An object of the present invention is to provide a data communication technique which can reduce a size of a system by enabling bidirectional data communication, and enables a cheap system configuration. A data communication apparatus is provided, the data communication apparatus including a signal terminal (IN) for inputting receiving signals of pulses of which rise times or fall times are mutually different, a reference voltage terminal (GND) for inputting a reference voltage, a rise detection circuit (11) for detecting a rise or a rise time of the receiving signal, a fall detection circuit (12) for detecting a fall or a fall time of the receiving signal, a data signal conversion circuit (13) for generating a clock signal or a data signal based on a result of a detection by the rise detection circuit or the fall detection circuit, and an internal circuit (14) for inputting the clock signal or the data signal generated by the data signal conversion circuit, and for outputting a transmission signal to the signal terminal.