Input sense circuit having selectable thresholds

A semiconductor integrated circuit comprising:

• an input signal terminal to which an input signal is supplied from an outer unit;
• a first and a second input voltage sensing circuits each having a different circuit threshold value and connected to said input signal terminal, for sensing whether a voltage of said input signal is higher or lower than a predetermined normal level;
• a power supply voltage sensing circuit for sensing whether a power supply voltage applied from outer unit is a normal power supply voltage or a voltage different from said normal power supply voltage;
• a selection circuit for selecting a corresponding one from said first and said second input voltage sensing circuits in accordance with the output of said power supply sensing circuit;
• and
• an internal circuit to which an output of a selected one of said input voltage sensing circuits is connected,
• wherein said first input voltage sensing circuit comprises a first PMOS transistor having a source to which said input signal terminal is connected, a gate to which said power supply voltage is applied and a first gate threshold voltage, a first switching circuit connected between a drain of said first PMOS transistor and an input terminal of said internal circuit, and a resistor element connected between the input terminal of said internal circuit and a reference voltage;
• said second input voltage sensing circuit comprises a second PMOS transistor having a source to which said input signal terminal is connected, a gate to which said power supply voltage is applied and a second gate threshold voltage, a second switching circuit connected between a drain of said second PMOS transistor and an input terminal of said internal circuit;
• and
• said selection circuit is a switch controlling circuit for controlling said first and said second switching circuits to be selectively turned on and off in accordance with the output of said power supply voltage sensing circuit.