| 摘要 |
A data processing apparatus has a central processing unit. The CPU causes a memory to store for example input sales data in units of department sales and other items. When a power supply is turned off, a battery supplies back-up power supply voltage to the memory to retain the storage contents of the memory. When the output voltage from the battery is decreased to a value which disables back-up of the memory, is latch circuit is set. The latch circuit is held in the set state until it is forcibly reset. Even if the power source is turned on again, the CPU inhibits sales data input to the electronic register in response to an output signal from latch circuit, thereby preventing errors in the electronic register caused by invalid data in memory. |
