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data is in the buffer, transfer stops. If the stop trigger arrives before all the 
pretrigger data is acquired, NI-DAQ returns an error.

Figure 2-9.  Stopping Data Transfer Using a 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.

Figure 2-10.  Using a Start and Stop Trigger

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)

REQ

STOPTRIG

Pretrigger Data

Posttrigger Data

REQ

STOPTRIG

ACK (STARTTRIG)

Pretrigger Data

Posttrigger Data