A data communication system applied in an Inter-Integrated Circuit (I2C) bus serving more than one master device includes a first master device, a second master device, and a logic control unit. The logic control unit receives serial data line (SDA) signal and serial clock line (SCL) signal from the I2C bus of the first master device and of the second master device, and determines a priority between the first master device and the second master device, control of the I2C bus without prejudicing any current messaging is allocated accordingly. A data communication method is also provided.
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