The bidirectional one-wire bus is one of the first ways to access to control devices. The entire communication runs over only one wire and is used for data transmission according to ISO 9141 in the automotive industry. The bus serially receives and sends data via one data line each. The data is transmitted using half-duplex technology.
This means that the sending and receiving of messages does not happen at the same time, since both terminals operate on the same channel. If an L-line is used in addition to the K-line, data communication can also take place unidirectionally, i. e. only in one direction. In the meantime, the K-Line is frequently replaced by a CAN bus, as it is considered to be more efficient and effective in terms of the exhaust emission standard.
One application example is the on-board diagnosis of control units. The K-Line was already integrated as a standard in the first OBD standard and has been supported ever since. The communication between the control unit and the diagnostic module is initialized using what is known as stimulation. There are two types of fast initialization and 5-baud initialization.