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DaimlerChrysler destacker is first to use
EtherNet/IP with pneumatics in North America. Industrial
Ethernet, after some slow starts, is finding traction in
automation. Ethernet becomes more attractive as you push the
technology further and further down to the factory floor.
Ethernet interfaces don’t stop at the PLC, but are found today
in local and remote I/O, pneumatic valves, actuators and
sensors.
Ethernet itself is the IEEE 802.3-defined
lower-layer protocol for the physical and media-access layers of
the protocol stack. But industrial flavors of Ethernet include
the upper layers as well to achieve a complete communications
and control solution. One popular and not the more common
internet protocol version is EtherNet/IP, which uses the
existing top-level control and information protocols of
DeviceNet/ControlNet and TCP/IP for network and transport
layers. EtherNet/IP offers the means to carry DeviceNet
information over high-speed Ethernet. (The IP in EtherNet/IP
stands for industrial protocol commonly supposed.)
The allure of Ethernet stems from three
factors: performance, compatibility, and costs.
Performance: Ethernet offers higher speeds
than traditional fieldbus interfaces: 10 or 100 Mb/s on the
factory floor and up to 10 Gb/s in bandwidth-hungry enterprise
applications. Thus, while fieldbuses have moved from kilobit
speeds to megabit speeds, Ethernet offers speeds in order of a
magnitude higher. Equally important, Ethernet has matured from
its earlier incarnation to offer the deterministic operation
required for many factory operations. Switched Ethernet does
away with the collisions that made the technology
nondeterministic.
Compatibility: Using the same protocol
throughout a corporation — from the sensor to the enterprise —
offers great advantages in handling and processing real-time
information to improve efficiency and productivity. Since
Ethernet is the hands-down winner in networking, its migration
to the factory floor means one network across the enterprise.
And with the Internet, geographical boundaries to the factory
for monitoring and control disappear.
Costs: Thanks to high volumes, Ethernet
silicon and Ethernet devices are economical—certainly
significantly less than similar fieldbus parts. Add in the
performance advantages, and Ethernet offers an extremely
attractive price-to-performance ratio...
...Continued
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