Fig.164: Diagram showing a CoE write access with operation via AoE ADS
The EL6695 has a CoE directory on both sides, whereby at least one side is declared user-specific. As a rule, in this mode the EL6695 does not establish connections between CoE A and CoE B. The two controllers are therefore not able to exchange parameters acyclically via CoE, and write access on one side cannot inform the master on the other side. Therefore, the following data exchange mechanism is implemented in the EL6695 via Beckhoff ADS:
Assumption: at least one side is a TwinCAT system or a EtherCAT master, which supports Beckhoff AoE (ADS over EtherCAT). In this example master B is such a system, master A only supports CoE.
A write/read access by master A to CoE A is transferred to CoE B.
The EL6695 reads the target Ams-NetID from CoE B 0xF820 and sends an AoE ADS write/read indication to the specified address, where a service has to pick up and process this indication. In the TwinCAT PLC this may be an FB ADSWRITEIND/ADSREADIND from the TcSystem.lib, for example.
From the PLC then use ADSWRITERES/ADSREADRES to send the response back to the EL6695. Use the own AMS Net ID as target address from CoE A 0xF821. During startup the EtherCAT master should load this into the EL6695 as AoE Init Cmd.
The EL6695 can now return the CoE write/read response to master A
The transfer time should be taken into account for this process.
This AoE mechanism operates in the CoE areas where AMS NetIDs are stored.
Fig.165: Adoption of the NetID
NOTICE
Mode “partial object directory”:
Parts of the OD are downloaded and inserted into the OD.
Mode “partial object directory with mirrored objects”:
Parts of the OD are loaded into the EL6695 and inserted into the OD. In addition, mirrored objects are created in the remote OD. This mode enables a direct data link between CoE A and CoE B, without the AoE mechanism referred to above. However, this mode only covers the parameter range 0x8nnn:
CoE A 0x8000 – 0x87FF is mirrored to CoE B 0x8800 – 0x8FFF
CoE B 0x8000 – 0x87FF is mirrored to CoE A 0x8800 – 0x8FFF
The 0x88xy objects are therefore “Read Only” (RO)
NOTICE
The mode “complete”, “partial”, “mirrored” is set via the content of the *.coe file in the EL6695
Fig.164: Diagram showing a CoE write access with operation via AoE ADS
Fig.165: Adoption of the NetID