National Instruments 653X - Manual (Page 46)

Chapter 2 Using Your 653X
653X User Manual 2-28 ni.com
The three types of trigger signals available are the start trigger, the stop
trigger, or the start and stop trigger.
Start Trigger
A start trigger is a trigger that initiates a pattern I/O upon receipt of a
hardware trigger on the ACK (STARTTRIG) pin.
Figure 2-16. Starting Data Transfer Using a Trigger
Stop Trigger
When using a stop trigger, transfer starts upon a software command. 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 an error will return in software.
Figure 2-17. 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 an error will return in
software.
REQ
ACK (STARTTRIG)
Posttrigger Data
REQ
STOPTRIG
Pretrigger Data Posttrigger Data