| 摘要 |
Semiconductor integrated circuitry comprises an I/O circuit for activating an input/output of an internal circuit in response to an external power supply voltage applied thereto, a reference voltage generation circuit for decreasing the external power supply voltage so as to generate a constant reference voltage, a voltage drop circuit for controlling the external power supply voltage so as to decrease it such that it is equal to an input voltage applied thereto, and for supplying the decreased external power supply voltage to the internal circuit, and a mode determination control circuit to which a power supply voltage for test is supplied from a power supply for test that is connected to a power supply terminal for test in test mode, for comparing the power supply voltage for test with a threshold voltage so as to determine whether the semiconductor integrated circuitry is placed in either normal operation mode or the test mode, and for supplying either the reference voltage or the power supply voltage for test to the voltage drop circuit as the input voltage according to the mode determination result.
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