Tag inventorying based on memory-mapped flags

Abstract

An RFID tag IC implements several volatile flags, each of which can be mapped to one or more nonvolatile memory locations in the RFID tag IC. Memory-mapped volatile flags can be accessed directly, such as by specifying the flag in a Query command, or indirectly, such as by specifying the memory location that the flag is mapped to in appropriate fields of a Select command. When a command received from an RFID reader specifies a volatile flag using its memory-mapped location, the RFID tag IC is configured to refer to the current state or value of the volatile flag to proceed with the command.

Description

TAG INVENTORYING BASED ON MEMORY-MAPPED FLAGSCROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims priority to U.S. Provisional Patent Application Ser. No. 63 / 61 1,411 filed on December 18, 2023. The disclosures of the Provisional Application are hereby incorporated by reference in their entirety.BACKGROUND

[0002] Radio-Frequency Identification (RFID) systems typically include RFID readers, also known as RFID readcr / writers or RFID interrogators, and RFID tags. RFID systems can be used in many ways for locating and identifying objects to which the tags are attached. RFID systems are useful in product-related and service-related industries for tracking objects being processed, inventoried, or handled. In such cases, an RFID tag is usually attached to an individual item, or to its package.

[0003] In principle, RFID techniques entail using an RFID reader to inventory one or more RFID tags, where inventorying involves singulating a tag, receiving an identifier from a tag, and / or acknowledging a received identifier (e.g., by transmitting an acknowledge command). “Singulated” is defined as a reader singling-out one tag, potentially from among multiple tags, for a reader-tag dialog. “Identifier" is defined as a number identifying the tag or the item to which the tag is attached, such as a tag identifier (TID), electronic product code (EPC), etc. The reader transmitting a Radio- Frequency (RF) wave performs the interrogation. The RF wave is typically electromagnetic, at least in the far field. The RF wave can also be predominantly electric or magnetic in the near or transitional near field. The RF wave may encode one or more commands that instruct the tags to perform one or more actions.

[0064] In typical RFID systems, an RFID reader transmits a modulated RF inventory signal (a command), receives a tag reply, and transmits an RF acknowledgement signal responsive to the tag reply. A tag that senses the interrogating RF wave may respond by transmitting back another RF wave. The tag either generates the transmitted back RF wave originally, or by reflecting back a portion of the interrogating RF wave in a process known as backscatter. Backscatter may take place in a number of ways.

[0005] Th e reflected-baek RF wave may encode data stored in the tag, such as a number. The response is demodulated and decoded by the reader, which thereby identifies, counts, or otherwise interacts with the associated item. The decoded data can denote a serial number, a price, a date, a lime, a destination, an encrypted menage, an electronic signature, other attribute( s). ait) combination of attributes, and so on. Accordingly, when a reader receives tag data it can leam about the item that hosts the tag and / or about the tag itself

[0006] An RFID lag typically includes an antenna section, a radio section, a powermanagement section, and frequently a logical section, a memory, or both. In some RFID tags the pow er-management section nc I tided an energy storage dev ice such as a batter) . Ki ll) tags w ith an cnerg) storage device are know n as batter) -assisted. semiactive. nr active tags, Other I D lags can be powered solely by the R F signal they receive. Such RFID tags do not include an energy storage device and are called passive tags. Of course, even passive tags typically include temporary energy- and data flag-storage elements such a> capacitors or inductors. v BRIEF

[0007] This summary is provided to introduce a selection of concepts in a simplified form that are further described below in the Detailed Description. This summary is not intended to identify key features or essential features of the claimed subject matter, nor is it intended as an aid in determining the scope of the claimed subject matter.

[0008] I mbodimenis are directed to inventorying R! Il ) tags using memory-mapped volatile flags. 'Volatile session flags may be mapped to designated nonvolatile memory locations in an RFID tag, such that values at the designated / memory locations appear to correlate with whether the corresponding session flags are asserted or not. T his may allow RFID tags to be inventoried based on the values of two or more volatile session flags simultaneously. For example, one session Hag may be used to track whether tags should even participate in inventorying, while another session flag may be used to track the progress of the inventorying.Examples are directed to a method for an / RFID IC to access a first volatile flag having a first flag identifier and mapped to a first nonvolatile mentory location and a second volatile flag having a second flag identifier and mapped to a secondnonvolatile memory location. The method may include receiving, via a transceiver of the RFID IC, a first command having a pointer value specifying the first nonvolatile memory location and a mask value having a first bit and a second bit The first bit may correspond to the first volatile flag and the second bit may correspond to the second volatile flag. In response to receiving the first command, the RFID IC may access both the first and second volatile flags. The RFID IC may then receive, via the transceiver, an inventorying command specifying one of the first and second flag identifiers. In response to receiving the inventorying command, the RFID IC may access the volatile flag corresponding to the flag identifier specified by the first inventorying command.

[0010] Other examples are directed to an RFID IC including a memory. The RFID IC may have a first volatile flag having a first flag identifier and mapped to a first nonvolatile memory location. The RFID IC may also have a second volatile flag having a second flag identifier and mapped to a second nonvolatile memory location. The RFID IC may further include a transceiver that is configured to receive and respond to commands. The RFID IC may also include a processing block that is coupled to the memory, the first volatile flag, the second votetile flag, and the transceiver. The processing block can be configured to perform methods for the RFID IC to access the first volatile flag and the second volatile flag.

[0011] These and other features and advantages will be apparent from a reading of the following detailed description and a review of the associated drawings. It is to be understood that both the foregoing general description and the following detailed description are explanatory only and are not restrictive of aspects as claimed.BRIEF DESCRIPTION OF THE DRAWINGS

[0912] The following Detailed Description proceeds with reference to the accompanying drawings, in which:

[0013] FIG. 1 is a block diagram of components of an RFID system.

[0014] FIG. 2 is a diagram showing components of a passive RFID tag, such as a tag that can be used in the system of FIG. 1.

[0015] FIG, 3 is a conceptual diagram for explaining a half-duplex mode of communication between the components of the RFID system of FIG. 1.

[0016] FIG. 4 is a block diagram showing a detail of an RFID tag, such as the one shown in FIG. -2

[0017] FIG. 5A and 5B illustrate signal paths during tag-to-reader andreader-to-tag communications in the block diagram of FIG. 4.

[0018] FIG. 6 is a block diagram showing a detail of an RFID reader system, such as the one shown in FIG. 1.

[0019] FIG. 7 is a block diagram illustrating an overall architecture of an RFID system according to embodiments.

[0020] FIG. 8 is a diagram of an example RFID tag IC memory configuration, according to embodiments.

[0021] FIG. 9 illustrates fields of a Select command according to the Gen2 Protocol.

[0022] FIG. 10 illustrates example tag actions in response to a Select command with various “Action” field values, according to the Gen2 Protocol.

[0023] FIG. 11 is a table illustrating the persistence times of various flags, according to the Gen2 Protocol.

[0024] FIG. 12 illustrates fields of a Query command according to the Gen2 Protocol.

[0025] FIG. 13 illustrates an example implementation environment for quieting RFID tags using memory-mapped flags, according to embodiments.

[0026] FIG. 14 is a flow diagram ofa method for an RFID tag to access both a first volatile flag and a second votetile flag, according to embodiments.

[0027] FIG. 15 is a flow diagram of a method for an RFID tag to access a first volatile flag, according to embodiments.

[0028] FIG. 16 is a flow diagram of a method for inventorying RFID tags using a memory-mapped flag, according to embodiments.,

[0829] FIG. 17 is flow diagram of a method for inventorying RFID tags using memory-mapped flags, according to embodiments.DETAILED DESCRIPTION

[0030] In the following detailed description, references are made to the accompanying drawings that form a part hereof, and in which are shown by way ofillustration specific embodiments or examples. These embodiments or examples may be.combined, other aspects may be utilized, and structural changes may be made without departing from the spirit or scope of the present disclosure. The following detailed description is therefore not to be taken in a limiting sense, and the scope of the present invention is defined by the appended claims and their equivalents.

