CANopen over EtherCAT (CoE)

Question

1. CANopen is point to point communication while EtherCAT is bus based. Point to point means there will be node address. But this is redundant in EtherCAT. So I was wondering how this node address bytes are handled in the CANopen over EtherCAT. I tried searching for information but couldn't find anything specific on this.
   
2. Also, I assume both cyclic and acyclic data of the CANopen device is sent only cyclically over the EtherCAT because it is Master triggered cyclic transmission protocol. This basically means I cannot send asynchronous, event-triggered information at the trigger of the event, on EtherCAT (which is counter-intuitive for CAN's priority based because all of them get the same priority). Please correct me if I am wrong about this. Also please tell me how can I make a higher priority byte reach quicker than the lower priority one (assuming both occurred at the same time and assume there is bandwidth to send both at the start of new frame).

Answer 1

CANopen provides Process Data Object (PDO) and Service Data Object (SDO). PDO is sent cyclically over the EtherCAT and SDO is sent acyclically. Therefore, if you use the SDO, you send asynchronous, event-triggered information at the trigger of the event. Additionally, CANopen is usually used in the servo control and most of servo controller support the PDO and the SDO.