The CAN application layer CANopen consists of the communication profiles and the device profiles which standardize the data content for the corresponding device classes. The communication profiles control the mode of data exchange between the devices. Thereby a difference is made between real-time data (Process Data Objects) and parameter data (Service Data Objects). CANopen defines different communication modes for the transmission of the PDOs:
Process-controlled: The telegrams are only transmitted in the event of state change. Only the actual change is transmitted and not the complete process image.
Cyclic / synchronous: The SYNC induces the modules to take over the output data and to transmit new input data.
Request: The CAN data request telegram induces the modules to send their input data.