship of TRIG1 to the DAQ
sequence.
As an input, TRIG1 is configured in the edge-detection mode. You can
select any PFI pin as the source for TRIG1 and configure the polarity
selection for either rising or falling edge. The selected edge of TRIG1 starts
the DAQ sequence for both posttriggered and pretriggered acquisitions.
As an output, TRIG1 reflects the action that initiates a DAQ sequence, even
if the acquisition is being externally triggered by another PFI. The output is
an active high pulse with a pulse width of 50 to 100 ns. This output is set to
high-impedance at startup.
n/a
0
1
2
3
1
0
2
2
2
TRIG1
TRIG2
STARTSCAN
CONVERT*
Scan Counter
