Chapter 2
NI 5450 Overview
©
National Instruments Corporation
2-83
NI PXIe-5450 User Manual
Marker Events
A marker is an event that the device generates in relation to a waveform that
is generated. The event is configured to occur at the time that a specific
location or sample
n
in the waveform generates on the CH 0 connector. If
the waveform loops multiple times in a segment, the marker generates each
time the waveform loops. The following figure shows a pulse that
represents a waveform sample
n
that is one Sample clock in width of a
waveform being generated on the CH 0 connector. The second pulse, the
Marker event, represents the pulse that generates when the corresponding
waveform sample
n
outputs at the CH 0 connector.
t
m1
represents the delay in time of the Marker event generated relative to the
configured waveform sample
n
being generated.
t
m2
represents the Marker event pulse width in time.
NI-FGEN takes into account the factors that affect the delays in the Digital
and Analog paths in assuring that the Marker event appears within one
Sample clock of the waveform output. Therefore, t
m1
is less than one
Sample clock period.
The Marker event pulse width, t
m2
, is at least 150 ns and can be
significantly longer than 150 ns for slower Sample clocks. You can
configure the pulse width by setting the Marker Event Pulse Width
property or the
NIFGEN_ATTR_MARKER_EVENT_PULSE_WIDTH
attribute.
Instruments commonly have a minimum pulse width specification for a
trigger to be registered, and trigger pulses of smaller width are ignored. The
signal generator ensures that a minimum pulse width exists on the Marker
event by using a pulse stretching circuit. A Sample clock rate of 100 MS/s
W
a
veform
Sa
mple
n
t
m2
t
m1
M
a
rker Event
W
a
veform O
u
tp
u
t
on CH 0
