an integrated circuit device comprises a pin for receiving a dc voltage component signal . the device comprises a signal source for applying an ac signal to the pin , a buffer for converting the ac signal into a digital signal , and a digital detector for detecting a frequency of the digital signal and outputting a predetermined detection signal . the predetermined detection signal is activated when the frequency of the digital signal is greater than or equal to a predetermined frequency . the predetermined detection signal is used as a signal for setting predetermined functional modes . the device further comprises registers or a differential amplifier and a decoder for generating a plurality of functional mode signals .