PURPOSE: To simplify a device and ensure an accurate writing of data, by securing the same period between the write pulse signal and the WE clocksignal and then performing a renewing process of the access address when a coincidence is obtained between the execution step and the write mode selected previously.

CONSTITUTION: For a history control system in which the internal state information of a system is written on a history memory 1 in a desired mode in case a fault diagnosis of the system is carried out, an renewal process of the access address is carried out to the memory 1 when a coincidence is obtained between the system execution mode and the write mode selected previously. At the same time, a write pulse signal 3' indicating the write timing to the memory 1 is produced with every write enable WE clock, and the internal state information in a write mode selected previously is written onto the memory 1. Thus the constitution can be simplified without exercising any special control over the production of the write pulse signal.