Chapter 2
NI 5450 Overview
NI PXIe-5450 User Manual
2-62
ni.com
In some cases at high Sample clocks, your script may result in an underflow
error. Underflow errors in a script can be created by waveform size, marker
placement, and specific script instructions. To avoid underflow errors, refer
to the minimum waveform size in your device specifications.
Aborting Generation
You can abort the generation of the current waveform. Aborting the
generation exhibits different behaviors for different waveform output
modes.
Sample Size and Resolution
The NI 5450 stores arbitrary waveforms in memory as signed 16-bit digital
words. On the NI 5450, the entire 16 bits are sent to the digital gain circuit,
the OSP and the DAC.
Waveform Size and Quantum
The NI 5450 onboard memory architecture imposes certain requirements
on the waveform size and quantum.
Waveform Size
The minimum waveform size on the NI 5450 depends on the output mode
and the trigger mode. Refer to the device specifications for the minimum
waveform size values for the different modes.
Note
To provide greater programming flexibility, NI-FGEN does not strictly enforce the
minimum waveform sizes stated in the device specifications. NI-FGEN enforces a
minimum waveform size of four samples for all trigger modes (two if the OSP block is
enabled and the waveform data points have been configured for complex data using the
Data Processing Mode property or the
NIFGEN_ATTR_OSP_DATA_PROCESSING_MODE
attribute), so it is possible to generate waveforms that are smaller than the sizes given in
the specifications. However, the device may not be able to fetch data from onboard memory
fast enough to keep up with waveform generation at high sample rates.
This condition may occur if a segment is looping over a very small waveform, if a segment
is generating a marker within a very small waveform, or if triggers are advancing the
segments in a sequence very rapidly. When this occurs, NI-FGEN reports
Error
–1074115901 (0xBFFA4AC3): Device Data Underflow
.
The simplest way to avoid this condition is to follow the minimum waveform size
guidelines in the specifications. If these rules are followed, a data underflow error will not
