Pepperl+Fuchs ES 58 EC Series Manual page 9

Absolute Rotary Encoders
Introduction
Ease of handling
EtherCAT is easy to use in comparison to classic fieldbus systems. Address assignment is
carried out automatically. Network tuning is not required. Built-in diagnostics with error
localization make the detection of errors very easy. Similarly, no switch configuration or
complex processing of MAC or IP addresses is needed as in the case of industrial Ethernet.
Functional principle and performance
EtherCAT's basic operating principle lies in the way that the participants (network node)
process the messages. The message sent from the EtherCAT master passes through each
participant. Generally, one message is sufficient to transmit the output information of the master
(e.g., SPS) to all participants and to import the input information to all participants with the
same message. Each network node reads the data intended for it from the message and adds
its data. This is done "on the fly", meaning that a message is practically only delayed by the
hardware lead times of a participant. This unique way to process the messages, makes
EtherCAT the fastest industrial Ethernet technology. No other technology can reduce
bandwidth usage or surpass the equivalent performance of EtherCAT. There is no need for
network switches and hubs.
Topology
An EtherCAT network can support up to 65,535 participants without restrictions in the network
topology. Line, Bus, tree, or star topology as well as combinations thereof are equally possible.
An additional Ethernet port in the master and an additional cable from the last participant to this
port extend the lines to a ring topology. With EtherCAT, cable redundancy is made possible
with simple measures. A software extension in the master stack is used for detection if
redundancy occurs.
Ease of handling
EtherCAT is easy to use in comparison to classic fieldbus systems. Address assignment is
carried out automatically. Network tuning is not required. Built-in diagnostics with error
localization make the detection of errors very easy. Similarly, no switch configuration or
complex processing of MAC or IP addresses is needed as in the case of industrial Ethernet.
Cabling and flexible connection/disconnection of participants
Due to the quick Ethernet physics, the distance between 2 participants can be up to 100 m
when using industrial Ethernet cable. Greater distances are possible with the use of fiber optic
cables.
For example, modular machines or tool changers require the option to connect or disconnect
individual participants or network segments during operation. For this, EtherCAT has additional
functions, which can achieve further topology flexibility, such as the exchange (hot swap) or the
connection (hot connect) of participants during operation.
Absolute rotary encoder and EtherCAT
The EtherCAT application layer communication protocol is based on the CANOpen
communication profile according to CiA DS-301 and is called "CANOpen over EtherCAT" or
shortened to "CoE." This protocol allows the use of the device profile DS 406 for the absolute
rotary encoder.
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