Digital I/O Overview
Digital input/output (DIO) devices are used in a wide variety of ER-8 and ER-16 accessories and eight channel SC-2062 enclosure are
applications from automotive design, industrial factory automation, available. Refer to Table 3 for signal conditioning accessory catalog
and machine control, to aerospace, laboratory research, and page numbers.
Product Families
biomedical applications. You can connect NI digital I/O devices to
NI 653x
High-Speed
DIO (p.432)
✓
NI 6527
Isolated
DIO (p. 377)
✓
NI 650x
Low-Cost
DIO (p. 379)
✓
limit and proximity switches, photoelectric sensors, level gauges,
pressure switches, gas detectors, pumps, motors, solid-state relays,
electromechanical relays, digital data buses, and more.
Application
Perform basic digital I/O
Mode of Operation
Software
timed
Transfer data with fixed
timing between points
Transfer data where both
the device under test and
measurement device can
pause the transfer
Run a user-defined software Change Notification
routine when a user-defined and Pattern Matching
DIO event occurs
Hardware
timed
Handshaking
I/O
✓
✓
–
–
–
NI DIO devices can be installed in traditional desktop computers
using the PCI or ISA bus, connected via USB port, or installed in laptop
computers with PCMCIA slots. For the utmost in reliability and
mechanical ruggedness, NI also offers PXI digital I/O devices suitable for
operation in the LabVIEW Real-Time environment.
1
✓
✓
✓
✓
1Handshaking supplied by the 8255; only one handshaking mode is available. See individual product details on the following
pages for more information. See page 376 for details.
Choose Your Digital I/O Hardware
Isolation
Isolation physically and electrically separates two parts of a circuit
and provides several advantages. It breaks ground loops, improves
common-mode voltage and noise rejection, and it permits two
Table 2. Digital I/O Applications.
parts of the circuit to be at different voltage levels. Isolation Tech Tip
protects both computer circuitry and human operators. Industrial Q: I would like to perform high-speed buffered digital I/O controlled
applications often require isolation to protect the electronics from by an external or internal digital clock or handshaking signal. Which
transient voltage spikes and to provide greater common-mode noise digital I/O device do you recommend?
rejection in electrically noisy environments containing machinery
and inductive loads.
A: For high-speed buffered pattern I/O or handshaking I/O, see the
In the case of channel-to-channel isolated I/O, each channel has its hardware-timed NI 653x devices on page 432.
own ground terminal. In bank-to-bank isolated devices, each bank
Accessory
SCXI
Description
Page
(or group) consists of several channels that share the same ground
but are isolated from other banks. NI 6527 devices provide 60 VDC
of built-in channel-to-channel isolation between each I/O channel.
Signal conditioning system
Digital signal conditioning modules
Digital signal conditioning modules
Electromechanical relays
Configurable connector accessory
Shielded connector block
I/O connector block
I/O connector block
I/O connector block kit; includes cable
270
321
349
349
351
382
382
383
383
SSR Series
SC-206x
ER-8/16
CA-1000
SCB-100
CB-50
Signal Conditioning
For even higher isolation levels, NI 650x devices can be connected to
SCXI-116x signal conditioning modules to provide 450 Vrms of bank-
to-bank isolation. For lower channel counts, the SC-206x accessories
provide eight optically isolated inputs or outputs with 400 Vrms of
channel-to-channel isolation. Another option is SSR modules, which
provide 4000 Vrms of channel-to-channel isolation in 8, 16, 24, or
32-channel backplanes. For electromechanical relay outputs, the
CB-50LP
CB-100 kit
For complete and up-to-date information about accessories, visit ni.com/catalog
Table 3. Digital I/O Signal Conditioning Accessories.
Family
NI 6527
Product
PCI-6527
PXI-6527
Bus
PCI
PXI
Digital I/O Lines
24 inputs and
24 outputs
Logic Level
28 V input and
60 V output
Isolation
✓
Handshaking I/O1 Change Notification 8255 Chipset
Pattern Matching
Page
377
–
✓
–
–
NI 6507
NI 6508
PCI-DIO-96
PXI-6508
PC-DIO-96
PCI
PXI
ISA
USB
PCI
PCMCIA
ISA
96
5 V TTL/CMOS
–
✓
–
✓
✓
✓
379
379
DAQPad-6507/6508
NI 6503
PCI-6503
DAQCard-DIO-24
PC-DIO-24
24
5 V TTL/CMOS
–
✓
–
✓
1Handshaking supplied by the 8255; only one handshaking mode is available. See page 376 for details.
Table 1. Digital I/O Products Specifications Summary (See page 385 for detailed specifications.)
374 National Instruments • Tel: (800) 433-3488 • Fax: (512) 683-9300 • info@ni.com • ni.com
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