Dbc File Format Documentation

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without going into a huge discussion on can, can frames are a bit of a special case in how they are handled by can networks. there are usually two types of can frame formats, which are defined in j1939 dbc, j21 can, and a2b1. the standard message formats are:


 standard message format - this message is a master frame of the can network. it identifies the can message in the data field, defines the value of the sae j1939 ids, and defines which of the other standard identifiers are included in the message. 


 extended message format - this message is a master frame of the can network. it identifies the can message in the data field, defines the value of the sae j1939 ids, and defines which of the other standard identifiers are included in the message. it also defines additional data that is not included in a standard can message. 


the standard message format is identified by the class 1, data type 0xf1 in the data field. this is the modified message format. the standard message format defines a standard set of ids, including sae j1939 and sae j21 ids, and the standard message format includes e.g. a message number, node id, the can id, and direction of the message (transmit or receive). 


the extended message format is identified by the class 1, data type 0xf2 in the data field. this is the extended message format. the extended message format includes a different set of ids, including sae j1939 and sae j21 ids, and in addition, the extended message format defines many more identifiers, including a can id, an error and warning code, a message type, and on top of that, allows for the inclusion of the can id extension which is used to add additional identifiers and parameter information to the can message. it is worth noting that this can id extension is not mandatory, and a can network can implement the standard message format without it, but most are likely to implement the extended message format with the can id extension. 84d34552a1