CONTROL CIRCUIT

PROBLEM TO BE SOLVED: To provide a control circuit with which a microcomputer having a real time port(RTP) function can be provided without adding an address decoder for an RTP output register by allocating the same address to a port register and the RTP output register and holding data from a data bus in either the port register or the RTP output register corresponding to the value of an RTP control signal. SOLUTION: The same address is allocated to a port register 14 and an RTP output register 13 and data from a data bus 41 are held in either the port register 14 or the RTP output register 13 corresponding to the value of the RTP control signal so that the microcomputer having the RTP function can be provided without adding the address decoder for the RTP output register 13.