[0031] As used herein, “memory” is one of ROM, RAM, SRAM, DRAM, NVM, EEPROM, FLASH, Fuse, MRAM, FRAM, and other similar volatile and nonvolatile information-storage technologies as will be known to those skilled in the art. Some portions of memory may be writeable and some not. “Command” refers to a reader request for one or more tags to perform one or more actions, and includes one or more tag instructions preceded by a command identifier or command code that identifies the command and / or the tag instructions. “Instruction” refers to a request to a tag to perform s single explicit action (e.g., write data into memory). “Program” refers to a request to a tag to perform a set or sequence of instructions (e.g.» read a value from memory and, if the read value is less than a threshold then lock a memory word). “Protocol” refers to an industry standard for communications between a reader and a tag (and vice versa), such as the Class- 1 Generation-2 UHF RFID Protocol for Communications at 860 MHz - 960 MHz by GS 1 EPCglobal, Inc. (“Gen2 Protocol”), versions 1.2.0, 2.0, and 3.0 of which are hereby incorporated by reference.

[0032] When inventorying RFID tags, it is generally desired to keep the tags that have already been inventoried relatively quiet so that tags that have not yet been inventoried are visible. During a particular inventorying procedure, a session flag can boused to track whether a tag has already been inventoried or not. An example of a Session flag is an inventoried flag as described by foe Gen2 Protocol. The Gen2 Protocol specifies four inventoried flags S0, S1, S2, and S3 (also referred to as ‘session flags*) of four unique inventorying Sessions and a selected flag. A flag can be either in an unassorted state, often referred to as an “A” or “0” value, or in an asserted state, often referred to as a “B” or “I” value. When inventorying tags, an RFID reader can decide which session flag to use to track the inventorying process, and which state or value of the flag indicates foal a tag has been inventoried. For example, an RFID reader may decide that all inventoried tags will have an S0 flag value of “B” This implies that uninventoried tags will have S0 flag values of “A”, and upon inventorying a certain tag, the reader will cause the tag to change its S0 flag to “B".

[0033] As mentioned above, an RFID reader may want to “quiet” certain, already- inventoried tags, allowing tags that have not been “quieted” to be inventoried in the inventorying round. In general, the session flag used for inventorying cannot be used to trade something else such as tag quieting, because it is being actively used to track inventory ing. Accordingly, another means may be needed to track tag quieting.

[0034] Further, sometimes tags are quieted that should not be quieted. This may occur because of, for example, a glitch in software or a change in tag destination. These tags need to be identified and unquieted, without unquieting tags that should not be unquieted.(0035] FIG. 1 is a diagram of the components of a typical RFID system 100, incorporating embodiments. An RFID reader 1 10 transmits an interrogating RF signal 112.. RFID tag 120 in the vicinity of RFID reader 110 senses interrogating RF signal 112 and generates signal 126 in response. RFID reader 110 senses and interprets signal 126. The signals 112 and 126 may include RF waves and / or non-propagating RF signals (e.g., reactive near-field signals).

[0036] Reader 1 10 and tag 120 communicate via signals 112 and 126. When communicating, each encodes, modulates, and transmits data to the other, and each receives, demodulates, and decodes data from the other. The data can be modulated onto, and demodulated from, RF waveforms. The RF waveforms are typically in a suitable range of frequencies, such as those new 900 MHz, 13.56 MHz, and so on.

[0037] The communication between reader and tag uses symbols, also called RFID symbols. A symbol can be a delimiter, a calibration value, and so on. Symbols can be implemented for exchanging binary data, such as “0” and “1 ”, if that is desired. When symbols are processed by reader 110 and tag 120, they can be treated as values, numbers, and so on.(0038] Tag 120 can be a passive tag, or an active or battery-assisted tag (i.e., a teg having its own power source). When tag 120 is a passive tag, it is powered from signal 1 12.

[0039] FIG. 2 is a diagram of an RFID tag 220, which may function as tag 120 of FIG. 1. Tag 220 is drawn as a passive tag, meaning it does not have its own power source. Much of what is described in this document, however, applies also to active and battery-assisted tags.

[0040] Tag 220 is typically (although not necessarily) formed on a substantially planar inlay 222, which can be made in many ways known in the art. Tag 220 includes a circuit which may be implemented as an IC 224, In some embodiments IC 224 is implemented in complementary metal-oxide semiconductor (CMOS) technology. In other embodiments IC 224 may be implemented in other technologies such as bipolar junction transistor (BJT) technology, metal-semiconductor field-effect transistor (MESFET) technology, and others as will be well known to those skilled in the art IC 224 is arranged on inlay 222.

[0041] Tag 220 also includes an antenna for exchanging wireless signals with its environment. The antenna is often flat and attached to inlay 222. IC 224 is electrically coupled to the antenna via suitable IC contacts (not shown in FIG. 2). The term “electrically coupled” as used herein may mean a direct electrical connection, or it may mean a connection that includes one or more intervening circuit Hocks, elements, or devices. The “electrical” part of the term “electrically coupled” as used in this document shall mean a coupling that is one or more of ohmic / galvanic, capacitive, and / or inductive. Similarly, the terms “electrically isolated” or “electrically decoupled” as used herein mean that electrical coupling of one or more types (e.g., galvanic, capacitive, and / or inductive) is not present, at least to the extent possible. For example, elements that are electrically isolated from each other are galvanically isolated from each other, capacitively isolated from each other, and / or inductively isolated from each other. Of course, electrically isolated components will generally have some unavoidable stray capacitive or inductive coupling between them, but the intent of the isolation is to minimize this stray coupling to a negligible level when compared with an electrically coupled path.

[0042] IC 224 is shown with a single antenna port, comprising two IC contacts electrically coupled to two antenna segments 226 and 228 which are shown here forming a dipole. Many other embodiments are possible using any number of ports, contacts, antennas, and / or antenna segments.

[0043] Diagram 250 depicts top and side views of tag 252, formed using a strap. Tag 252 differs from tag 220 in that it includes a substantially planar strap substrate 254 having strap contacts 256 and 258. IC 224 is mounted on strap substrate 254 such that the IC contacts on IC 224 electrically couple to strap contacts 256 and 258 via suitable connections (hot shown). Strap substrate 254 is then placed on inlay 222 suchthat strap contacts 256 and 258 electrically couple to antenna segments 226 and 228.- Strap substrate 254 may be affixed to inlay 222 via pressing, an interface layer, one or more adhesives, or any other suitable means.

[0044] Diagram 260 depicts a side view of an alternative way to place strap substrate 254 onto inlay 222. Instead of strap substrate 254’s surface, including strap contacts 256 / 258, facing the surface of inlay 222, strap substrate 254 is placed with its strap contacts 256 / 258 facing away from the surface of inlay 222. Strap contacts 256 / 258 can then be either capacitively coupled to antenna segments 226 / 228 through strap substrate 254, or conductiveiy coupled using a through-via which may be formed by crimping strap contacts 256 / 258 to antenna segments 226 / 228. In some embodiments, the positions of strap substrate 254 and inlay 222 may be reversed, with strap substrate 254 mounted beneath inlay 222 and strap contacts 256 / 258 electrically coupled to antenna segments 226 / 228 through inlay 222. Of course, in yet other embodiments strap Contacts 256 / 258 may electrically couple to antenna segments 226 / 228 through both inlay 222 and strap substrate 254.

[0045] In operation, the antenna receives a signal and communicates it to IC 224, which may both harvest power and respond if appropriate, based on the incoming signal and the iC’s internal state. If IC 224 uses backscatter modulation, then it responds by modulating the antenna’s reflectance, which generates response signal 126 from signal 1 12 transmitted by the reader. Electrically coupling and uncoupling the IC Contacts of IC 224 can modulate the antenna’s reflectance, as can varying the admittance of a shunt-connected circuit dement which is coupled to the IC contacts. Varying the impedance of a series-connected circuit element is another means of modulating the antenna's reflectance. If IC 224 is capable of transmitting signals (e.g., has its own power source, is coupled to an external power source, and / or is able to harvest sufficient power to transmit signals), then IC 224 may respond by transinitting response signal 126.

[0046] In the embodiments of FIG. 2, antenna segments 226 and 228 are separate from IC 224. In other embodiments, the antenna segments may alternatively be formed on IC 224. Tag antennas according to embodiments may be designed in any form and are not limited to dipoles. For example, the tag antenna may be a patch, a slot, a loop, a coil, a hom, a spiral, a monopole, microstrip, stripline, or any other suitable antenna.

