Handheld device, smart card interface device (IFD) and data transmission method

A handheld device having an expansion slot which includes I/O ports, said handheld device characterized by comprising:

• means for driving said I/O ports;
• means for sending/receiving serial communication data signals and clock signals to/from said I/O ports;
• a smart card interface device connected to said expansion slot comprising:
• a host interface unit connected to said I/O ports, for receiving/sending serial communication data signals and clock signals from/to said I/O ports;
• a first smart card connector provided at a surface of said smart card interface device, for electrically connecting with a smart card of the first type;
• a first smart card interface unit for detecting whether a smart card of the first type has been connected to said first smart card connector and for driving the smart card of the first type being connected;
• a protocol implementation unit for controlling each component of said smart card interface device so as to implement communication protocols between said smart card interface device and said handheld device as well as communication protocols between said smart card interface device and said smart card of the first type.