| 摘要 |
PURPOSE:To maintain the contents of a RAM even if a power supply is turned off or a power supply voltage is instantaneously changed by executing memory backup operation when the power supply is turned off, and executing prescribed reset operation when the power supply is turned on. CONSTITUTION:If a dropped voltage level is reduced less than the power supply voltage VR for operating a system including an IC7, i.e. an one-chip MPU3 normally when the electronic instrument 2 including the one-chip MPU3 is turned to the operating state and the power supply voltage VA is changed from a prescribed value 5V to recessed state because of the instantaneous disconnection of the power supply on the way, an NMI terminal is turned to 'L' and an interruption processing routine is started to execute processing for receding necessary information into the RAM. When the power supply voltage VA is boosted again more than the power supply voltage VR without being dropped less than a lower threshold voltage V1, the output of the IC7 is turned to 'H' and the interruption mode is stopped. |
