Abstract: In a data processing system comprising at least two microcomputers, one microcomputer (1) serves as a master to control the or each other microcomputer (2, 3 respectively) as a slave. In order to improve that utilization of the system the bus (4) of the master serves as a common bus and each slave has associated with it a buffer memory (5, 6 respectively) for the intermediate storage and transmission of data. The buffer memory can be connected, by means of an associated switching device (7, 8 respectively), alternately to the bus (9, 10, respectively) of the slave and to the common bus thereby switching the address field constituted by the buffer memory into the address space of the slave and into the address space of the master respectively. Furthermore, each slave has associated with it two interconnected input/output interfaces (11, 12 and 13, 14 respectively which serve for transmission of status signals concerning the master of the relevant slave.