System and method for data communication

The present invention relates to a serial data communication system and method between a main device and an external module connected thereto. Data communication system includes a main device; Is identified from the external module comprises the external module before performing the data communication, and transmits its identification information to the main device, the main device; and an external module for performing data communication is connected to the main device, after receiving the information, checking the connection of the external module, characterized in that the transmission to the external module identification signal on the identification information.