EtherCAT: How are SM0 & SM1 sync managers typically used?

In EtherCAT, the sync managers SM0 and SM1 are typically used for CoE (CANOpen over EtherCAT) mailbox communication. Essentially, mailbox communication is used for non-cyclic data exchange between the EtherCAT master and the slave devices.

• SM0 is typically used as MbxOut (Mailbox Output), that is, for Slave->Master communication
• SM1 is typically used as MbxIn (Mailbox Input), that is, for Master->Slave communication

For details you should check your EtherCAT slave’s ESI file (EEPROM specification) or the ESI XML file which can often be downloaded from the manufacturer’s website.

Source: Beckhoff website and ETG1000.6 V1.0.32, section 5.6.7.4.9 (requires free ETG membership).