Parameterization and commissioning
EL6751
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Version: 3.5
CAN bus parameters
The CANopen configuration is carried out via SDO download in the PREOP state. The objects to be loaded
must be transmitted either with Complete Access or with consistency nesting (first set SubIndex 0 to 0, then
write SubIndex 1-n, then set SubIndex 0 to n). Care should thereby be taken to always start with object
0xF800. After receiving the object 0xF800, the EL6751 switches the CAN controller with the appropriate
baud rate from 0xF800:02 to ONLINE.
CANopen slave configuration
After object 0xF800, the objects 0x8yy0, 0x8yy6 (if the CANopen slave has CAN TxPDOs), 0x8yy8 (if the
CANopen slave has CAN RxPDOs) and 0x8yy3 (if application-specific StartUp-SDOs are to be sent to the
CANopen slave before the sending of the CAN Start Node command) must be transmitted in this order for
each CANopen slave to be configured. yy is to be incremented (starting from 0) for each CANopen slave to
be configured.
PDO Mapping
For each configured CANopen slave, there is an EtherCAT RxPDO (if the CANopen slave has CAN
RxPDOs) and an EtherCAT TxPDO (if the CANopen slave has CAN TxPDOs). The PDO mapping of the
EtherCAT PDOs is automatically calculated by the EL6751 after the download of the respective 0x8yyz
objects and can be read. The PDO mapping objects 0x16yy and 0x1Ayy thereby belong to the configuration
objects 0x8yyz. The PDO mapping objects can only be written with the values that the EL6751 has
calculated itself. The writing of the PDO mapping thus serves only to check the PDO mapping calculated by
the EtherCAT configurator and can therefore be omitted.
PDO Assign
In addition, there are a few other EtherCAT PDOs that contain control, status and diagnostic information.
These PDOs are selected via the PDO Assign. It should thereby be ensured that all EtherCAT PDOs that are
assigned to the configured CANopen slaves (PDO number <= 128) always appear in the PDO Assign. With
regard to the order of the PDOs in the PDO Assign, it is important to ensure that the index of the assigned
EtherCAT PDO increases with each entry in the corresponding PDO Assign object. If the EtherCAT master
does not transmit any PDO Assign in the StartUp SDOs, then PDOs 0x1A83 and 0x1A85 are assigned for
status and diagnosis.
Cyclic CANopen communication
During the transition to SAFEOP, the EL6751 checks the length configured in the Sync Manager channels 2
and 3 against the length calculated from PDO Mapping and PDO Assign. The SAFEOP state is only adopted
if these lengths match. In the SAFEOP state, the EL6751 starts the boot-up of the configured CANopen
slaves. After the transmission of all CAN StartUp SDOs, the respective CANopen slave is started with the
‘Start Node’ message and the CAN PDO communication is active. All outputs in the CAN RxPDOs are
thereby set to 0. As soon as the EL6751 has been switched to OP, the data from the EtherCAT outputs are
also adopted into the CAN RxPDOs.
Configuration of the EL6751 by scanning the CAN bus
The following flow chart shows the sequence of the configuration of the EL6751 by scanning the CAN bus:
