State machine

Configuration of the EL6731 with StartUp SDOs:

The following flow chart shows the sequence of the configuration of the EL6731 with StartUp SDOs:

Following a power-on, the EL6731 is in the INIT state and has no DP configuration.  The EL6731 is not active on the PROFIBUS.

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. 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, 0x8yy1 and 0x8yy2 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, 0x1A82, 0x1A83, 0x1A84  and 0x1A85 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:

Following a power-on, the EL6731 is in the INIT state and has no DP configuration. The EL6731 is not active on the PROFIBUS.

DP bus parameters / DP slave configuration

The configuration stored in the Backup Parameter Storage object 0x10F2 is loaded during the transition from INIT to PREOP. Since the StartUp SDOs from the Configuration of the EL6731 with StartUp SDOs are stored in the Backup Parameter Storage object, the sequence is the same as the one described there. Hence, the stored data is initially written to object 0xF800 and the EL6731 is active on the PROFIBUS with the corresponding baud rate from 0xF800:02. Subsequently, the DP slaves are generated according to the stored DP slave configuration. If the PREOP state is quit, the current DP configuration in objects 0xF800, 0x8yy0, 0x8yy1 and 0x8yy2 can be read. The cycle time of the EtherCAT master (0x1C32:02) must still be transmitted before the EL6731 is switched to SAFEOP.

PDO Mapping / PDO Assign

In addition, the EtherCAT master can also read the PDO Mapping and PDO Assign in the PREOP state in order to determine the lengths of the EtherCAT process data.

Creating the Backup Parameter Storage

The Backup Parameter Storage can be created as follows:

1. Download object 0x10F2 (in PREOP without having sent StartUp SDOs beforehand): in this case the data received will be saved as Backup Parameter Storage in the flash memory

Deleting the Backup Parameter Storage

In order to load a new Backup Parameter Storage or to simply delete the existing one, the value 0x64616F6C has to be written to entry 0x1011:01.