A Near Field Communication Technology Type B Reader Device And A Reader Implemented Method Of Resolving Multiple NFC B Listen Devices

摘要

An NFC reader is embodied in a mobile phone (200) and adapted to implement a tag/PICS/ listen device resolution method by an NFC resolution sub-system (207). In accordance with the method reader slot controller (204) starts the resolution process by setting only one time slot in a first poll response signal resolution cycle. Consequently all the tags (D1-D4) receiving a poll request signal from the reader (200) send the poll response signal in the one available time slot causing a collision if there is more than one NFC-B tag in range. The method then increases the number of time slots (N) to be deployed in a next resolution cycle. A collision counter (205) counts the number of time slots in each collision cycle in which a collision is detected. A calculator then calculates a new number of time slots (N) to deploy in a subsequent collision resolution cycle. The calculation is N=2^Noc where NoC is the counted number of collisions. Thus the number of time slots can both increase and decrease.;The method enables the resolution of the last unresolved tag in range to be determined at the end of any resolution cycle in which no collisions are detected.