method in which an instance number is assigned to each physical unit of a certain type. An idea that underlies much of RV-C's design is that "every data packet stands alone". That is, with very few exceptions, all the information necessary to interpret a data packet is contained within that packet. This greatly reduces the memory and speed required for a microprocessor to implement the protocol. In general, the committee has been intent on keeping the cost of implementation to a minimum. Relationship to SAE J1939 RV-C draws heavily from the SAE J1939 protocol. The primary differences between J1939 and RV-C are: SAE J1939 does not support RV-C's "instancing". The main diagnostic message (DM1) has somewhat different formats, due to the need in RV-C for instance identification. The SAE J1939 NAME PGN is simplified in RV-C. Links The RVIA web site for RV-C Automotive electronics