The SAE J1939 documents are intended for light, medium, and heavy-duty vehicles used on or off road, as well as appropriate stationary applications which use vehicle derived components (e.g., generator sets). Vehicles of interest include, but are not limited to, on- and off-highway trucks and their trailers, construction equipment, and agricultural equipment and implements.
The purpose of these documents is to provide an open interconnect system for electronic systems. It is the intention of these documents to allow Electronic Control Units to communicate with each other by providing a standard architecture.
This particular document, SAE J1939-21, describes the data link layer using the Classical Extended Frame Format (CEFF) with 29-bit IDs, as defined in ISO 11898-1, December 2015. For SAE J1939, no alternative data link layers are permitted.
This revision of the SAE J1939-21 Recommended Practice includes the following changes:
A final set of edits have been made to align this document with data frame format definitions that were updated in ISO 11898-1:2015
References to ISO documents used in this Recommended Practice have been corrected to identify the document and date of publication
Updated interframe timing for TP.BAM messages
Implementation rules for TP.CM_CTS and TP.CM_RTS messages have been updated, including guidance for error handling
Additional rules about responding to a Request message are included in the notes to Table 5
Binary numbering formats have been changed to include a subscripted letter b after the binary number (e.g., 010b)
Hexadecimal numbering formats have been changed to include a subscripted letter h after the hexadecimal number (e.g., FEh)
There have also been formatting changes designed to improve consistency (particularly with the use of abbreviations) and to correct errors in the text and in illustrations. Finally, some of the diagrams from the previous version of the document have been replaced with new diagrams, as the Drawing functionality that was available in Microsoft Word 2010 has been removed from Microsoft Word 2013, preventing changes from being made to the diagrams.
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