[0047] An RFID tag such as tag 220 is often attached to or associated with an individual item or the item packaging. An RFID tag may be fabricated and then attached to the item or packaging, or may be partly fabricated before attachment to the item or packaging and then completely fabricated upon attachment to the item or packaging. In some embodiments, the manufacturing process of the item or packaging may include the fabrication of an RFID tag, In these embodiments, the resulting RFID tag may be integrated into the item or packaging, and portions of the item or packaging may serve as tag components. For example, conductive item or packaging portions may serve as tag antenna segments or contacts. Nonconductive item or packaging portions may serve as tag substrates or inlays. If the item or packaging includes integrated circuits or other circuitry, some portion of the circuitry may be configured to operate as part or all of an RFID tag IC. An “RFID IC” may refer to an item capable of receiving and responding to RFID signals. For example, an item having a separate but attached RFID tag can be considered an RFID IC, as is an item having an integrated RFID tag or an item manufactured to have the capabilities of an RFID tag. A standalone RFID tag may also be referred to as an “RFID IC".

[0048] The components of the RFID system of FIG. 1 may communicate with each other in any number of modes. One such mode is called full duplex, where both reader 110 and tag 120 can transmit at the same time. In some embodiments, RFID system 100 may be capable of full duplex communication if tag 120 is configured to transmit signals as described above. Another such mode, suitable for passive tags, is called half-duplex, and is described below.

[0049] FIG. 3 is a conceptual diagram 300 for explaining half-duplex communications between the components of the RFID system of FIG. I , in this case with tag 120 implemented as passive tag 220 of FIG. 2. The explanation is made with reference to a TIME axis, and also to a human metaphor of “talking" and “listening". The actual technical implementations for “talking" and ‘listening" are now described.

[0050] RFID reader 110 and RFID tag 120 talk and listen to each other by taking turns. As seen on axis TIME, when reader 110 talks to tag 120 the communication session is designated as “R->T”, and when tag 120 talks to reader 110 the communication session is designated as “T->R”. Along the TIME axis, a sample R->T communication session occurs during a time interval 312, and a following sample T->R communication session occurs during a time interval 326. Interval 312may typically be of a different duration than interval 326 - here the durations are shown approximately equal only for purposes of illustration.

[0051] According to blocks 332 and 336, RFID reader 110 talks during interval 312, and listens during interval 326. According to blocks 342 and 346, RFID tag 120 listens while reader 110 talks (during interval 312), and talks while reader 1 10 listens (during interval 326).

[0052] In terms of actual behavior, during interval 312 reader 110 talks to tag 120 as follows, According to block 352, reader 110 transmits signal 112, which was first described in FIG. 1. At the same time, according to block 362, tag 120 receives signal 1 12 and processes it to extract data and so on. Meanwhile, according to block 372, tag 120 does not backscatter with its antenna, and according to block 382, reader 1 10 has no signal to receive from tag 120.

[0053] During interval 326, which may also be referred to as a backscatter time interval or backscatter interval, tag 120 talks to reader 110 as follows. According to block 356, reader 110 transmits a Continuous Wave (CW) signal, which can be thought of as a carrier that typically encodes no information. This CW signal serves both to transfer energy to tag 120 for its own internal power needs, and also as a carrier that tag 120 can modulate with its backscatter. Indeed, during interval 326, according to block 366, tag 120 does not receive a signal for processing. Instead, according to block 376, tag 120 modulates the CW emitted according to block 356 so te to generate backscatter signal 126, for example by adjusting its antenna reflectance. Concurrently, according to block 386, reader 110 receives backscatter signal 126 and processes it

[0054] FIG. 4 is a block diagram showing a detail of an RFID IC, such as 1C 224 in FIG. 2. Electrical circuit 424 in FIG. 4 may be formed in an IC of an RFID tag, such as tag 220 of FIG. 2. Circuit 424 has a number of main components that are described in this document. Circuit 424 may have a number of additional components from what is shown and described, or different components, depending on the exact implementation.

[0055] Circuit 424 shows two IC contacts 432, 433, suitable for coupling to antenna segments such as antenna segments 226 / 228 of RFID tag 220 of FIG. 2. When two IC contacts form the signal input from and signal return to an antenna they are oftenreferred-to as an antenna port IC contacts 432, 433 may be made in any suitable way, such as from metallic pads and so on. In some embodiments circuit 424 uses more than two IC contacts, especially when tag 220 has more than one antenna port and / or more than one antenna.

[0096] Circuit 424 includes signal-routing section 435 which may include signal wiring, signal-routing busses, receive / transmit switches, and so on that can route a signal to the components of circuit 424. In some embodiments IC contacts 432 / 433 couple galvanically and / or inductively to signal-routing section 435. In other embodiments (such as is shown in FIG. 4) circuit 424 includes optional capacitors 436 and / or 438 which, if present, capacitively couple IC contacts 432 / 433 to signalrouting section 435. This capacitive coupling causes IC contacts 432 / 433 to be galvanically decoupled from signal-routing section 435 and other circuit components.

[0057] Capaciti ve coupling (and resultant galvanic decoupling) between IC contacts 432 and / or 433 and components of circuit 424 is desirable in certain situations. For example, in some RFID tag embodiments IC contacts 432 and 433 may galvanically connect to terminals of a tuning loop on the tag. In this situation, capacitors 436 and / or 438 galvanically decouple IC contact 432 from IC contact 433, thereby preventing the formation of a short circuit between the IC contacts through the tuning loop.

[0058] Capacitors 436 / 438 may be implemented within circuit 424 and / or partly or completely external to circuit 424. For example, a dielectric or insulating layer on the surface of the IC containing circuit 424 may serve as the dielectric in capacitor 436 and / or capacitor 438. As another example, a dielectric or insulating layer on the surface of a tag substrate (e.g., inlay 222 or strap substrate 254) may serve as the dielectric in capacitors 436 / 438. Metallic or conductive layers positioned on both sides of the dielectric layer (i.e., between the dielectric layer and the IC and between the dielectric layer and the tag substrate) may then serve as terminals of the capacitors 436 / 438, The conductive layers may include IC contacts (e.g., IC contacts 432 / 433), antenna segments (e.g., antenna segments 226 / 228), or any other suitable conductive layers.

[0059] Circuit 424 also includes a rectifier and PMU (Power Management Unit) 441 that harvests energy from the RF signal received by antenna segments 226 / 228 topower the circuits of IC 424 during either or both reader-to-tag (R->T) and tag-to- reader (T->R) sessions. Rectifier and PMU 441 may be implemented in any way known in the art, and may include one or more components configured to convert an alternating-current (AC) or time-varying signal into a direct-current (DC) or substantially time-invariant signal.

[0060] Circuit 424 additionally includes a demodulator 442 that demodulates the RF signal received via IC contacts 432, 433. Demodulator 442 may be implemented in any way known io the art, for example including a slicer, an amplifier, and so on.

[0061] Circuit 424 further includes a processing block 444 that receives the output from demodulator 442 and performs operations such as command decoding, memory interfacing, and so on. In addition, processing block 444 may generate an output signal for transmission. Processing block 444 may be implemented in any way known in the art, for example by combinations of one or more of a processor, memory, decoder, encoder, and so on.

[0962] Circuit 424 additionally includes a modulator 446 that modulates an output signal generated by processing block 444. The modulated signal is transmitted by driving IC contacts 432, 433, and therefore driving the load presented by the coupled antenna segment or segments. Modulator 446 may be implemented in any way known in the art, for example including a switch, driver, amplifier, and so on.

[0063] In one embodiment, demodulator 442 and modulator 446 may be combined in a single transceiver circuit In another embodiment modulator 446 may modulate a signal using backscatter, in another embodiment modulator 446 may include an active transmitter. In yet other embodiments demodulator 442 and modulator 446 may be part of processing block 444.

[0064] Circuit 424 additionally includes a memory 450 to store data 452. At least a portion of memory 450 is preferably implemented as a nonvolatile memory (NVM), which means that data 452 is retained even when circuit 424 does not have power, as is frequently the case for a passive RFID tag.

[0065] In some embodiments, particularly in those with more than one antenna port, circuit 424 may contain multiple demodulators, rectifiers, PMUs, modulators, processing blocks, and / or memories.

