Chapter4 SignalConnections
©NationalInstruments Corporation 4-35 6023E/6024E/6025EUser Manual
Figure4-22. TRIG1Output Signal Timing
The devicealso uses the TRIG1 signal to initiate pretriggered DAQ
operations. In most pretriggered applications, the TRIG1 signal is
generated bya software trigger. Refer to the TRIG2 signal description for
acomplete description of the use of TRIG1 and TRIG2 in a pretriggered
DAQoperation.
TRIG2 Signal
Any PFIpin can externally input the TRIG2 signal, which is available as
anoutput on the PFI1/TRIG2 pin. RefertoFigure 4-18for the relationship
ofTRIG2 to the D AQ sequence.
As aninput, the TRIG2 signal is configured in the edge-detection mode.
Youcan select any PFI pin as the source for TRIG2 and configure the
polarityselection f or either rising or falling edge. The selected edge of the
TRIG2signal initiates the posttriggered phase of a pretriggered acquisi tion
sequence. In pretriggered mode, the TRIG1 signal initiates the data
acquisition. The scan counter indicates the minimum number of scans
before TRIG2 can berecognized. A fter the scan counter decrements to
zero,it is loaded with the number of posttrigger scans to acquire while the
acquisitioncontinue s. The deviceignores the TRIG2 signal if it is asserted
priort o the scancounter decrementing to zero. After the selected edge of
TRIG2 is received,the device acquires a fixed number of scans and the
acquisitionstops. This mode acquires data both beforeand after receiving
TRIG2.
As ano utput, the TRIG2 signal reflects the posttrigger in a pretriggered
acquisition sequence. This is true evenif the acquisition is externally
triggered byanother PFI. The TRIG2 signal is not used in posttriggered
data acquisition. The output is an activehigh pulse with a pulse width of
50to 100 ns. This output is set to high impedance at startup.
tw
tw=50-100 ns