4
Commissioning
28
Festo – P.BE-CPX-FB37-EN – 1406NH – English
4.3.3
Data access (data objects)
Asynchronous information can be exchanged with the EtherCAT devices via a mailbox mechanism.
Known data object models are used in part here, e. g. CoE (CAN over EtherCAT).
EtherCAT devices (I/O devices) have an object directory with all accessible objects.
An EtherCAT system can be configured by accessing the object directory of the individual participants.
The access mechanism is provided by Service Data Objects (SDOs).
There are two different communication mechanisms in an EtherCAT system.
The
Process Data Objects
(PDO) provide fast transfer of process data and are transmitted by simple
EtherCAT messages with no protocol overhead. Process Data Objects may be transmitted based on
event control, synchronised to a system clock, or on request.
The
Service Data Objects
(SDO) form a point-to-point connection and permit access to every entry in
the object directory of a node.
Access these data objects with the help of user programs created according to your specific require-
ments.
4.4
Addressing the devices
The higher-order controller is responsible for addressing the individual modules: The EtherCAT master
determines the position of the EtherCAT devices within the network.
The controller uses the following for local addressing:
–
The physical position of the device in the EtherCAT network (“Auto Increment Address”)
–
An independent EtherCAT device address (“EtherCAT Address”).
4.4.1
Assigning an independent EtherCAT device address via DIL switch
The bus node can be assigned an EtherCAT address using DIL switch 3 (
Section 3.2.9).
4.4.2
Assigning an independent EtherCAT device address using the configuration tool
The EtherCAT device address can be changed in the EEPROM using the configuration tool
(e.g. TwinCAT 3.x).
1. Remove the bus node from the EtherCAT network.
2. Write the new address into the EEPROM (
Fig. 4.1).
EtherCAT
Advanced Settings
ESC Access
Configured Station Alias
