PURPOSE: To eliminate the need to pay attention to circuit control in accessing data and to perform data processing speedily in a small number of program steps by connecting the output signal of a control circuit information circuit directly to various address buses.

CONSTITUTION: Information requested by plural terminal devices 3 through a circuit controller 2 is processed by a central processing unit (CPU) 1. The circuit controller 2 controls a terminal circuit to transfer information from the terminal devices 3 to the CPU1 and information from the CPU1 to a corresponding terminal circuit. The circuit controller 2 monitors the arrival of commands from the CPU1 and data access requests from the terminal devices 3 in command execution normally, but when there is no request from the CPU1 or terminals 3 at this time, the control circuit information circuit XR2-3 adds one to the circuit information to monitor the requests repeatedly. When there is a request, the requested circuit information is used to control the requesting circuit.