Industrial Ethernet

Industrial Ethernet is the name given to the use of the Ethernet protocol in an industrial environment, for automation and production machine control.

Until recently, a PLC (Programmable logic controller) would communicate with a slave machine using one of several possible open or proprietary protocols, such as Modbus, Sinec H1, Profibus, CANopen, DeviceNet or FOUNDATION Fieldbus. However, there is now increasing interest in the use of Ethernet as the link-layer protocol, with one of the above protocols as the application-layer (see OSI model).

Some of the advantages are:
* Increased speed, up from 9.6 kbit/s with RS-232 to 1 Gbit/s with IEEE 802 over Cat5e/Cat6 cables or optical fiber
* Increased overall performance
* Increased distance
* Ability to use standard access points, routers, switches, hubs, cables and optical fiber, which are immensely cheaper than the equivalent serial-port devices
* Ability to have more than two nodes on link, which was possible with RS-485 but not with RS-232
* Peer-to-peer architectures may replace master-slave ones
* Better interoperability

The difficulties of using industrial Ethernet are:
* Migrating existing systems to a new protocol (however many adapters are available)
* Real-time uses may suffer for protocols using TCP (but some use UDP and layer 2 protocols for this reason)
* Managing a whole TCP/IP stack is more complex than just receiving serial data
* The minimum Fast Ethernet frame size including inter-frame spacing is about 80 bytes, while typical industrial communication data sizes can be closer to 1-8 bytes. This often results in a data transmission efficiency of less than 5%, negating any advantages of the higher bitrate.
** On Gigabit Ethernet the minimum frame size is 512Bytes, reducing the typical efficiency to less than 1%.
** Some of the Industrial Ethernet protocols introduce modifications to the Ethernet protocol to improve efficiency.

Main protocols

"(Note the highly ambiguous name given the Ethernet version of DeviceNet. The "IP" in EtherNet/IP stands for Industrial Protocol.)"

References

*Arndt Lüder, Kai Lorentz (Editor), IAONA Handbook Industrial Ethernet, Industrial Automation Open Networking Alliance e.V., 150 S., Magdeburg (Germany), 2005, ISBN 3-00-016934-2, free copy at handbook(at)iaona.org.

External links

* http://www.industrial-ethernet.org
* [http://www.lammermann.eu/wb/pages/arbeiten/ethernet-as-a-real-time-technology.php Lammermann.eu: Ethernet as a Real-Time Technology]
* http://www.yr20.com - Expert Industrial Ethernet Problem Solving Professionals