Chapter 4 Signal Connections
National Instruments Corporation
4-29
DAQCard E Series User Manual
TRIG2 Signal
Any PFI pin can externally input the TRIG2 signal, which is available
as an output on the PFI1/TRIG2 pin.
Refer to Figure 4-11 for the relationship of TRIG2 to the data
acquisition 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 the polarity selection for either rising or falling edge. The
selected edge of the TRIG2 signal initiates the posttriggered phase of a
pretriggered acquisition sequence. In pretriggered mode, the TRIG1
signal initiates the data acquisition. The scan counter indicates the
minimum number of scans before TRIG2 can be recognized. After the
scan counter decrements to zero, it is loaded with the number of
posttrigger scans to acquire while the acquisition continues. The
DAQCard ignores the TRIG2 signal if it is asserted prior to the scan
counter decrementing to zero. After the selected edge of TRIG2 is
received, the DAQCard acquires a fixed number of scans and the
acquisition stops. This mode acquires data both before and after
receiving TRIG2.
As an output, the TRIG2 signal reflects the posttrigger in a
pretriggered acquisition sequence. This is true even if the acquisition
is being externally triggered by another PFI. The TRIG2 signal is not
used in posttriggered data acquisition. The output is an active high
pulse with a pulse width of 50 to 100 ns. This signal is set to input
(High-Z) at startup.
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