Beckhoff EL6731 Documentation page 136

EtherCAT communication EL6731-00x0
DP bus parameters
The DP 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
[} 158]. After the receipt of object 0xF800, the EL6731 is active on the PROFIBUS with the corresponding
baud rate from 0xF800:02 (FDL only, no DP).
DP slave configuration
After object 0xF800, the objects 0x8yy0 [} 154], 0x8yy1 [} 155] and 0x8yy2 [} 155] must be transferred in this
order, depending on the DP slave to be configured. yy is to be incremented (starting from 0) for each DP
slave to be configured.
PDO Mapping
For each configured DP slave there is an EtherCAT RxPDO (if the DP slave has DP outputs) and an
EtherCAT TxPDO (if the DP slave has DP inputs). The PDO mapping of the EtherCAT PDOs is automatically
calculated by the EL6731 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 EL6731 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 DP slaves (PDO number <= 125) 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 the PDOs 0x1A81 [} 146], 0x1A82 [} 147],
0x1A83 [} 147], 0x1A84 [} 147] and 0x1A85 [} 147] are assigned for status and diagnosis.
Cyclic DP communication
During the transition to SAFEOP, the EL6731 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. The EL6731 starts communication with the configured DP slaves in the SAFEOP
state. Fail Safe data are sent to the DP slaves as long as the EL6731 is in SAFEOP. As soon as the EL6731
has been switched to OP, the data from the EtherCAT outputs are transmitted to the DP slaves.
Configuration of the EL6731 with Backup Parameter Storage
The following flow chart shows the sequence of the configuration of the EL6731 with Backup Parameter
Storage:
136 Version: 2.8 EL6731