Fragmented Message

The properties of a parameter group and how they differ from a “pure” CAN message are described in chapter General Information on the Parameter Group. It is mentioned there that the data length of a PGN is not limited to 8 bytes. However, because CAN is used as a physical transport layer, a data packet with more than 8 bytes must be divided by the sender into individual packets, which can then be sent with a CAN message each. The receiver must recombine the individual fragments in their original order. A set of rules is defined for this in the J1939 standard: a so-called transport protocol.