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Chapter 2 Hardware Overview of the NI 783xR
NI 783xR User Manual 2-16 ni.com
Connecting Digital I/O Signals
The DIO signals on the NI 783xR MIO connector are DGND and
DIO<0..15>. The DIO signals on the NI 783xR DIO connector are DGND
and DIO<0..39>. The DIO<0..n> signals make up the DIO port and DGND
is the ground reference signal for the DIO port. The NI 7830R has one MIO
and one DIO connector for a total of 56 DIO lines. The NI 7831R/7833R
has one MIO and two DIO connectors for a total of 96 DIO lines.
Refer to Figure B-1, NI 783xR Connector Locations, and Figure B-2,
NI 783xR I/O Connector Pin Assignments, for the connector locations and
the I/O connector pin assignments on the NI 783xR.
The DIO lines on the NI 783xR are TTL-compatible. When configured as
inputs, they can receive signals from 5 V TTL, 3.3 V LVTTL, 5 V CMOS,
and 3.3 V LVCMOS devices. When configured as outputs, they can send
signals to 5 V TTL, 3.3 V LVTTL, and 3.3 V LVCMOS devices. Because
the digital outputs provide a nominal output swing of 0 to 3.3 V
(3.3 V TTL), the DIO lines cannot drive 5 V CMOS logic levels.
To interface to 5 V CMOS devices, you must provide an external pull-up
resistor to 5 V. This resistor pulls up the 3.3 V digital output from the
NI 783xR to 5 V CMOS logic levels. Refer to Appendix A, Specifications,
for detailed DIO specifications.
Caution Exceeding the maximum input voltage ratings, listed in Table B-2, NI 783xR I/O
Signal Summary, can damage the NI 783xR and the computer. NI is not liable for any
damage resulting from such signal connections.
Caution Do not short the DIO lines of the NI 783xR directly to power or to ground. Doing
so can damage the NI 783xR by causing excessive current to flow through the DIO lines.
You can connect multiple NI 783xR digital output lines in parallel to
provide higher current sourcing or sinking capability. If you connect
multiple digital output lines in parallel, your application must drive all of
these lines simultaneously to the same value. If you connect digital lines
together and drive them to different values, excessive current can flow
through the DIO lines and damage the NI 783xR. Refer to Appendix A,
Specifications, for more information about DIO specifications. Figure 2-10
shows signal connections for three typical DIO applications.