National Instruments NI VISION PCI-8254R - Manual (Page 17)

Chapter 2 Hardware Overview
NI PCI-8254R User Manual 2-6 ni.com
If the trigger input is set to Immediate in LabVIEW or using a None status
signal in C and Visual Basic, the pulse generation occurs as soon as the
pulse mode is set to Start in LabVIEW or imaqIOPulseStart in C and
Visual Basic. After generating a pulse, it immediately generates another
pulse until the pulse generation is stopped. If the trigger input is set to one
of the hardware trigger inputs, the timed pulse output waits for an assertion
edge on the appropriate trigger input. After generating a pulse it waits for
another trigger before generating another pulse. The assertion edge is
configurable based on the trigger polarity parameter. It then generates one
pulse and rearms to wait for the next trigger. In either case, the pulse output
generation stops and resets if the pulse mode parameter is set to Stop in
LabVIEW or imaqIOPulseStop in C and Visual Basic.
Figure 2-1 shows an output pulse when a trigger is selected.
Figure 2-1. Output pulse resulting from trigger selection
Pulse Modes
Each pulse generator has a Start, Single Shot, and Stop mode. Configure
the pulse generator when in Stop mode. Then, set the pulse generator to
Start mode for continuous or rearmed pulses, and set it to Single Shot for a
pulse that should assert only once.
Pulse Delay
Pulse delay is the amount of time between a trigger and the first (assertion)
edge of an output pulse. The pulse delay is configurable in units of
microseconds or quadrature encoder counts. If configured for
microseconds, available values are between 1 µs and 4,294,967,295 µs,
which is 4,294 seconds, or approximately 71 minutes. If the delay is
configured for quadrature encoder counts, the range of choices is 0 counts
to 4,294,967,295 counts.
Output
Pulse
Trigger
Input