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Police cars, taxi/cabs, and other special-purpose passenger cars are equipped with add-on devices such as blue-light, special horns, taximeter, digital radio, etc. In the past, such equipment was connected via discrete I/O lines or proprietary interfaces, e.g. RS-232, RS-485, J1850, or CAN. The CAN in Automation (CiA) international users and manufacturers group has established a technical group specifying an open CAN-based network for such car add-on devices. The physical layer is based on ISO 11898-2 (CAN high-speed), and the CAN data link layer (ISO 11898-1) uses the base frame format (11-bit CAN identifier). The selected application layer is compliant to CANopen (EN 50325-4). In order to achieve easy system integration, the group is specifying an application profile describing the content of the transmitted messages.

Several companies have implemented in silicon the international standardized Controller Area Network (ISO 11898). The layered data link layer provides basic communication services such as transmission of data and requesting of data. The CAN protocol also handles the detection of failures as well as the error indication. All existing implementations use the same protocol handler, which has to be compliant with the C or VHDL reference model from Bosch. The implementations differ in the acceptance filtering, the frame storage capabilities, and in additional, nice-to-have features.