[0666] In terms of processing a signal, circuit 424 operates differently during a R->T session and a T ->R session. The different operations are described below, in this case with circuit 424 representing an IC of an RFID lag,

[0067] FIG. 5A shows version 524- A of components of circuit 424 of FIG. 4. further modified to emphasize a signal operation during a R->T session during time interval 312 of FIG. 3. Demodulator 442 demodulates an RF signal received from IC contacts 432, 433. The demodulated signal is provided to processing block 444 as C JN. In one embodiment, C_IN may include a received stream of symbols.

[0068] Version 524-A shows as relatively obscured those components that do not play a part in processing a signal during a R->T session. Rectifier and PMU 441 may be active, such as for converting RF power. Modulator 446 generally does not transmit during a R->T session, and typically does not interact with the received RF signal significantly, either because switching action in section 435 of FIG. 4 decouples modulator 446 from the RF signal, or by designing modulator 446 to have a suitable impedance, and so on.

[0069] Although modulator 446 is typically inactive during a R->T session, it need not be sb. For example, during a R->T session modulator 446 could be adjusting its own parameters for Operation in a future session, and so on.

[0070] FIG. 5B shows version 524-B of components of circuit 424 of FIG. 4, further modified to emphasize a signal operation during a T->R session during time interval 326 of F1G. 3. Processing block 444 outputs a signal C_OUT. In one embodiment, C_OUT may include a stream of symbols for transmission. Modulator 446 then modulates C_OUT and provides it to antenna segments such as segments 226 / 228 of RFID tag 220 via IC contacts 432, 433,

[0071] Version 524-B shows as relatively obscured those components that do not play a part in processing a signal during a T->R session. Rectifier and PMU 441 may be active, such as for converting RF power. Demodulator 442 generally does not receive during a T->R session, and typically does not interact with the transmitted RF signal significantly, either because switching action in section 435 of FIG. 4 decouples demodulator 442 from the RF signal, or by designing demodulator 442 to have a suitable impedance, and so on.

[0072] Although demodulator 442 is typically inactive during a T->R session, it need not be so. For example, during a T->R session demodulator 442 could be adjusting its own parameters for operation in a future session, and so on.

[0073] In typical embodiments, demodulator 442 and modulator 446 are operable to demodulate and modulate signals accordingto a protocol, such as the Gen2 Specification mentioned above. In embodiments where circuit 424 includes multiple demodulators and / or modulators, each may be configured to support different protocols or different sets of protocols. A protocol specifies, in part, symbol encodings, and may include a set of modulations, rates, timings, or any other parameter associated with data communications. In addition, a protocol can be a variant of a stated specification such as the Gen2 Specification, for example including fewer or additional commands than the stated specification calls for, and so on. In Mich instances, additional commands aresometimes called custom commands.

[0074] FIG. 6 is a block diagram of an RFID reader system 600 according to embodiments. RFID reader system 600 includes a local block 610, and optionally remote components 670, Local block 610 and remote components 670 can be implemented in any number of ways. For example, local block 610 or portions of local block 610 may be implemented as a standalone device or as a component in another device. In some embodiments, local block 610 or portions of local block 610 may be implemented as a mobile device, such as a handheld RFID reader, or as a component in a mobile device, such as a laptop, tablet, smartphone, wearable device, or any other suitable mobile device. It will be recognized that RFID reader 110 of FIG. 1 is the same as local block 610, if remote components 670 are not provided. Alternately, RFID reader 1 10 can be implemented instead by RFID reader system 600, of which only the local block 610 is shown in FIG. 1.

[0075] In some embodiments, one or more of the Hocks or components of reader system 600 may be implemented as integrated circuits. For example, local block 610, one or moreof fee components of local block 610, and / or one or more of fee remote components 670 may be implemented as integrated circuits using CMOS technology, BJT technology, MESFET technology, and / or any other suitable implementation technology.

[0076] Local block 610 is responsible for communicating with RFID tags. Local block 610 includes a block 651 of an antenna and a driver of the antenna for communicating with the tags. Some readers, like that shown in local block 610, contain a single antenna and driver. Some readers contain multiple antennas and drivers and a method to switch signals among them, including sometimes using different antennas for transmitting and for receiving. Some readers contain multiple antennas and drivers that can operate simultaneously. In some embodiments, block 651 may be a phased-array antenna or synthesized-beam antenna (SB A), and local block 610 may be implemented in a synthesized-beam reader (SBR) configured to generate one or more beams via the SBA. A demodulator / decoder block 653 demodulates and decodes backscattered waves received from the tags via antenna / driver block 651. Modulator / encoder block 654 encodes and modulates an RF wave that is to be transmitted to the tags via antenna / driver block 651.

[0077] Local block 610 additionally includes an optional local processor 656. Local processor 656 may be implemented in any number of ways known m the art. Such ways include, by way of examples and not of limitation, digital and / or analog processors such as microprocessors and digital-signal processors (DSPs); controllers such as microcontrollers; software running in a machine such as a general purpose computer; programmable circuits such as Field Programmable Gate Arrays (FPGAs), Field-Programmable Analog Arrays (FPAAs), Programmable Logic Devices (PLDs), Application Specific Integrated Circuits (ASIC), any combination of one or more of these; and so on. In some cases, some or all of the decoding function in block 653, the encoding function in block 654, or both, may be performed instead by local processor 656. In some cases, local processor 656 may implement an encryption or authentication function; in some cases, one or more of these functions can be distributed among other blocks such as encoding block 654, or may be entirely incorporated in another block.

[0078] Local block 610 additionally includes an optional local memory 657. Local memory 657 may be implemented in any number of ways known in the art, including, by way of example and not of limitation, any of the memory types described above as well as any combination thereof. Local memory 657 can be implemented separately from local processor 656, or in an IC with local processor 656, with or without othercomponents. Local memory 657, if provided, can store programs for local processor 656 to run, if needed.

[0079] In some embodiments, local memory 657 stores data read from tags, or data to be written to tags, such as Electronic Product Codes (EPCs), Tag Identifiers (TlDs) and other data. Local memory 657 Can also include reference data that is to be compared to EPCs, instructions and / or rules for how to encode commands for the tags, modes for controlling antenna 651, encryption / authentication algorithms, algorithms for tracking tag location or movement, secret keys, key pairs, individual public and / or private keys, electronic signatures, and so on. In some of these embodiments, local memory 657 is provided as a database.

[0080] Some components of local block 610 typically treat the date as analog, such as the antenna / driver block 651. Other components such as local memory 657 typically treat the data as digital At some point, there is a conversion between analog and digital. Based on where this conversion occurs, a reader may be characterized as “analog” Or “digital”, but most readers contain a mix of analog and digital functionality.

[0081] If remote components 670 are provided, they are coupled to local block 610 via an electronic communications network 680. Network 680 can be a Local Area Network (LAN), a Metropolitan Area Network (MAN), a Wide Area Network (WAN), a network of networks such as the internet, or a local conununication link, such as a USB, PCI, and so oh. Local block 610 may include a local network connection 659 for communicating with communications network 680 or may couple to a separate device or component configured to communicate with communications network 680. Communications on the network can be Secure, such as if they are encrypted or physically protected, or insecure if they are not encrypted or otherwise protected.

[0082] There can be one or more remote components) 670. If more than one, they can be located at the same location, or in different locations. They may communicate with each other and local block 610 via communications network 680, or via other similar networks, and so on. Accordingly, remote components) 670 can use respective remote network connections. Only one such remote network connection 679 is shown, which is similar to local network connection 659, etc. In someembodiments, a single one of the remote components) 670 may be configured to communicate with and / or control multiple local blocks, each similar to local block 610.

[0083] Remote components) 670 can also include a remote processor 676. Remote processor 676 can be made in any way known hr the art, such as was described with reference to local processor 656, Remote processor 676 may also implement an encryption / authentication function and / or a tag location / tracking function, similar to local processor 656.

[0084] Remote components) 670 can also include a remote memory 677. Remote memory 677 can be made in any way known in the art, such as was described with reference to local memory 657. Remote memory 677 may include a local database, and a different database of a standards organization, such as one that can reference EPCs. Remote memory 677 may also contain information associated with commands, tag profiles, keys, or the like, similar to local memory 657.

