A downlink communication data DND from a main control circuit section to a combination control circuit section is divided into first and second downlink data, high-speed communication using a downlink clock signal and a transmission start instruction signal is performed, a high-speed load which has been directly driven from the main control circuit section is indirectly driven at high speed from the combination control circuit section by the first downlink data, a low-speed analog input signal ANL which has been indirectly inputted to the combination control circuit section is inputted to a specific input channel of a multi-channel converter through an indirect multiplexer, and channel selection is made by the downlink communication data.