| 摘要 |
PROBLEM TO BE SOLVED: To enable a system to change a program to be executed by an optional central processing unit(CPU) and data to be referred to by the program to a new program and data as the system is in operation. SOLUTION: A CPU A1 informs a CPU B4 of the transfer of a new program and new data to switch the CPU B4 to a stand-by system. The CPU B4 switched to the stand-by system selectively receives the new program 46 and the new data 47 from the CPU A1 and restarts operation by the new program and data 46, 47. During the period, a CPU B3 continues its operation as an active system. When the operation of the CPU B4 succeeds, the CPUs B3, B4 are switched between the active system and the stand-by system, the program/data of the CPU B3 are also updated and returned to double constitution for synchronous operation. When the operation of the CPU B4 fails, operation based on the old program and data of the CPU B3 is continued.
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