Synchronous serial transfer apparatus and synchronous serial transfer method

A synchronous serial transfer method for performing a synchronous serial transfer of data between a plurality of communication apparatuses through a communication line which is formed by one line,

• wherein said plurality of communication apparatuses each have a function of outputting a high impedance state to said communication line to replace a first potential and outputting a second potential as it is to said communication line, said second potential being complementary to said first potential, and
• a potential fixing apparatus is connected to said communication line, said potential fixing apparatus fixing a potential on said communication line to said first potential when all outputs of said plurality of communication apparatuses are in a high impedance state,
• said method comprising the steps of:
• (a) outputting a clock signal in which said second potential and said high impedance state is periodically given, from a receiving end communication apparatus which is to receive said data out of said plurality of communication apparatuses;
• (b) outputting said data as they as superimposed over said clock signal, from a transmission end communication apparatus which is to transmit said data out of said plurality of communication apparatuses so that said potential fixing apparatus creates transmission data which are formed by said first and said potentials;
• and
• (c) detecting by said transmission end communication apparatus whether said transmission data have said first potential or said second potential, at timing of a rise or a fall of said clock signal.