| 摘要 |
PURPOSE:To instruct CPUs that they select a memory which is used before until it is confirmed that copying in the on-line maintenance control is performed norm rally, by providing additionally dual shared memories and an instruction for comparing both systems. CONSTITUTION:If a memory device 5 (GMB) is faulty when a CPU 1 is in the holding state and CPUs 2 and 3 perform the on-line operation, the power source is turned off. A faulty part is replaced, and the GMB is set to the maintenance mode, and GMB preferentially selecting flags of CPUs 2 and 3 are turned off, and the power source is turned on again. The CPU 1 checks the writing and the reading of all areas of a GMA; and if the check result is good, the GMB is set to the on-line mode. Contents of the GMA are copied to the GMB. All areas of the GMA and the GMB are checked with the instruction for comparing both systems by comparison; and if the check result is good, GMB preferentially selecting flags of CPUs 2 and 3 are restored. The CPU 1 protects the GMB so that on-line CPUs 2 and 3 do not use the GMB until copying is completed. |
