CANopen over Ethernet

Ethernet Powerlink is an industrial Ethernet network originating from the Austrian automation company B&R. The network was introduced in 2001 and standardized in 2003 by the Ethernet Powerlink Standardization Group (EPSG).

It is today an open network used in industrial automation plants all over the world, with a main concentration in the Central European market.

CANopen over Ethernet
In short, you could say that Powerlink is CANopen over Ethernet. This is simplifying matters a bit, but summarizes the main features of the network:

• The Ethernet standard — Powerlink keeps very close to the Ethernet standard, retaining original Ethernet features.
• The integration of CANopen technology — a robust and proven protocol widely used throughout the automation world.
• Special technologies developed by the EPSG such as the safety-oriented real-time protocol Powerlink Safety, or high-availability Powerlink networks with managing node redundancy.

The relation between Powerlink and CANopen. Put simply, POWERLINK replaces the transport medium CAN (left side) with Ethernet (right side). (Image source: http://www.ethernet-powerlink.org/)

What Powerlink does
Powerlink expands the Ethernet standard with a mixed polling and timeslicing mechanism. This enables:

• Guaranteed transfer of time-critical data in very short isochronic cycles with configurable response time.
• Time-synchronization of all nodes in the network with very high precision of sub-microseconds.
• Transmission of less time-critical data in a reserved asynchronous channel.

Modern implementations use cycle-times of under 400 µs (can reach as low as 200 µs) and a time-precision (jitter) of less than 1 µs.

Main features
One of Powerlink's key characteristics is that nodes on the network can communicate via cross-traffic, which works similar to the broadcast principle: all nodes on the network can receive data that any one sender among them supplies to the network. This way of communication does not require data to pass through the Master.

Powerlink supports all kinds of network topologies, star, tree, ring, or daisy chain, and any combination of them.

Hot plugging capabilities, easily accessible system diagnostics, and easy integration with CANopen are other features of Powerlink.

Powerlink works with the following standards:

• IEEE 802.3 Fast Ethernet
• IP-based protocols (UDP, TCP etc.)
• Standard device profiles: CANopen EN 50325-4 for automation
• Standard Ethernet chips.

POWERLINK FACTS
Network Type:	Scalable Ethernet-based advanced communication system
Topology:	Very flexible with line, bus, star or tree topology
Installation :	Hub based Ethernet transmission with shielded twisted pair cables and RJ45 connectors.
Data Rate :	100 Mbit/s
max. Stations:	240 including the Master
Data :	Each node: up to 1490 bytes per telegram frame Total: theoretically 1490x239
Network Features :	Combines the Ethernet standard with CANopen technology, plus special features developed by the ESPG.
User Organization:	Ethernet Powerlink Standardization Group (EPSG)

Sources:
http://www.ethernet-powerlink.org/
http://en.wikipedia.org/wiki/Ethernet_Powerlink