- 1. Introduction
- 2. General Description of the Protocol
- 3. Document Structure
- 4.1. Names and Addresses
- Device Names
- 4.2. Parameter Group
- Structure and Type of a Parameter Group
- Example of a Global Parameter Group
- Example of a Specific Parameter Group
- Parameter Groups reserved specially for the Protocol
- 4.3. Data Management
- Suspect Parameter Number (SPN)
- SLOT Definition
- 5. Network Management
- 6. Transport Protocols (Multi-packet Messages)
- 7. Diagnostics
The CAN protocol describes the addressing type of the message addressing. This means that all information is marked by an identifier and can be interpreted and evaluated in this way. In addition to the message addressing, there is also node addressing implemented as software in J1939. This makes point-to-point communication possible. Each bus node in a J1939 network gets a node address for this.
Important: Each ECU that sends in a J1939 network requires a valid address. The node address consists of an 8-bit value and can be permanently assigned to the node once (static network). However, networks can also be defined in which the nodes search for their addresses independently (dynamic network). Which of the two network types is used depends on the respective application.
If the J1939 protocol is being used in the classic sense in the drive train of a truck, a static network is usually found in which the network topology and the addresses have already been specified when the vehicle was completed. In such a network, the address assignment and the topology remain constant over the entire life cycle of the vehicle.
In dynamic networks, the topology of the networks can change during runtime. Known as well as unknown network nodes may be added. It is even possible for multiple ECUs of the same type to be present in a network. A typical application for a dynamic network is the ISO 11783 protocol that is used in agricultural engineering and describes the communication between a tractor and its add-on equipment (implement).