The relationship between SAE-J1939 and CAN2.0B

SAE J1939 (hereinafter referred to as J1939) is the recommended standard of the American Society of Automotive Engineers (SAE). digital communication between electronic components.The relationship between SAE-J1939 and CAN2.0: CAN2.0 is a bus specification and a technology of the data link layer. J1939 is a specification defined by SAE (American Automobile Association) based on CAN bus, which is mainly used to solve rs485 ethernet adapter the compatibility problem between different engine manufacturers and different ECU manufacturers. J1939 defines a series of PGNs and SPNs, these PGNs contain the information of various parts of the car such as engines, transmissions, axles, etc.; the representation method (state and value) of parameters also defines SLOT (Scaling-proportion, Limit-limit, Offset—offset, Transfer—transmission). ECU manufacturers should follow this specification when developing equipment. ECU modules have different functions and different manufacturers. On the basis of J1939, they show their diversity: support or not support some PGNs, SPNs and SLOTs; add some PGNs and SPNs that are not defined by J1939.SAE-J1939 and CAN2.0B message frame format: The CAN2.0 specification includes CAN2.0A (standard frame format), CAN2.0B (extended frame format), and the two use different frame format bit codes. J1939 is further encapsulated on the basis of CAN2.0B, RS485 to TCP/IP converter and redefines the 29-bit ID of the arbitration field part. Only standardized communications are defined for the extended frame format in SAE-J1939, therefore, SAE-1939 devices must use the extended frame format. SAE-J1939 integrates each data frame (PDU, protocol data unit) into a CAN2.0 data frame