Abstract: By providing various functions in an X-terminal, the PCMCIA card controlling interface circuit supports various I/O functions through the same PCMCIA card that is used in personal computers. It also has more convenient and varied software support by using the PCMCIA memory card. In order to achieve this object, the PCMCIA card controlling interface circuit includes a clock signal generator, a PCMCIA card, a main processor, a bus interface, and a PCMCIA card controller. The clock-signal generator outputs a CLOCK signal. The PCMCIA card includes a number of memory card and I/O cards. The main processor outputs an address, a control signal and a driving signal to read and write to the PCMCIA card in accordance with a clock signal from said clock-signal generator.