Abstract: A CPU core includes an internal resource made up of various kinds of registers, and a controller having a bus control circuit which controls the input and output of data and others among various kinds of buses. A terminal group has a plurality of terminals for interconnecting the CPU core to a peripheral circuit and an external memory. The buses comprise an internal bus to which individual circuits incorporated in the CPU core are interconnected, a data bus interconnected between the CPU core and the external memory for allowing data to be inputted and outputted between the CPU core and the external memory, and a peripheral data bus inerconnected between the CPU core and the peripheral circuit for allowing data to be inputted and outputted between the CPU core and the peripheral circuit. The input and output terminals of all of the circuit portions which constitute the internal resource are interconnected to the internal bus.