Patent ID: 7113547

Claim:
A data communication system comprising: a controller device; and a data carrier device connectable to said controller device through first and second contacts for performing data transfer between said controller device and said data carrier device, wherein said controller device includes: a power supply line for supplying power: a clock generation circuit for generating a clock pulse signal and supplying said clock pulse signal to at least one of said first and second contacts; a voltage level generation circuit for converting a voltage from said power supply line and supplying said converted voltage to said clock generation circuit as a first operation voltage; and a first transmitter circuit for changing said first operation voltage generated by said voltage level generation circuit in accordance with a first transmitting signal, and said data carrier device includes: a rectifier circuit for rectifying a voltage between said first and second contacts and supplying said rectified voltage to said data carrier device as a second operation voltage; a first signal detection circuit for detecting, as a first receiving signal, change of said second operation voltage having been rectified by said rectifier circuit; and a clock detection circuit for generating an operation clock on the basis of said clock pulse signal supplied to at least one of said first and second contacts.