SAE J1939 Arbitration ID
J1939 is a high-speed, Class C type communications network designed to support real-time closed loop control functions between electronic control devices, which may be physically distributed throughout the vehicle.
The J1939 protocol typically uses the 29-bit or the extended format for the arbitration IDs. As shown in the following figure, the arbitration ID comprises of the Priority (first 3 bits), Parameter Group Number (PGN) (18 bits), and the Source Address (8 bits).
29 Bit Arbitration ID
Most messages on J1939 are intended to be broadcast. This means the data is transmitted on the network without directing it to a specific destination. This permits any device to use the data without requiring additional request messages. However, by modifying the PGN, you can direct messages to a specific address (destination address). As shown in the following figure, the PGN comprises of a reserved bit (first bit), data page (1 bit field), PDU (Protocol Data Unit) format (8 bit fields), and the PDU specific field (8 bit fields). PDU specific fields can either represent a group extension or a specific destination address depending on the value of the PDU format fields. For example, for PDU formats between 240 and 255, the PDU specific field denotes a group extension. For PDU formats less than 240, the PDU specific field denotes a destination address.
Parameter Group Number
For a detailed description of the J1939 terminology, refer to the SAE J1939 specifications.