COMMUNICATION PROTOCOLS (CONT’D) Communication Methods •
Single frame message : data length =< 8bytes
•
Multi-packet Broadcast message : data length > 8bytes (Multi-packet RTS/CTS session is under development.)
•
Multi-packet Broadcast message is used to send DTCs (Diagnostic Trouble Code) and component ID etc.
The table below indicates which service item is required which set of Request/Response procedure.
No.
Item
1
J1939-71 Application Layer Send/ Receive Message Active Diagnostic Trouble Code
2 3
4
Previously Active Diagnostic Trouble Code
Diagnostic Data Clear/Reset of Previously Active DTCs
Description Single frame message Multi-packet message Global Destination On request Global, Multipacket message Global Destination On request Specific, Multipacket message Destination Specific On request, Acknowledgement On request Specific, Acknowledgement
Data length
Request PGN 59904
Response
TP Used
≤8bytes
None
DA Global
NA
>8bytes
None
DA Global
BAM
DA Global
DA Global
BAM
DA Specific
DA Specific
RTS/ CTS
DA Global
DA Global
NA
DA Specific
DA Global
NA
>8bytes
≤8bytes
*.TP=Transport Protocol , BAM=Broadcast Announce Message
NOTE: Specific destination request session is under development. Notes to the table above-General rules of operation for determining whether to send a PGN to a global or specific destination: --- 5.4.2 J1939-21 •
If the Request is sent to a global address, then the response is sent to a global address.
NOTE: A NACK is not permitted as a response to a global request. •
If the Request is sent to a specific address, then the response is sent to a specific address.
NOTE: A NACK is required if the PGN is not supported. If the data length is more than 8 bytes, the Transport Protocol RTS/CTS must be used for the response to a specific address. •
Exceptions: PDU2 format PGNs with 8 bytes or less can only be sent to a global destination because there is no destination address field in the PDU2 Format. The Address Claim PGN is sent to the global destination address even though the request for it may have been to a specific destination address (see J1939-81).(N/A) The Acknowledgment PGN response uses a global destination address even though the PGN that causes Acknowledgment was sent to a specific destination address.
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E55W, E60, E80 Electronic Control System Manual
