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Chapter 4 Signal Connections
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National Instruments Corporation 4-21 PCI-6110E/6111E User Manual
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 board 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 board will acquire a
fixed number of scans and the acquisition will stop. 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 25 to 50 ns. This output is set to tri-state at startup.
Figures 4-14 and 4-15 show the input and output timing requirements
for the TRIG2 signal.
Figure 4-14. TRIG2 Input Signal Timing
Figure 4-15. TRIG2 Output Signal Timing
Rising-edge
polarity
Falling-edge
polarity
t
w
t
w
= 10 ns minimum
t
w
t
w
= 25-50 ns
PCI_E.book Page 21 Thursday, June 25, 1998 12:55 PM