| 摘要 |
PURPOSE:To improve using efficiency by switching two storage devices enabled to set up independently address spaces by a utility or waiting mode to use each storage device and using these storage devices with doubled constitution only at a part matching respective addresses and with a single constitution at other parts. CONSTITUTION:Two storage devices 11, 11' are divided into three blocks 1A- 3A, 1B-3B respectively and both the devices 11, 11' can set up address spaces independently. An output of an address decode and an address selecting signal group are selected so that an optional block out of the blocks 1A-3A of the storage device 11 and an optional block out of the blocks 1B-3B in the storage device 11' are set up in the same address space. If abnormality is generated in both the storage elements of respective storage devices 11, 11', the device including a normal storage elememt at the same address is always switched to the utility side and the operation can be continued only when both the abnormal storage elements are not set up on the same address. Since these devices are doubled partially, the using efficiency is improved. |
