ABSTRACT
Ethernet Powerlink (EPL) is a real-time open protocol that uses both mixed polling and time slice mechanism for deterministic data transmission. Data which is less time critical in nature can be sent in asynchronous mode. For this purpose, a gateway is used. The protocol enables integration of different networks—i.e., it is an industrial Ethernet solution designed to give users a single and integrated means for handling all communication tasks in today’s automation systems. Hubs, and not switches, are used to limit EPL jitters. It has a cycle time around 200 µs and jitter below 1 µs and is particularly suitable in multi-axis drive applications. EPL supports “on the fly,” i.e., hot plugging is possible. It supports both client/server and producer/consumer communications.
Operation is based on a managing node (MN) speaking to the other nodes (called controlled node (CN)) one after the other cyclically on a precise time schedule basis. MN defines the clock pulse for synchronization of all devices and manages the data communication cycle in the network.
Multiplexing is used in EPL such that critical data can be sent in every cycle while less critical data can be sent intermittently.
EPL is a “any topology” network—i.e., it may have tree, star, ring, daisy chain, or a combination of them. It has redundancy and safety features also.
