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

Chapter 2 Digital I/O
NI PCI-8254R User Manual 2-6 ni.com
When the pulse generator is configured for a particular trigger input, after
generating a pulse, it waits for another trigger before generating another
pulse. When the pulse generator is configured to immediately generate the
pulse on a software start, after generating a pulse, it immediately generates
another pulse.
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. 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. 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.
The following figure shows an output pulse when a trigger is selected.
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