Universal SDO: Uni-, broad-, and multi-cast

One of the most important features of the CiA 1301 CANopen FD application layer is the USDO service allowing with one CAN-ID to communicate with all other nodes.

The USDO (universal service data object) protocol benefits from the larger payload of the CAN FD frames. It uses some of these bytes for protocol information. The CAN-ID contains the node-ID (7 bit), which is the source address, and the service type (4 bit). One byte in the USDO protocol information provides the destination address indicating the node-ID of the receiver (unicast), or the user-specified group of receivers (multi-cast), or that all nodes are addresses (broadcast).

The USDO service saves the CAN-ID resource (2048 for the base frame format). In opposite to the SDO service, the USDO allows to communicate with all nodes without configuring additional channels or using of an SDO manager. CANopen FD users can switch-on the network and the confirmed USDO channels are already established. This simplifies system integration dramatically. The increased throughput could allow in some applications just to use USDO services to communicate process data. This would even avoid to configure PDOs.

Learn more about CANopen FD on this website or visit one of CiA’s CANopen FD seminars.