[0085] One or more of the above-described elements may be combined and designated as operational processing block 690. Operational processing block 690 includes those components that are provided of the following: local processor 656, remote processor 676, local network connection 659, remote network connection 679, and by extension an applicable portion of communications network 680 that links remote network connection 679 with local network connection 659. The portion can be dynamically changeable, etc. In addition, operational processing block 690 can receive and decode RF waves received via antenna / driver 651 , and cause antenna / driver 651 to transmit RF waves according to what it has processed.

[0086] Operational processing block 690 includes either local processor 656, or remote processor 676, or both. If both are provided, remote processor 676 can be made such that it operates in a way complementary with that of local processor 656. In fact, the two can cooperate. It will be appreciated that operational processing block 690, as defined this way, is in communication with both local memory 657 and remote memory 677, if both are present.

[0087] Accordingly, operational processing block 690 is location independent, in that its. functions can be implemented either by local processor 656, or by remote processor 676, or by a combination of both. Some of these functions are preferablyimplemented by local processor 656, and some by remote processor 676. Operational processing block 690 accesses local memory 657, or remote memory 677, or both for storing and / or retrieving data.

[0088] RFID reader system 600 operates by operational processing block 690 generating communications for RFID tags. These communications are ultimately transmitted by antenna / driver block 651, with modulator / encoder block 654 encoding and modulating the information on an RF wave. Then data is received from the tags via antenna / driver block 651, demodulated and decoded by demodulator / decoder block 653, and processed by operational processing block 690.

[0089] Embodiments of an RFID reader system can be implemented as hardware, software, firmware, or any combination. Such a system may be subdivided into components or modules. Some of these components or modules can be implemented as hardware, some as software, some as firmware, and some as a combination. An example of such a subdivision is now described. together with the RFID tag as an additional module.

[0090] FIG. 7 is a block diagram illustrating an overall architecture of an RFID system 700 according to embodiments. RFID system 700 may be subdivided into modules or components, each of which may be implemented by itself or in combination with others. In addition, some of them may be present more than once. Other embodiments may be equivalently subdivided into different modules. Some aspects of FIG. 7 are parallel with systems, modules, and components described previously.

[0091] An RFID tag 703 is considered here as a module by itself. RFID tag 703 conducts a wireless communication 706 with the remainder, via the air interface 705. Air interface 705 is really a boundary, in that signals or data that pass through it are not intended to be transformed from one thing to another. Specifications as io how readers and tags are to communicate with each other, for example the Gen2 Specification, also properly characterize that boundary as an interface.

[0092] RFID system 700 includes one or more reader antennas 710, and an RF front- end module 720 for interfacing with reader antenna(s) 710. These can be made as described above. RFID system 700 also includes a signal-processing module 730. Inone embodiment, signal-processing module 730 exchanges waveforms with RF frontend module 720, such as I and Q waveform pairs.

[0093] RFID system 700 further includes a physical-driver module 740, which is also known as a data-link module. In some embodiments, physical-driver module 740 exchanges bits with signal-processing module 730. Physical-driver module 740carf be the stage associated with the framing of data.

[0094] RFID system 700 additionally includes a media access control module 750. In one embodiment, media access control layer module 750 exchanges packets of bits with physical driver module 740. Media access control layer module 750 can make decisions for sharing the medium of wireless communication, which in this case is the air interface.

[0095] RFID system 700 moreover includes an application-programming librarymodule 760. This module 760 can include application programming interfaces (APIs), other objects, etc.

[0096] All of these RFID system functionalities can be supported by one or more processors. One of these processors can be considered a host processor. Such a host processor might include a host operating system (OS) and / or central processing unit (CPU), as in module 770. In some embodiments, the processor is not considered as a separate module, but one that includes some of the above-mentioned modules of RFID system 700. In some embodiments, the one or more processors may perform operations associated with retrieving data that may include a tag public key, an electronic signature, a tag identifier, an item identifier, and / or a signing-authority public key. In some embodiments, the one or more processors may verify an electronic signature, create a tag challenge, and / Or verify a tag response.

[0097] User interface module 780 may be coupled to application-programming- library module 760, for accessing the APIs. User interface module 780 can be manual, automatic, or both. It can be supported by the host OS / CPU module 770 mentioned above, or by a separate processor, etc.

[0098] It will be observed that the modules of RFID system 700 form a chain. Adjacent modules in the chain can be coupled by appropriate instrumentalities for exchanging signals. These instrumentalities include conductors, buses, interfaces, andso on. These instrumentalities can be local, e.g. to connect modules that are physically close to. each other, or over a network, for remote communication.

[0099] The chain is used in one direction for receiving RFID waveforms and in the other direction for transmitting RFID waveforms. In receiving mode, reader antenna(s) 710 receives wireless waves, which are in turn processed successively by the various modules in the chain. Processing can terminate in any one of the modules. In transmitting mode, waveform initiation can be in any one of the modules. Ultimately, signals are routed to reader antenna(s) 710 to be transmitted as wireless waves.

[0100] The architecture of RFID system 700 is presented for purposes of explanation, and not of limitation. Its particular, subdivision into modules need not be followed for creating embodiments. Furthermore, the features of the presort disclosure can be performed either within a single one of the modules, or by a combination of them. In some embodiments RFID system 700 can be incorporated into another electronic device such as a checkout terminal in a store or a consumer device such as a mobile phohe.

[0101] FIG. 8 is a diagram 800 of an example RFID tag 1C memory configuration, according to embodiments. Diagram 800 depicts an RFID tag IC memory 850, like the physical memory configuration described in the Gen2 Protocol. Memory 850 includes four partitions, sections, or banks 852, 854, 856, and 858. Partition 852 (“User memory**) may be configured to store user data. Partition 854 (“TID memory”) may be configured to store an identifier for the tag IC itself, such as a tag identifier or TID. Partition 856 ("EPC memory”) may be configured to store an identifier for an item associated with or attached to the tag IC, such as an electronic product code Or EPC. Partition 858 (“Resaved memory’’) may be configured to store information reserved for the tag IC itself or otherwise not necessarily publicly accessible, such as passwords, PINs, Cryptographic keys, of similar. The Gen2 Protocol specifies that two passwords, the Access password and the Kill password, Can be stored in partition 858. The Access password, if present, can be used to restrict certain tag IC operations as described in the Gen2 Protocol. The Kill password, if present, can be used to cause a tag IC to enter the Killed state as described in the Gen2 Protocol. As these passwords are sensitive, partition 858 is generally not publicly accessible.

[0102] the configuration of tag IC memory 850 is provided as an example. Tag IC memory can have any number of partitions configured to store any suitable information. Tag IC memories are generally implemented using nonvolatile memory, although in some examples volatile memory may be used to implement tag IC memory.

[0103] FIG. 9 illustrates fields of a Select command according to the Gen2 Protocol. As described above, the Gen2 Protocol specifies four inventoried flags S0, S I, S2, and S3 (also referred to as session flags) and a selected flag SL. Any of toe flags can be either in an unassorted state, often referred to as an “A” or “0” value, or in an asserted state, often referred to as a “B” or “1” value. An RFID reader may populate fields 900 of a Gen2 Select command to cause RFID tags that meet certain criteria to assert or deassert certain flags, as specified by toe combination of the Action and target fields. One criterion is tag memory content, as specified by the combination of the MemBank, Pointer, Length, and Mask fields / When a tag receives a Select command, it checks to see if toe value specified in the Mask field matches toe value in the tag’s MemBank-specified memory bank starting at toe Pointer-specified memory location and having the Length-specified length. If so, then the tag “matches’ toe Select command. If not, then the tag does not “match” the Select command.

[0104] FIG. 10 illustrates example tag actions in response to a Select command with various “Action” field values, according to toe Gen2 Protocol. As mentioned above, a tag, upon receiving a Gen2 Select command, may determine whether it matches the Select command depending on whether it meets the criteria set forth in the command. If the tag determines that it matches toe Select command, then it performs the action in the “Tag Matching” column of table 1000 corresponding to the value of toe Action field in toe Select command, on toe flag specified by the Target field of the Select command. If toe tag determines that it does not match toe Select command, then it performs the action in the ‘Tag Not-Matching” column of table 1000 corresponding to the value of toe Action field in the Select command, on the flag specified by the Target field of the Select command. For example, suppose that a Select command has an Action field value of “000” and a Target field value of “100”. A tag receiving toe Select command may assert its selected flag SL if it matches, or deassert its selected flag SL if it doesn’t match. Suppose that toe Select command has toe same Action field value but instead had a Target field value of “001”. In this case, the receiving tagmay change its session flag S1 value to “A" if it matches, or to “B” if it doesn’t match.

