©
National Instruments Corporation
5-1
5
Analog Output
Most USB-621
x
devices have analog o
u
tp
u
t f
u
nctionality. USB-621
x
devices that s
u
pport analog o
u
tp
u
t have two AO channels controlled
by a single clock and capable of waveform generation. Refer to the
NI USB-621x Specifications
for information abo
u
t yo
u
r device capabilities.
Fig
u
re 5-1 shows the analog o
u
tp
u
t circ
u
itry of USB-621
x
devices.
Figure 5-1.
USB-621
x
Analog Output Circuitry
The main blocks feat
u
red in the USB-621
x
analog o
u
tp
u
t circ
u
itry are as
follows:
•
DAC0 and DAC1
—Digital-to-analog converters (DACs) convert
digital codes to analog voltages.
•
AO FIFO
—The AO FIFO enables analog o
u
tp
u
t waveform
generation. It is a first-in-first-o
u
t (FIFO) memory b
u
ffer between the
comp
u
ter and the DACs. It allows yo
u
to download the points of a
waveform to yo
u
r USB-621
x
device witho
u
t host comp
u
ter
interaction.
AO
Sa
mple Clock
AO D
a
t
a
AO FIFO
AO 0
AO 1
DAC0
DAC1
I
s
ol
a
tion
B
a
rrier
(U
S
B-6215/
6216/6218
device
s
only)
Digit
a
l
I
s
ol
a
tor
s
