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Issue
98, September 1998
Networking
with DeviceNet
by
Jim Brady
With
all the debate on networks these days, it’s easy to get
confused about the differences between networks, buses,
and field buses, particularly when a new technology comes
along. Join Jim for the lowdown on DeviceNet.
Start
• Sorting Them Out
• New
Breed •
Motivation •
Can •
Message Reliability •
DeviceNet Connections •
Device Net Messages •
Stringing Messages Together •
Some Real Messages •
Object Library •
Conformance Testing •
DeviceNet Standards •
References,Sources,PDF
Leading articles on networks raises a lot of questions—like whether
to call DeviceNet a network, a bus, a fieldbus, or what?
The
term "bus" is used for industrial networks that
control things, as opposed to general office networks
that move data. I decided to forget about impressive terms
and stick to basics. I want to cover the meat and potatoes
of what a developer needs to know to implement a DeviceNet
network.
Why
are there so many network protocols? Figure 1
shows 15 of them. Why not just use Ethernet?
In
the beginning, I didn’t ask. I developed DeviceNet
interfaces because customers requested them. Then Profibus,
then others. However, with time, I wondered: is there
an ideal network for a given application?
This
month, I show how DeviceNet compares to other device networks
and explain how it works. In Part 2, I’ll look at
a real DeviceNet device, code and all.
Better
dust off your C++ books because DeviceNet is object oriented
all the way. C works, but C++ fits like a glove.
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