[0105] Three examples of a tag performing an Action specified in a Select command are described below. For each of the below examples, consider a Select command, shortened for brevity, having the following fields: (Target, Action, MemBank, Pointer, Length, Mask).

[0106] In a first example, a tag may receive a first Select command having parameters: (Target= 100, Action=000, MemBank=01, Pointer= Length=00001000, Mask=00011010). After receiving the first Select command, the tag may access the EPC memory bank (specified by MemBank =01) and compare the tag memory content stored at a tag memory location starting at the first bit (specified by Pointer=00000000) having a length of eight (specified by Length=000001000) to the binary value “00011010“ (specified by Mask= 00011010). If the tag memory content at the tag memory location corresponds to tire Mask, then tire tag matches and may then perform the “Tag Matching" Action (specified by Action=000) of asserting the selected flag SL (specified by Target= 100) - i.e., setting the selected flag SL to “B" or “1”. If the tag memory content at the tag memory location does not correspond to the Mask, the tag does not match and may then perform the “Tag Not-Matching” Action of desserting the selected flag (i A, setting the SL flag to “A" or “0").

[0107] In a second example, a tag may receive a second Select command having parameters: (Target= 001, Action=011, Mem Bank = 10, Pointer=00000010 , Length=00000010, Mask = 11 After receiving the second Select command, the tag may access tire TID memory bank (specified by MemBank= 10) and compare the tag memory content stored at the tag memory location specified by the Pointer and Length values and to the Mask value - i.e., compare the tag memory contort starting at the second bit (specified by Pointer= 00000001 ) with a length of two bits (specified by Length= 00000010) to the binary value “1 P (specified by Mask=11). If the tag memory content at the tag memory location corresponds to the Mask, then the tag matches and may invert the session flag SI (specified by Target=001) - i.e., if SI is “A" then the Action “01 1 " for a matching tag causes the session flag Si to change to “B". If the tag memory content at the tag memory location does not correspond to the Mask value, then the tag does not match and may do nothing - i.e., hold SI at its current value.

[0108] In a third example, a tag may receive a third Select command. The third Select command may cause the tag to always perform an action, for example, by including parameters that the tag cannot match (referred to as ‘nonmatching parameters’), such as using Target, Action, and / or MemBank field values that point to a memory location that does not exist in the tag memory (e.g„ if the actual tag memory has 255 bits, the non-existing memory location may point to bit 300 which is out of range of the memory). After receiving the third Select command, which may be referred to as a nonmatching select command, the tag may determine that the memory location referenced by the nonmatching parameters cannot be accessed or does not exist in the tag memory. As a response, the tag may be configured to always perform the “Tag Not-Matching” action, as shown in FIG. 10, for the corresponding Action field value of the third Select command. For example, if the third Select command includes Target=100 and Action=000, the tag may always deassert the SL flag in response to receiving the third Select command. Select commands with nonmatching parameters may be used to cause tags to always assert, deassert, negate, or otherwise modify the value of a flag.

[0109] In some examples described herein, one or more of the flags may be assigned or mapped to memory locations that may not actually exist in the nonvolatile memory of the tag. A flag may be mapped to one or more different memory locations. The memory locations to which flags are mapped may or may not be contiguous.

[0110] When one or more flags aremapped to nonvolatile memory locations, the mapped flag(s) can be accessed using the Select command’s MemBank, Pointer, Length, and Mask fields, even if those locations do not actually exist in the nonvolatile memory. The Select command can then cause a potentially different flag specified in the Target field to change its state or value, as indicated in Table 1000, based on the value(s) of the mapped flag(s). For example, if the S0 flag is mapped to a certain memory location, a Select command may cause other flags to Change values based on the S0 flag. In this example, a Select command may be used to cause the SL flag of a tag to be asserted if the S0 flag is unassorted. More specifically, the Select command cam specify the memory location drat tire S0 flag is mapped to using the MemBank, Pointer, and Length fields, specify the condition that the S0 flag is unasserted using the Mask field (e.g., Mask=0), and cause the SL flag to be modified using the Target and Action fields (e.g., Target=100 and Action=001).

[0111] Subsequently, a reader can send a Gen2 Query command that instructs only tags with asserted SL flag values (via SeH I), which corresponds to tags with unassorted S0 flags, to participate in inventorying. Importantly, the Query command can then perform the inventorying with any of the four session flags S0, SI, S2, or S3.

[0112] Volatile flags or memory elements may be used to implement these flags. A volatile flag or memory component loses its stored value oyer some relatively short time duration when unpowered or when power is lost this differs from nonvolatile memories that are designed to store mid retain values even after power is lost.

[0113] FIG. 11 is a table 1100 illustrating the persistence times of various flags as specified in the Gen2 Protocol. Table 1 100 lists inventoried or “session” flags associated with four different inventorying sessions S0, S 1 , S2, and S3, as well as the “Selected” or SL flag. The flags may be implemented as volatile flags, for example, using volatile memory elements. Table 1100 lists the Genl protocol-required persistence times for these flags when the tag is powered (“energized”) and unpowered (“not energized”). A flag’s persistence time is the time duration during which it holds an “asserted” “B”, or “I” value. Most of the flags listed in table 1100 are required to persist (i.e., hold an “asserted", “B”, or “1” value) indefinitely when a tag is powered, however, the SI flag may decay while the tag is powered. Most of the flags listed in table 1100 (e.g., the SI, S2, S3, and SL flags) are required to persist for some finite time when the tag is unpowered when operating within a nominal temperature range. These flags that persist for a short time duration (e.g., lower than 2, 5, or 10 seconds, or lower titan a few minutes) after the RFID IC loses power are referred to as semi-persistent flags.

[0114] As described above, one or more of the flags may be assigned or “mapped" to one or more nonvolatile memory locations, whether or not those locations actually exist in the nonvolatile memory. This allows the session flags to be accessed using, for example, the Select or Read commands of the Gen2 Protocol. It should be noted that the session flags are not actually implemented as nonvolatile memory. Rather, when an RFID reader attempts to access data in a memory location “mapped” to a flag, the tag will refer to the current state or value of the mapped flag. For example, » memory location mapped to a certain session flag will appear to hold a “0" if the flag is unasserted and a " I " if the flag is asserted. In some examples, a Write command of the Gen2 Protocol may be able to change the value of any memory mapped flag.

[0115] FIG. 12 illustrates fields 1200 of a Query command according to the Gen2 Protocol.

[0116] A reader may use the Gen2 Query command to initiate an inventory round. In particular, the Query command specifies that tags meeting the criteria set forth in the Sei. Session, and Target fields participate in the inventory round. The Sei field value indicates whether all tags (e.g., SeI=00 or Sel=01), only tags with unasserted SL flags (e.g., Sel=10), or only tags with asserted SL flags (e.g., SeM 1) should participate in the inventory round. The Session field indicates which one of four inventoried flags to use in the inventory round. The Target field indicates which state or value the inventoried flag specified in the Session field should be in for a tag to participate in the inventory round. For example, field values of Session=00 and Target=A result in the reader causing tags whose inventoried flag S0 is “A” to participate in the inventory round.

[0117] Note dial while a Gen2 Query command can specify tag participation in an inventory round based on the values of a tag's SL flag and / or one inventoried flag, the Query command cannot specify tag participation based on two or more inventoried flags. Mapping one or more flags to memory locations, as described herein, allows a reader to effectively convert those mapped flags to the SL flag using a Gen2 Select command, thereby enabling a subsequent Gen2 Query command to effectively specify tag participation based on at least one mapped flag and another flag.

[0118] If inventorying can be done based on the values of multiple flags, then one “quieting” flag can be used to track whether a tag should be quiet, as described above, while another, different “inventorying” flag can be used to track the actual inventorying process.

