Anti-collision coupling for contactless cards

摘要

Contactless cards and a corresponding anti-collision coupling method are provided, where the method includes requesting that the cards transmit their unique identifiers that each include a fixed number of bytes, receiving the unique identifiers simultaneously as byte-wise positive pulses, counting the received positive pulses, and determining that more than one card responded if the number of received positive pulses exceeds the fixed number of bytes; and where the contactless cards each include a unique identifier having a number of bytes, a receiver for receiving an anti-collision command indicative of a desired identifier byte, a comparator in signal communication with the receiver for comparing the desired identifier byte with a corresponding byte of the unique identifier, and a transmitter responsive to the comparator for transmitting the unique identifier as byte-wise positive pulses if the desired identifier byte matches the corresponding byte of the unique identifier.

主权项

1. A method of detecting at least one contactless device that has a unique identification code (UID), the method comprising:
requesting transfer of a UID; receiving at least one positive pulse indicative of a UID; and detecting whether more than one UID was transferred if the number of positive pulses received exceeds the number expected for one UID, wherein when more than one UID was detected, the method further comprising: selecting a first UID byte from UID bytes determined from the received positive pulses; requesting transfer of a UID having the selected first UID byte; receiving at least one positive pulse indicative of a UID; and detecting whether more than one UID having the selected first UID byte was transferred if the number of positive pulses received exceeds the number expected for one UID, wherein when more than one UID having the selected first UID byte was detected, the method further comprising: selecting a second UID byte from UID bytes determined from the received positive pulses; requesting transfer of a UID having the selected first UID byte and the selected second UID byte; receiving at least one positive pulse indicative of a UID; and detecting whether more than one UID having the selected first UID byte and the selected second UID byte was transferred if the number of positive pulses received exceeds the number expected for one UID.