An image processing system having operating and stand-by modes of operation which are to be selectively put into effect, including a plurality of slave data processors each operative to execute a set of predetermined functions assigned thereto, a master data processor for controlling the operation of each data processor, the master data processor being operative to output a data processing command requesting any of the slave data processors to execute any of the predetermined functions assigned to the slave data processor and a control command predominant over the communication of data dictating the operation of each slave data processor, and an interface bus providing connection between the master data processor and each slave data processor for allowing transmission therethrough of the data processing command and the control command to any of the slave data processors, the master data processor being operative to detect a state in which the master data processor is currently coupled to any one of the slave data processors through the interface bus to allow transmission of the data processing command or the communication control command to the particular one of the slave data processor, wherein, in an operating mode of operation of the system, the data processing command or the control command is distributed through the interface bus exclusively to the particular slave data processor which is detected to be currently coupled to the master data processor.