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Chapter 2
Using Your 653X
653X User Manual
data is in the buffer, transfer stops. If the stop trigger arrives before all the
pretrigger data is acquired, NI-DAQ returns an error.
STOPTRIG
REQ
Figure 2-9. Stopping Data Transfer Using a Trigger
Start and Stop Trigger
When using a start and stop trigger, transfer starts upon receiving a trigger
on the start trigger line (ACK/STARTTRIG pin) and ends upon receiving
a trigger on the stop trigger line (STOPTRIG pin) and a predetermined
amount of pretrigger and posttrigger data is saved in the buffer. If a stop
trigger is received before a start trigger, it is ignored. If the stop trigger
arrives before all the pretrigger data is acquired, NI-DAQ returns an error.
ACK (STARTTRIG)
STOPTRIG
REQ
Figure 2-10. Using a Start and Stop Trigger
Pattern-Matching Trigger (Input Only)
Instead of using an external signal on the start/stop trigger pins on the
I/O connector, you may start or stop (not both) an operation once a
user-specified digital pattern is matched or not matched.
Specify four parameters to set up a pattern-matching trigger:
•
Whether it is a start or stop trigger
•
The data pattern to be detected/matched
•
The mask, which selects the bits of interest for pattern comparison
(0 for bits not of interest)
Pretrigger Data
Pretrigger Data
2-20
Posttrigger Data
Posttrigger Data
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