| 摘要 |
PURPOSE:To prevent data in a RAM from being changed by connecting resistors between an output control signal line and an external power supply connection line and between a write control signal line and the connection line and setting up the resistance value of the resistor connected to the output control signal line to a value larger than that connected to the write control signal line. CONSTITUTION:When an external power supply is impressed and potential is boosted, the potential of control signals in the output and write control signal lines 5, 6 start to be boosted, but since the resistance value of a resistor R1 is larger than that of a resistor R2, the increment of the potential of the control signal in the signal line 5 is delayed from that of the control signal in the signal line 6. Thereby, the control signal of the control line 6 is turned to an operation disabled level before the control signal of the signal line 5 is turned to the operation disabled level, so that the control signal of a write control signal 14 to the RAM 1 does not output the operatable level at the initial stage of the application of the external power supply and the data in the RAM 1 can be prevented from being changed. |
