A control chip of a card reader providing at least one card detection pin for detecting memory cards connected to corresponding read/write interfaces. The card detection pin is for the prevention of mutual interference caused by the memory cards connected with shared pins of the control chip. The card detection pin of the memory card may be used for the detection of another memory card being inserted into or pulled out from a read/write interface when the control chip of the card reader is accessing a memory card. An interference-acknowledgement signal is generated for the prevention or correction of accessing errors.