SERIAL TRANSMISSION SYSTEM

PURPOSE:To improve the freedom and operation efficiency of a system by providing a master function or a slave function to an optional circuit as required without fixing a master circuit and a slave circuit. CONSTITUTION:Transfer circuits Ca-C4 have terminals T1 and T2 respectively and the terminals T1 and T2 are connected mutually. The terminals T1, T2 have respectively switches SW1, SW2 connecting the terminals T1, T2 respectively to registers RG1, RG2. The RG1 is a register strong a data to be transmitted with parallel input/serial output system, and the RG2 is a register storing a received data with serial input/parallel output system. The RG1, RG2 are connected to a computer CON via a bus line BUS. The switches SW1, SW2 decide that which terminal of the terminals T1, T2 is to be connected to the registers RG1, RG2 depending on the content of the register RG3.