Chapter 7
PFI
7-2
ni.com
Fig
u
re 7-2 shows the circ
u
itry of an o
u
tp
u
t PFI line.
Figure 7-2.
USB-621
x
PFI Output Circuitry
When a terminal is
u
sed as a timing inp
u
t or o
u
tp
u
t signal, it is called PFI
x.
When a terminal is
u
sed as a static digital inp
u
t or o
u
tp
u
t, it is called P0.
x
,
P1.
x
, or P2.
x
.
The voltage inp
u
t and o
u
tp
u
t levels and the c
u
rrent drive levels of the PFI
signals are listed in the
NI USB-621x Specifications
.
Using PFI Terminals as Timing Input Signals
Use PFI terminals to ro
u
te external timing signals to many different
USB-621
x
f
u
nctions. Each inp
u
t PFI terminal can be ro
u
ted to any of the
following signals:
•
AI Convert Clock (ai/ConvertClock)
•
AI Sample Clock (ai/SampleClock)
•
AI Start Trigger (ai/StartTrigger)
•
AI Reference Trigger (ai/ReferenceTrigger)
•
AI Pa
u
se Trigger (ai/Pa
u
seTrigger)
•
AI Sample Clock Timebase (ai/SampleClockTimebase)
•
AO Start Trigger (ao/StartTrigger)
•
AO Sample Clock (ao/SampleClock)
Timing
S
ign
a
l
s
Direction Control
I/O Protection
47 k
Ω
P
u
ll-Down
PFI/DIO Pin
S
t
a
tic DO
B
u
ffer
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
