Chapter 2
Using Your NI 653X
©
National Instruments Corporation
2-9
Figure 2-3.
Starting Data Transfer Using a Trigger
Stop Trigger
When you use a stop trigger, data transfer starts upon a software command.
Then, once a hardware trigger is received on the STOPTRIG pin, a
predetermined amount of pretrigger and posttrigger data is saved in the
buffer. Once this 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 2-4.
Stopping Data Transfer Using a Trigger
Start and Stop Trigger
When you use a start and stop trigger, data 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 the device receives a stop trigger before a start trigger, the stop
trigger is ignored. If the stop trigger arrives before all the pretrigger data is
acquired, NI-DAQ returns an error.
REQ
ACK (STARTTRIG)
Posttrigger Data
REQ
STOPTRIG
Pretrigger Data
Posttrigger Data