Device and method for interface effective/ineffective state judging by varying threshold voltage to an input receiver circuit

摘要

The level of an input signal to an interface is judged at a first threshold value and a second threshold value. The first threshold value and the second threshold value are values within the amplitude range of the input signal. The first threshold value is higher than the input signal in a case where the interface is an ineffective state. The second threshold value is lower than the input signal in a case where the interface is in the ineffective state. If the interface is in the ineffective state, therefore, the result of the judgment of the level of the input signal at the first threshold value and the result of the judgment of the level of the input signal at the second threshold value differ from each other. It is judged whether the interface is in an effective state or in the ineffective state depending on whether or not the results differ from each other.