Abstract: An interface module for the operation of a chip card for data exchange between the chip card and a microprocessor system. The interface module includes circuits for communicating with the microprocessor system, communicating with the chip card in accordance with data and control instructions received from the microprocessor system, generating and/or controlling the chip card supply voltage, and for generating a clock signal which modified with respect to a clock frequency for the chip card from the clock pulse of a piezoelectric crystal oscillator. The interface module enable the microprocessor system to immediately control the chip card without the interconnection of another microprocessor.