| 摘要 |
<p>PURPOSE:To reduce probability of erroneous write by fixing the output signal to a semiconductor memory device before each signal generated when a main power supply is interrupted, is turned to an instable state. CONSTITUTION:A voltage detection circuit 17 monitors the state of a main power source Vcc and outputs the stage while discriminating whether the main power source Vcc is equal to a fixed voltage or higher. When the main power source voltage Vcc is lower than the fixed voltage, an address signal to be inputted to the semiconductor memory device is fixed by a latch 20, a data signal is fixed by a latch 21 and a read/write control signal is fixed by a latch 22 and even when the main power supply Vcc is interrupted, the signal lines of these signals can be prevented from turning to the instable state. Thus, the data of the semiconductor memory device can be protected from the erroneous write caused by the instable state of the control signal line.</p> |
