Appendix A DeviceNet Overview
NI-DNET User Manual A-2 ni.com
Physical Characteristics of DeviceNet
The following list summarizes the physical characteristics of DeviceNet.
• Trunkline-dropline cabling—main trunk cable with a drop cable for
each device
• Selectable baud rates of 125 K, 250 K, and 500 K
• Support for up to 64 devices—each device identifies itself using a
MACID (Media Access Control Identifier) from 0–63
• Device removal/insertion without severing the network
• Simultaneous support for both network-powered and self-powered
devices
• Various connector styles
For complete information on how to connect your National Instruments
hardware onto the DeviceNet network, refer to your getting started manual.
General Object Modeling Concepts
The DeviceNet Specification uses object-oriented modeling to describe the
behavior of different components in a device, how those components relate
to one another, and how network communication takes place. The
following paragraphs briefly describe object-oriented modeling and how
these concepts are used within the DeviceNet Specification.
In object-oriented terminology, a classification of components with similar
qualities is called a class. For example, different classes of geometric
shapes could include squares, circles, and triangles. Figure A-1 shows
various classes and instances of geometric shapes.
Table A-1. DeviceNet Baud Rates and Wiring Lengths
Baud
Rate
Trunk
Length
Drop Length
Maximum
Drop Length
Cumulative
125 Kb/s 500 m (1640 ft) 6 m (20 ft) 156 m (512 ft)
250 Kb/s 250 m (820 ft) 6 m (20 ft) 78 m (256 ft)
500 Kb/s 100 m (328 ft) 6 m (20 ft) 39 m (128 ft)