National Instruments 653X - Manual (Page 38)

Chapter 2 Using Your 653X
653X User Manual 2-20 ni.com
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
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.
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)
REQ
STOPTRIG
Pretrigger Data Posttrigger Data
REQ
STOPTRIG
ACK (STARTTRIG)
Pretrigger Data Posttrigger Data