National Instruments NI 6238 - Manual (Page 53)

Chapter 5 Analog Output
NI 6238/6239 User Manual 5-2 ni.com
DACs. It allows you to download the points of a waveform to your M Series
device without host computer interaction.
AO Sample Clock
The AO Sample Clock signal reads a sample from the DAC FIFO and
generates the AO voltage.
Isolation Barrier and Digital Isolators
The digital isolators across the isolation barrier provide a ground break
between the isolated analog front end and the earth/chassis/building
ground.
Analog Output Data Generation Methods
When performing an analog output operation, you either can perform
software-timed or hardware-timed generations. Hardware-timed
generations can be non-buffered or buffered.
Software-Timed Generations
With a software-timed generation, software controls the rate at which data
is generated. Software sends a separate command to the hardware to initiate
each DAC conversion. In NI-DAQmx, software-timed generations are
referred to as on-demand timing. Software-timed generations are also
referred to as immediate or static operations. They are typically used for
writing a single value out, such as a constant DC current.
Hardware-Timed Generations
With a hardware-timed generation, a digital hardware signal controls the
rate of the generation. This signal can be generated internally on your
device or provided externally.
Hardware-timed generations have several advantages over software-timed
acquisitions:
• The time between samples can be much shorter.
• The timing between samples can be deterministic.
• Hardware-timed acquisitions can use hardware triggering.
Hardware-timed operations can be buffered or non-buffered. A buffer is a
temporary storage in computer memory for to-be-generated samples.