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Signal Name
PFI3/GPCTR1_SOURCE
PFI4/GPCTR1_GATE
GPCTR1_OUT
PFI5/UPDATE*
PFI6/WFTRIG
PFI7/STARTSCAN
PFI8/GPCTR0_SOURCE
PFI9/GPCTR0_GATE
GPCTR0_OUT
FREQ_OUT
pu = pull up; pd = pull down; DO = Digital Output
The tolerance on the 50 kΩ pull-up and pull-down resistors is very large. Actual value may range between 17 and 100 kΩ.
Types of Signal Sources
Floating Signal Sources
© National Instruments Corporation
Table 4-5. Digital I/O Signal Summary (Continued)
Signal
Impedance
Type and
Input/
Direction
Output
DIO
—
DIO
—
DO
—
DIO
—
DIO
—
DIO
—
DIO
—
DIO
—
DIO
—
DO
—
When making signal connections, you must first determine whether the
signal sources are floating or ground-referenced. The following sections
describe these two types of signals.
A floating signal source is not connected in any way to the building ground
system but, rather, has an isolated ground-reference point. Some examples
of floating signal sources are outputs of transformers, thermocouples,
battery-powered devices, optical isolator outputs, and isolation amplifiers.
An instrument or device that has an isolated output is a floating signal
Protection
(Volts)
Source
On/Off
(mA at V)
V
+0.5
3.5 at
CC
(V
–0.4)
CC
V
+0.5
3.5 at
CC
(V
–0.4)
CC
—
3.5 at
(V
–0.4)
CC
V
+0.5
3.5 at
CC
(V
–0.4)
CC
V
+0.5
3.5 at
CC
(V
–0.4)
CC
V
+0.5
3.5 at
CC
(V
–0.4)
CC
V
+0.5
3.5 at
CC
(V
–0.4)
CC
V
+0.5
3.5 at
CC
(V
–0.4)
CC
V
+0.5
3.5 at
CC
(V
–0.4)
CC
—
3.5 at
(V
–0.4)
CC
4-7
Chapter 4
Connecting Signals
Rise
Sink
Time
(mA at V)
(ns)
Bias
5 at 0.4
1.5
50 kΩ
pu
5 at 0.4
1.5
50 kΩ
pu
5 at 0.4
1.5
50 kΩ
pu
5 at 0.4
1.5
50 kΩ
pu
5 at 0.4
1.5
50 kΩ
pu
5 at 0.4
1.5
50 kΩ
pu
5 at 0.4
1.5
50 kΩ
pu
5 at 0.4
1.5
50 kΩ
pu
5 at 0.4
1.5
50 kΩ
pu
5 at 0.4
1.5
50 kΩ
pu
NI 6115/6120 User Manual
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