| 摘要 |
<p>PURPOSE:To attain precise memory backup by controlling a capacitor so as not to charge the capacitor before depressing a reset switch on the basis of restoration of the contents of a RAM when the abnormality of a backup voltage is detected at ON of a control power supply. CONSTITUTION:When the control power supply Ei is turned off, the backup status of the RAM 6 by a charge voltage Ec is continued and the control volt age Ei is turned on at time t11 after dropping the charge voltage Ec less than a backup limit voltage level ec, the abnormality of backup is decided by a charge voltage deciding part 7 because the charge voltage Ec is less than the limit voltage level ec, abnormality information '1' is stored in an FF 8 by a power supply rise detecting pulse P and an abnormal signal S of '1' is outputted from the FF 8. The signal S outputted from the FF 8 is turned on a transistor (TR) 12 to by-pass a charge current ic to the capacitor 5. Once the abnormality is detected, charging to the capacitor 5 is inhibited until the reset operation of the FF 8 and the charging voltage of the capacitor 5 is almost kept 0V.</p> |
