A single parallel bus interconnects the various portions of a central processing unit. Data transmission between the various portions of the processor is based on sequential use of the common bus, and is synchronized by control circuitry. Circuit means are included for providing access of the various portions of the processor to the bus, and includes means for generating data on the bus for transmission, and for detecting data transmitted by the bus. To minimize access time to the bus whenever data is to be transmitted, means are provided for precharging the bus to a reference potential and then selectively discharging the bus to correspond to the data to be transmitted. In a different aspect of the invention a common bus is used to transmit data between the processor and computing equipment separate from the processor. In this aspect of the invention, circuitry is provided for detecting current on the bus corresponding to data, and for amplifying this current to a suitable level, and then generating a voltage suitable for transmission by the bus.