PURPOSE: To eliminate a post-process at the CPU, by storing through the CPU the status information of an option device synchronously with the END signal or interruption signal outputted from the option device delivers at the end of its working.

CONSTITUTION: When an option device ends its process in the normal way, the option END signal 8 is sent to the CPU. The CPU produces the END signal 13 by the CPUEND signal 12 that is produced when an execution of instruction is over, and then stores the status information 10 given from the option device by the fall of signal 8 into the condition code part 14 of the program status word within CPU. In case an fault arises in the option device in the period to the end of process, the option interruption request signal 9 is sent to the CPU from the option device. Then the CPU stores the information 10 of the option device in the same way in synchronization with the fall of the signal 8.