In a serial interface system wherein a master unit (26, 27) selects one or more of slave units (26, 27) as a destination by an identification number assigned to each slave unit and transmits a data signal to the destination in synchronism with a clock signal, a control path is added to a serial interface....http://www.google.com/patents/US4872003?utm_source=gb-gplus-sharePatent US4872003 - Serial interface system flexibly applicable to a one-to-plurality connection
