| 摘要 |
PURPOSE: An interface for a semiconductor memory device is provided to reduce production costs by removing a switch such as a metal master of selecting a proper interface buffer circuit. CONSTITUTION: Interface unit for a semiconductor memory device includes an input buffer(21,22), a controller(23), and an output signal selector(24). The input buffer(21,22) includes at least two difference input buffers. The controller(23) includes a first inverter, a second inverter, a third inverter, and a resistor, and selects one of the input buffers according to an external reference signal. The first inverter inverts the external reference signal. The second inverter inverts an output signal of the first inverter, and feeds the inverting signal to an input terminal of the first inverter. The third inverter inverts an output signal of the latch. The resistor is connected between an output terminal of the latch and a power voltage terminal. The output signal selector includes a fourth inverter and many pass transistors. The fourth inverter inverts an output signal of the controller. The pass transistor receives an output signal of the controller, and transmits an output signal of the input buffer, and selects one of the output signals of the input buffers according to a control signal of the controller.
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