CANopen internal device structure
As illustrated, a CANopen device consists of three logical parts. The communication interface and protocol software handle the communication via the CAN network. The application software provides the internal control functionality as well as the interface to the process hardware interfaces. The CANopen object dictionary interfaces the protocol and the application software. It contains references for all used data types and stores all communication and application parameters.
The CANopen object dictionary
All communication and application objects belonging to a CANopen device are managed in a standardized listing - the CANopen object dictionary. In this object dictionary, each data that needs to be exchanged between the communication part and the application part of the device owns its unique 24-bit address. This address is divided in a 16-bit index and an 8-bit sub-index. Any entry in the CANopen object dictionary is readable via CANopen communication services. The default SDO channel of a CANopen device offers the system designer the possibility to configure the desired CANopen device behavior via the network.
Possibilities for the system designer
A system designer can configure and maintain a device via CANopen services due to the object dictionary definition. System designers can access the information where the device's setscrews are from the object dictionary. They can thus adjust the corresponding device behavior in the system. In the object dictionary range 1000h to 1FFFh they can adjust the desired communication behavior (e.g. participating a synchronous network behavior; establishing communication coherences between two or several network participants, etc.). In the object ranges 2000h to 5FFFh and 6000h to 9FFFh they can set the application specific parameters either in a manufacturer specific or standardized way.