[0119] In this approach, RFID readers first identify tags that should be quiet and set their “quieting” session flags to asserted values. Then, an RFID reader may issue a Select command targeting tags that have not been quieted (via the MemBank / Pointer / Length / Mask fields in the Select command) for a subsequent inventorying procedure. For example, the Select command may cause tags that have not been quieted to assert their SL flags. Then, the RFID reader may inventory tags with asserted SL flags using the “inventorying” session flag, which is different from the “quieting” session flag.

[0120] to an alternate approach, an RFID system may use the SL flag as the “quieting” flag. In this approach, tags to be quieted have their SL flags set to “0” (for example), using a first Select command targeting the SL flag. A second Select command targeting an “inventorying” session flag is then used to set the “inventorying” session flags of all tegs, even quieted tags, to “0” (for example). A subsequent inventorying command then initiates an inventorying procedure involving all tags with “inventorying” session flags at “0” but SL flags at “1 ”. in this way, the quieted togs with SL flags set to “0” will not participate in the inventorying procedure.

[0121] In the above two examples, tags to be quieted have quieting flags set to a “quieted value”, to the first example, the quieting session flag causes the teg to become quiet by asserting the quieting flag (e.g, the quieted value is an asserted value of “B” or “1”). In the second example, the SL flag causes the teg to become quiet by unasserting the SL flag (e.g., the quieted value is an unasserted value of “A” or “0*’); Different implementations may use different conventions for “quieted values”. A flag may also have a “non-quieted value”, which may be the opposite of the “quieted value”.

[0122] Tags to be quieted may be selected using any suitable method or criteria, to one example, the most responsive tags may be selected to be quieted because once they have been inventoried, they may tend to clutter up subsequent inventorying procedures the most. A tag’s responsiveness is based on how often it responds or participates in inventorying and may be related to the tag’s sensitivity - a tag with high sensitivity (i.e., can hear relatively low-power commands) tends to be more responsive than a tag with lower sensitivity. Accordingly, selecting tegs that are the most responsive may be accomplished by either (a) keeping a list of those tags, or (b) using a low-power selection command with the assumption that only tags with relatively high sensitivities will hear the command The selected tags can then be quieted as described above. In other situations, other tags may also be quieted. For example, tags that are not of interest, such as tags associated with stationary items, a facility, and / or tegs associated with items that have been processed (e.g., items loaded onto trucks, as described below) may be quieted.

[0123] to some situations, certain quieted tags may need to be unquieted, for example due to unintentional quieting or a change in the status of the tag or the item associatedwith the tag. If the specific tags that should be unquieted are known, then those tags can be selected (e.g., via Select commands) and unquieted. In some situations, those tags may not be known, and other methods can be used to unquiet them.

[0124] FIG. 13 illustrates an example implementation environment for quieting RFID tags using memory-mapped flags, according to embodiments.

[0125] Diagram 1300 shows a track 1302 with an inside antenna 1304 having a first range or field-of-view (FOV) and an outside antenna 1306 having a second range or FOV for an RFID reader system integrated into the truck 1302. The RFID reader system may inventory and perform other actions on RFID tags attached to items (e.g., items in truck 1312 and items outside track 1314) using the inside and outside antennas.

[0126] Consider a situation where tagged items (e.g., delivery packages) are being loaded onto and unloaded from the track 1302, depicted in diagram 1300. Truck 1302 may have one or more readers coupled to the inside antenna 1304 for inventorying tags within the track 1302 mid to the outside antenna 1306 for inventorying tags outside the truck 1302. Ideally, tags within track 1302 should have been already inventoried and quieted, while tags outside truck 1302 should be unquieted so that the tags can be (a) inventoried if they are to be loaded into the truck or (b) inventoried if they are to be moved elsewhere (e.g., for loading onto a different track),

[0127] However, one or more tags outside truck 1302 may be quieted, either unintentionally or because they are being moved outof the truck. These tags are visible from (i.e., readable by a reader coupled to) the outside antenna 1306. Thus, a simple solution may be to unquiet all tags visible from the outside antenna 1306. Unfortunately, some tags within truck 1302 may also be visible from the outside antenna 1306 (due to the nature ofRF wave propagation - as shown in FIG. 13, the range of tags '‘visible to outside antenna” may partially overlap with the range of tags “visible to inside antenna”). So, this simple solution may also cause those tags to be unquieted, which may be undesirable.

[0128] Another solution may be to differentiate tags that are visible from both the inside antenna 1304 and the outside antenna 1306 from tags that are only visible from the outside antenna 1306. Then, tags in the latter group may be unquieted without inadvertently unquieting tags within track 1302. This differentiation may beaccomplished by using another memory-mapped session flag, referred to as a “visible” flag, to track whether a tag is visible from the inside antenna 1304. Specifically, a reader may first cause tags that are visible from the inside antenna 1304 to asset their “visible” flags. Then a raider may cause only quieted tags visible from the outside antenna 1306 but having unasserted “visible” flags (indicating they are not visible from the inside antenna 1304) to unquiet themselves. This may unquiet only the quieted tags visible from the outside antenna 1306 but not visible from the inside antenna 1304. It should be noted that selecting quieted tags with unasserted “visible” flags involves selecting based on the values of two separate session flags (the “quiet” flag and the “visible” flag). If these different flags are mapped to tag nonvolatile memory locations, then a single Gen2 Select command may specify the values of multiple such memory-mapped flags at the same time, via the Length and Mask fields of the Select command.

[0129] In some situations, a reader may then cause the tags visible from the outside antenna 1306 to deassert their “visible” flags. Subsequently, a reader may then cause tags visible from the inside antenna 1304 to again assert their “visible” flags. This back-and-forth approach may help ensure that tags that move inside or outside have a chance to update their “visible” flags.

[0130] FIG. 14 is a flow diagram of a method 1400 for an RFID tag to access both a first volatile flag and a second volatile flag, according to embodiments. The tag may have a nonvolatile memory, a first volatile flag, and a second volatile flag. The first volatile flag may have or be associated with a first flag Identifier (e.g., an “S0 inventoried flag” or “S0 flag”) and be mapped to a first nonvolatile memory location. Similarly, the second volatile flag may have a second flag identifier (e.g„ an “S2 inventoried flag” or “S2 flag”) and be mapped to a second nonvolatile memory location. An RFID reader may request access to the first volatile flag and / or the, second volatile flag of tire tag using an inventorying command, such as a Query command of the Gen2 Protocol, a selection command, such as a Select command of the Gen2 Protocol, or any other command that specifies flags and / or memory locations to access.

[0131] The method 1400 may begin with the RFID reader transmitting a first command to the tag. An example of the first command can include a command that has fields that can be used to specify a memory location and a desired value for thememory content at the memory location, such as a Select command (e.g., via the MemBank, Pointer, Length, and Mask fields). The first command may request access to the first volatile flag and the second volatile flag by specifying the first nonvolatile memory location. For example, if the first and second volatile flags are mapped to first and second contiguous nonvolatile memory locations, the first command can request access to both flags using the MemBank field to select the appropriate memory bank, the Pointer field to point to the first nonvolatile memory location, and the Length field to indicate a length of two. In some embodiments, the first and second nonvolatile memory locations may not actually exist in the nonvolatile memory of the tag. The first command may also include a mask value having first and second bits that correspond to the first and second volatile flags. For example, the reader may use a Mask field of the Select command to indicate the desired first and second flag states (e.g., Mask=00 would indicate that the RFID reader is looking for tags that have unasserted first and second volatile memory flags). The first command may also specify, using the Target field, a target flag to perform an action on (e.g., using the Action field of a Select command).

[0132] At block 1402, the tag may receive the first command. The first command may have a pointer value that specifies the first nonvolatile memory location and a mask value having first and second bits. The first bit may correspond to the first volatile flag and the second bit may correspond to the second volatile flag.

[0133] At Hock 1404, in response to receiving the first command, the tag may allow access to both the first and second volatile flags. Embodiments may “allow access” to a volatile flag by causing the RFID 1C to retrieve a value of the volatile flag and to then compare the retrieved value of the volatile flag with a desired flag value that is received in a command. For example, upon receiving the first command, the tag may determine that the first command’s MemBank, Pointer, and Length field values correspond to the first and second volatile flags, and accordingly retrieve or refer to the current values of the first and second volatile flags. The tag may then compare the values of the first and second volatile flags to the first and second bit values of the mask value.

