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PCI-DAS6013 and PCI-DAS6014 User's Guide
Functional Details
The A/D START TRIGGER signal is also used to initiate pre-triggered DAQ operations
(when you need to acquire data just before a trigger event). In most pre-triggered
applications, the A/D START TRIGGER signal is generated by a software trigger. The
use of A/D START TRIGGER and A/D STOP TRIGGER in pre-triggered DAQ
applications is explained next.
A/D STOP TRIGGER signal
Pre-triggered data acquisition continually acquires data into a circular buffer until a
specified number of samples have been collected after the trigger event.
Figure 4-6
illustrates a typical pre-triggered DAQ sequence.
A/D Start Trigger
Don't care
A/D Stop Trigger
Start Scan
Convert
Scan Counter
3
2
1
0
3
2
1
0
3
2
1
Figure 4-6. Pre-triggered Data Acquisition Example
The A/D STOP TRIGGER signal signifies when the circular buffer should stop and
when the specified number of post trigger samples should be acquired. It is available as
an output and an input. By default, it is available at AUXIN2 as an input but may be
programmed for access at any of the AUXIN pins. It may be programmed for access at
any of the AUXOUT pins as an output.
When using the A/D STOP TRIGGER signal as an input, the polarity may be configured
for either rising or falling edge. The selected edge of the A/D STOP TRIGGER signal
initiates the post-triggered phase of a pre-triggered acquisition sequence.
As an output, the A/D STOP TRIGGER signal indicates the event separating the
pre-trigger data from the post-trigger data. The output is an active high pulse with a
pulse width of 50 ns.
Figure 4-7
and
Figure 4-8
show the input and output timing
requirements for the A/D STOP TRIGGER signal.
4-6
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