The ITS bus is intended for use as a secondary bus to allow communications between the electronic modules which control the vehicle and aftermarket mobile office components such as GPS, cell phones, and pagers. A gateway, designed into the vehicle, would control which messages arrive on the automotive main bus. For communications within an electronic module, an SPI Interface is commonly used. It consists of four wires, Clock, Data In, Data Out, and Chip Select, and has a master device connected to slave devices. A typical implementation consists of a master microprocessor, and slave IC's such as power output drivers and memory.
Serial data is a very important part of a vehicle's electrical architecture.
A direct result of a communication bus in a vehicle is saved wiring, but the indirect results are even more important. With the number of wires reduced, the vehicles weigh less, and the ultimate result is increased gas mileage. Also, with a bus in place to share information between modules, the need for redundant sensors is eliminated, and overall vehicle cost is reduced.