| 摘要 |
PURPOSE:To preserve the storage contents of a RAM despite occurrence of an instantaneous service interruption by starting the back-up operation via a battery and transferring the storage contents to a saving RAM when a service interruption occurs. CONSTITUTION:A service interruption detecting circuit 10 which detects the service interruption of a power supply PS gives the information to status signal line ACFail, one of system buses when the AC voltage is set lower than a prescribed level. A battery 20 which inputs the status signal ACFail of the circuit 10 is charged in its energizing state and starts the back-up operation when a service interruption occurs, A saving RAM 30 having the approximately equal storage contents as a RAM is backed up by the battery 20 at the time of a service interruption. A saving command means 40 gives a command to transfer the storage contents of the RAM to the RAM 30 when a service interruption is detected by the circuit 10. The means 40 is usually stored in as ROM and called out and started by a CPU when a service interruption occurs. Thus the storage contents can be preserved until the service interruption is recovered. |
