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Abstract

In a radio frequency identification communication system, a communication protocol advantageously controls communication between an interrogator and one or more identifying labels or read/write tags. This protocol is configurable in two modes in which a read/write tag can be expected to operate. In the first mode, a rapid transfer of a limited amount of data takes place between the interrogator and one or more tags. In the second mode, a slower or less time critical transfer of a large quantity of data in a packet format takes place. In this second mode, a communication to the other tags causes these tags to remain 'silent' so that they do not corrupt the data transfer in progress. The interrogator automatically determines the quantity of data and the correct mode in which to operate. Either mode can be initiated on successive communication periods by the communication protocol. The data transfer may occur either from the interrogator to a tag or multiple tags, or from a selected tag or multiple tags to the interrogator. The protocol allows either mode to be executed interchangeably. A downlink synchronization signal is transmitted from the interrogator to the tag at regular intervals with a portion of the synchronization signal being used to control the subsequent data transfer mode.

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First Claim