MESSAGE FORMAT (CONT’D) J1939-21 Data Link Layer (See Appendix B) Acknowledgment Definition: The Acknowledgment PG is used to provide a handshake mechanism between transmitting and receiving devices. Transmission repetition rate: Upon reception of a Parameter Group Number that requires this form of acknowledgment. Data length: 8 bytes Data Page: 0 PDU Format: 232 PDU Specific: Destination address1 = Global (255) Default priority: 6 Parameter Group Number: 59392 (0x00E800) Data ranges for parameters used by this Message Type: Control byte: 0 to 3 See definitions below 4 to 255 Reserved for assignment by SAE Group Function Value 0-250 Definition is specific to the individual PGN, when applicable. Most often it is located as the first byte in the data field of the applicable Group Function PG. 251-255 Follows conventions defined in J1939-71 Positive Acknowledgment: Control byte = 0 Byte: 1 Control byte = 0, Positive Acknowledgment (ACK) 2 Group Function Value (If applicable) <N/A> 0xFF 3-5 Reserved for assignment by SAE, these bytes should be filled with 0xFF 6 Parameter Group Number of requested information (8 LSB of parameter group number, bit 8 most significant) 7 Parameter Group Number of requested information (2nd byte of parameter group number, bit 8 most significant) 8 Parameter Group Number of requested information (8 MSBs of parameter group number, bit 8 most significant) Negative Acknowledgment: Control byte = 1 Byte: 1 Control byte = 1, Negative Acknowledgment (NACK) 2 Group Function Value (if applicable) <N/A>0xFF 3-5 Reserved for assignment by SAE, these bytes should be filled with 0xFF 6-8 Parameter Group Number of requested information (see above) Access Denied: Control byte = 2 Byte: 1 Control byte = 2, Access Denied (PGN supported but security denied access) 2 Group Function Value (if applicable) <N/A>0xFF 3-5 Reserved for assignment by SAE, these bytes should be filled with 0xFF 6-8 Parameter Group Number of requested information (see above) Cannot Respond: Control byte = 3 Byte: 1 Control byte = 3, Cannot Respond (PGN supported but ECU is busy and cannot respond now. Re-request the data at a later time.) 2 Group Function Value (if applicable) <N/A> 0xFF 3-5 Reserved for assignment by SAE, these bytes should be filled with 0xFF 6-8 Parameter Group Number of requested information (see above) Request Definition: Used to request a Parameter Group from a network device or devices. Transmission repetition rate: Per user requirements, generally recommended that requests occur no more than 2 or 3 times per second. Data length: 3 bytes (The CAN frame for this PG shall set the DLC to 3.) Data page: 0 PDU Format: 234 PDU specific field: Destination Address (global or specific) Default priority: 6 Parameter Group Number: 59904 (0x00EA00) Byte: 1,2,3 Parameter Group Number being requested 20-30-7 143 of 182
E55W, E60, E80 Electronic Control System Manual
