Within an electrophotographic copying machine having a predetermined number of sensing elements each deriving an output indicative of respective one of operating states of the machine, there is provided a single chip, MOS-LSI microprocessor responsive to the outputs of the sensing elements to control the machine in a sequential or serial mode. The microprocessor contains storage means storing a string of instructions, processing means to fetch sequentially the instructions from the storage means and to deal with the fetched instructions, first input means to receive synchronizing signals generated within the body of the machine, first output means to determine with aid of the processing means whether any synchronizing signal is inputted via the first input means and to produce confirmation signals after confirming the sensed operating states of the machine, second input means to introduce through the sensing elements the confirmation signals supplied via the first output means, and a second output means to process with aid of the processing means the signals received by the first input means and the second input means and to consequently produce control signals effective to control operation of the machine.