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Appendix A Connecting I/O Signals © National Instruments Corporation A-5 Mult ifunction Reconfigurable I/O User Manual Caution Connectio ns that exceed any of the maximum ratings of input or output signals on the NI 78 x…
Appendix A Connecting I/O Signals
Multifunction Reconfigurable I/O User Manual A-4 ni.com
To access the signals on the I/O connectors, you must connect a cable from
the I/O connector to a signal accessory. Plug the small VHDCI connector
end of the cable into the appropriate I/O connector and connect the other
end of the cable to the appropriate signal accessory.
Table A-1. I/O Connector Signal Descriptions
Signal Name Reference Direction Description
+5V DGND Output +5 VDC Source—These pins supply 5 V from the computer
power supply. For more information on the +5V terminals,
refer to the +5 V Power Source section in Chapter 2,
Hardware Overview of the NI 78xx.
Analog Signals (NI 783x/784x/785x Only)
AI<0..7>+ AIGND Input Positive input for Analog Input channels 0 through 7.
AI<0..7>– AIGND Input Negative input for Analog Input channels 0 through 7.
AIGND — — Analog Input Ground—These pins are the reference point
for single-ended measurements in RSE configuration and
the bias current return point for differential measurements.
All three ground references—AIGND, AOGND, and
DGND—are connected to each other on the
NI 783x/784x/785x.
AISENSE AIGND Input Analog Input Sense—This pin serves as the reference node
for AI <0..7> when the device is configured for NRSE mode.
AO<0..7> AOGND Output Analog Output channels 0 through 7. Each channel can
source or sink up to 2.5 mA.
AOGND — — Analog Output Ground—The analog output voltages
are referenced to this node. All three ground
references—AIGND, AOGND, and DGND—are
connected to each other on the NI 783x/784x/785x.
Digital Signals (All NI 78xx Devices)
DGND — — Digital Ground—These pins supply the reference for the
digital signals at the I/O connector and the 5 V supply.
All three ground references—AIGND, AOGND, and
DGND—are connected to each other on the
NI 783x/784x/785x.
DIO<0..39>
Connector <0..3>
(NI 781x)
DIO<0..15>
Connector 0
(NI 783x/784x/785x)
DIO<0..39>
Connector <1..2>
(NI 783x/784x/785x)
DGND Input or
Output
Digital I/O signals.
Appendix A Connecting I/O Signals
© National Instruments Corporation A-5 Multifunction Reconfigurable I/O User Manual
Caution Connections that exceed any of the maximum ratings of input or output signals
on the NI 78xx can damage the NI 78xx and the computer. Maximum input ratings for each
signal are in the Protection column of Table A-2. NI is not liable for any damage resulting
from such signal connections
Table A-2. NI 78xx I/O Signal Summary
Signal Name
Signal
Type and
Direction
Impedance
Input/
Output
Protection
(Volts)
On/Off
Source
(mA at V)
Sink
(mA at V)
Rise Time Bias
+5V DO — — — — — —
Analog Signals (NI 783x/784x/785x Only)
AI<0..7>+ AI 10 GΩ in
parallel with
100 pF
42/35 — — — ±2 nA
AI<0..7>– AI 10 GΩ in
parallel with
100 pF
42/35 — — — ±2 nA
AIGND AO — — — — — —
AISENSE AI 10 GΩ in
parallel with
100 pF
42/35 — — — ±2 nA
AO<0..7> AO 1.25 Ω Short
circuit to
ground
2.5 at 10 2.5 at –10 10 V/μs —
AOGND AO — — — — — —
Digital Signals (All NI 78xx Devices) — — — —
DIO<0..39>
Connector <0..3>
(NI 781x)
DIO<0..15>
Connector 0
(NI 783x,
NI 784x, and
NI 785x)
DIO<0..39>
Connector <1..2>
(NI 783x,
NI 784x, and
NI 785x)
DIO — –0.5 to +7.0
(NI 783x)
–20 to 20
(NI 784x/
NI 785x)
4.0 at 2.4 4.0 at 0.4 — —
AI = Analog Input AO = Analog Output DIO = Digital Input/Output DO = Digital Output
Appendix A Connecting I/O Signals
Multifunction Reconfigurable I/O User Manual A-6 ni.com
Connecting to 5B and SSR Analog Signal Conditioning
(NI 783x /784x /785x Only)
NI provides cables that allow you to connect signals from the
NI 783x/784x/785x directly to 5B backplanes for analog signal
conditioning and SSR backplanes for digital signal conditioning.
The NSC68-262650 cable connects the signals on the NI 783x/784x/785x
RMIO connector directly to 5B and SSR backplanes. This cable has a
68-pin male VHDCI connector on one end that plugs into the
NI 783x/784x/785x RMIO connector. The other end of this cable provides
two 26-pin female headers plus one 50-pin female header.
One of the 26-pin headers contains all the NI 783x/784x/785x analog input
signals. You can plug this connector directly into a 5B backplane for analog
input signal conditioning. The NI 783x/784x/785x AI<0..n> correspond to
the 5B backplane channels <0..n> in sequential order. Configure the AI
channels to use the NRSE input mode when using 5B signal conditioning.
The other 26-pin header contains all the NI 783x/784x/785x analog output
signals. You can plug this connector directly into a 5B backplane for AO
signal conditioning. The NI 783x/784x/785x AO<0..n> correspond to the
5B backplane channels <0..n> in sequential order.
The 50-pin header contains the 16 DIO lines available on the
NI 783x/784x/785x RMIO connector. You can plug this header directly into
an SSR backplane for digital signal conditioning. DIO lines <0..15>
correspond to the 5B backplane Slots <0..15> in sequential order.
The 5B connector pinouts are compatible with 8-channel 5B08 backplanes
and 16-channel 5B01 backplanes. The NI 7830 can accept analog
input from the first four channels of a 16-channel backplane.
The NI 7831/7833/784x/785x can accept analog input from the
first eight channels of a 16-channel backplane. The SSR connector pinout
is compatible with 8-, 16-, 24-, and 32-channel SSR backplanes. You can
connect to an SSR backplane containing a number of channels unequal to
the 16 DIO lines available on the 50-pin header. In this case, you have
access to only the channels that exist on both the SSR backplane and the
NSC68-262650 cable 50-pin header.