coldlkp.blogg.se

The structure of a PGN permits a total of up to 8672 different parameter groups to be defined per page. Each PG (a grouping of specific parameters) has a definition that includes the assignment of each parameter within the 8-byte data field (size in bytes, location of LSB), and the transmission rate and priority of the message.

The PGN uniquely identifies the Parameter Group (PG) that is being transmitted in the message. This type of message, one that is sent to all ECUs on the bus, is called a PDU2 message. The GE provides a larger set of values to identify messages that are broadcasted to all nodes on the network. If the PF field is between 240 and 255, then the PS field will contain a Group Extension (GE). This type of message, one that can be directed to a specific ECU on the bus by sending the message to its address, is called a PDU1 message. If the Global Address (FF16) is used, then all nodes on the bus will receive the message. If the PF value is between 0 and 239, the PS field will contain the destination address of the node that will receive the message. The PS is dependent on the value in the PF field. The PF and PS are both a byte (8-bits) long. PDU stands for Protocol Data Unit, and can also be read as the message format. The PGN is a combination of the Reserved bit (always 0), the data page bit (currently only 0, 1 is reserved for future use), the PDU Format (PF) and PDU Specific (PS).

What is a PGN? A Parameter Group Number (PGN) is a part of the 29-bit identifier sent with every message.

Every message includes a 29-bit identifier, which defines the message priority, what data is contained within the 8-byte data array that follows the identifier, and which ECU sent the message. What kinds of messages are sent on a J1939 network? Any electronic control unit (ECU) using J1939 is permitted to transmit a message on the network when the bus is idle. The J1939 network is a specific communication system, supporting specific sets of applications and a specific industry, rather than being generalized. It is a high-level protocol that defines how communication between nodes (modules) occurs on the bus. What is SAE J1939? The Society of Automotive Engineers (SAE) developed the J1939 standard to be the preferred CAN for equipment used in industries ranging from agriculture, construction, and fire/rescue to forestry, materials handling as well as on and off-highway vehicles.