National Instruments Data Acquisition Device NI USB-621x - Manual (Page 72)

© National Instruments Corporation 5-1 NI USB-621x User Manual
5
Analog Output
Most USB-621x devices have analog output functionality. USB-621x
devices that support analog output have two AO channels controlled
by a single clock and capable of waveform generation. Refer to the
NI USB-621x Specifications for information about your device capabilities.
Figure 5-1 shows the analog output circuitry of USB-621x devices.
Figure 5-1. USB-621x Analog Output Circuitry
The main blocks featured in the USB-621x analog output circuitry are as
follows:
• DAC0 and DAC1—Digital-to-analog converters (DACs) convert
digital codes to analog voltages.
• AO FIFO—The AO FIFO enables analog output waveform
generation. It is a first-in-first-out (FIFO) memory buffer between the
computer and the DACs. It allows you to download the points of a
waveform to your USB-621x device without host computer
interaction.
AO Sample Clock
AO Data AO FIFO
AO 0
AO 1
DAC0
DAC1
Isolation
Barrier
(USB-6215/
6216/6218
devices only)
Digital
Isolators