J1939

The SAE J1939 protocol is a protocol specified by the American Society of Automotive Engineers (SAE) with which electronic components of commercial and special vehicles communicate with each other. J1939 is used in the J1939 bus, which is a field bus based on the CAN bus.

The protocol stack of the SAE J1939 protocol is based on the OSI reference model and functionally takes into account the application layer, network layer, linklayer and physical bit transmission layer. This means that the J1939 bus has bridging and routing functions and the SAE-J nodes have their own addresses. This was made possible by the extended format of the identifier in the CAN data frame, which in this format comprises 29 bits. 8 bits of the identifier field are used as address bits for the source and destination addresses of the SAE-J nodes. This allows J1939 to support a total of 254 logical nodes and 30 physical ECUs per segment. The information is described as signals and combined in parameter groups.

The SAE J1939 protocol, which is used in commercial and rail vehicles, agricultural machinery and ships, takes into account segmentation, flow control, the type of transmission, which can be acknowledged or unacknowledged, and also specifies the message content.