a and b also execute the data dataa and datab that has been held this control will become apparent from the explanation of fig8 described later in fig5 if the station a and a do not have a data hold function the data dataa and datab is executed successively fig6 shows a system block diagram as one embodiment of a vtr that applies the serial communications system of this invention a microcomputer 100 which controls the system according to the program generates as necessary clock data address and tail mark that were described by referring to fig1 to 5 and works as a sending station that outputs them to receiving stations one example method of generating the tail mark using the microcomputer 100 will be explained in detail by referring to fig7 a bus 120 includes one clock line that carries the transfer clock sc and one data line that carries the serial data sd semiconductor integrated circuit devices 102 104 106 108 110 are electrically connected through the bus 120 to the microcomputer 100 and constitute receiving stations that receive the clock data address and tail mark output from the microcomputer 100 through the bus 120 the device 102.