[0134] The first command may also specify a target flag (e.g., using a Target field of a Select command) for an action that is based on the comparison of the state of the first and second volatile flags to the firstand second bit values of the mask value (e.g.,using the Action field as described by FIG. 10). The target flag may be the first or second volatile flags, or may be a third volatile flag. The action may indicate a first action for the tag to perform if the first and second bit values match the value of the first and second volatile flags (e.g., the “Tag Matching” action of one action in the Table 1000). The action may also indicate a second action for the tag toperform if the first and second bit values do not match the value of the first and second volatile flags (e.g., the ‘Tag Not-Matching” action of the same action in the Table 1000). In some examples, the first command may be something other than a selection command that causes a receiving tag to perform actions based on whether its volatile flag values correspond to those specified in the first command. In other examples, the first command may enable Boolean operations to be performed on the values of two or more volatile flags and one or more actions to be taken based on the outputs of those Boolean operations.[0135J Memory-mapped flags allow the RFID reader to access multiple flags with the first command. If only one flag is of interest (e.g.» as in a simple inventorying procedure), the RFID reader may instead transmit an inventory ing command to access one of the volatile flags. For example, the inventorying command may specify one of the first and second flag identifiers to access the corresponding volatile flag.

[0136] At block 1406, the tag may receive the inventorying command, the inventorying command may specify the first flag identifier, which corresponds to the first volatile flag, or it may specify the second flag identifier; which corresponds to the second volatile flag. For example, the inventorying command may be a Query command, and it may specify the first flag identifier using the Session field. The inventorying command may not be able to specify both the first volatile flag and the second volatile flag in a single command (e.g., a Query command may specify values for both a selected flag and one session flag, but it cannot specify values for two session flags).

[0137] At block 1408, in response to receiving the inventorying command, the tag may access the volatile flag corresponding to the flag identifier specified by the inventorying command. The inventorying command may cause the tag to directly access the corresponding volatile flag. For example, if the inventorying command is a Query command, the tag may respond to the inventorying command as specified by the Gen2 Protocol.

[0138] The method 1400 allows for a tag to access multiple memory-mapped flags using, for example, a selection command, or a single flag using an inventorying command. FIG. 15 provides a detailed view on an RFID tag providing access to single memory-mapped volatile flag,

[0139] FIG. 15 is a flow diagram of a method 1500 for an RFID tag to access a first volatile flag, according to embodiments. Similar to the above FIG. 14, the tag may have a nonvolatile memory, and the first volatile flag may have a first flag identifier and be mapped to a first nonvolatile memory location that may not actually exist in the tag’s nonvolatile memory. An RFID reader may use an inventorying command to cause the tag to participate in an inventory round, tracked using tire first volatile flag.

[0140] At block 1502, the tag may receive the inventorying command.

[0141] At block 1504, after receiving the inventorying command, the tag may determine that the inventorying command specifies a first volatile flag using a first flag identifier and includes a first desired flag value. For example, a Gen2 Query command may include a first flag identifier specifying the first volatile flag using the Session field and the first desired flag value may be included in the Target field of the Query command. This Query command may initiate an inventory round involving tags whose first volatile flags have the first desired flag value.

[0142] At block 1506, in response to the determination, the tag may compare the first volatile flag to the first desired flag value. The tag may access the first volatile flag directly arid compare the first volatile flag (e.g., the state or value of the first volatile flag) to the first desired flag value. For example, the first desired flag value may be “A” and the first volatile flag may be either in the “A” or “B” State. The tag may, if the first volatile flag is in the desired “A” state, participate in the inventory round associated with the inventorying command. Otherwise, if the first volatile flag is in the “B” state, the tag may not participate in the inventory round.

[0143] At another time, the RFID reader may transnit a second command to the tag. The second command may be a command that has fields that can be used to specify a memory location and a desired value for the memory content at the memory location, such as a selection command like the Select command of the Gen2 protocol.

[0144] At block 1508, the teg may receive the second command.

[0145] At block 1510, after receiving the second command, the tag may determine . that the second command specifies the first volatile flag using the first nonvolatile memory location (e.g., the memory location that the first volatile flag is mapped to) and includes a second desired flag value. As described above, the memory-mapped first volatile flag may not actually be implemented in the nonvolatile memory. Rather, the first nonvolatile memory location points to the first volatile flag and the tag will refer to the current state or value of the first volatile flag, which may be implemented by volatile memory or flags that are separate from the nonvolatile memory.

[0146] At block 1512, in response to the determination, tire tag may compare the value of the first volatile flag to the second desired flag value. For example, the second desired flag value may be included in the Mask field of a Select command. The tag pray compare the bits of the Mask field to the value of the first volatile flag, and perform an action based on the comparison.

[0147] The methods 1400 and 1500 allow for RFID readers to specify RFID tags based on values of one or more flags. These methods can allow RFID readers to implement quieting flags, such as those described in FIG; 12.

[0148] FIG. 16 is a flow diagram of a method 1600 for inventorying RFID tags using a memory-mapped flag, according to embodiments. An RFID reader may use one session flag (e.g., either S0, SI, S2, or S3) or the selected flag (e.g., St) to use as a quieting flag. The quieting flag may be mapped to a tag nonvolatile memory location, similarly to the volatile flags described by FlGs. 15 and 16. The RFID reader may also determine the state of flags that corresponds to a quieted tag (e.g., a “1" session flag and a “0" SL flag may correspond to a quieted tag), or the “quieted value*, mentioned above. This may also implicitly determine the “non-quieted value'' for quieting flags. The RFID reader may first determine a first plurality of tags to become quiet, for example, based on the responsiveness of the tags.

[0149] At block 1602, an RFID reader may cause the first plurality of tags to become quiet by causing their quieting flags to have the quieted value. For example, the RFID reader may use a Select command to target the quieting flag and cause the quieting flag to have the quieted value. In one such example, the select command may be a nonmatching select command that points to a memory location that does not exist, such that the tag cannot match memory content (which does not exist) to the maskvalue, and thereby causes the tag to always perform a nonmatching action that sets the quieting flag to have a quieted value. In the example where a session flag is used as the quieting flag, the RFID reader may cause the session flag to be asserted. In the example where the selected flag is used as the quieting flag, the RFID reader may cause the selected flag to be unasserted, However, in other examples a quieting flag with a quieted value may correspond to an unasserted session flag or an asserted selected flag.

[0150] At block 1604, the RFID reader may send a first command specifying a nonquieted value for a tag nonvolatile memory location mapped to the quieting flag to select tags not in the first plurality of the RFID tags. In the example where a session flag is used as the quieting flag, the RFID reader may send another Select command targeting tags that have not been quieted and cause them to set their selected flag to a selected value (assorted or deasserted) for a subsequent inventorying process. In the example where the selected flag is used as the quieting flag, the RFID reader may send another Select command targeting all tags and causing an inventorying session flag to be set to an inventorying value (unasserted or asserted, depending on the inventorying).

[0151] At block 1606, after selecting the tags, the RFID reader may inventory the selected tags using a session flag different from the quieting flag. In the example where a session flag is used as foequieting flag, the RFID reader may inventory tags (e.g., using a Query command) that have an SL flag at the selected value but have quieting flags at the quieted value using an inventorying session flag that is different than the quieting flag. In the example where the selected flag is used as the quieting flag, the RFID reader may inventory tags, again using a Query command, that have an inventory ing session flag at the inventorying value but an SL flag at the quieted value.

[0152] FIG- 17 is flow diagram of a method 1700 for inventorying RFID tags using memory-mapped flags, according to embodiments. The method 1700 may be performed by an RFID reader system, such as dial described by FIG. 13. The RFID reader system may include a first reader antenna having a first range or FOV and a second reader antenna having a second range or FOV that is partially overlapping wifo the first range. Similar to the method 1600, the RFID reader system may use one session flag (e.g„ either S0, SI, S2, or S3) or the selected flag (e.g., SL) to use as a quieting flag. The RFID reader system may then use a different flag as a visibilityflag. The quieting flag and the visibility flags may be both memory-mapped to nonvolatile memory locations, similarly to the method 1400. In the examples described, the SI flag is used for inventorying, the S2 flag is used for quieting, and the S3 flag is used for tag visibility to the inside antenna.

[0153] At block 1702, tire RFID reader system may inventory non-quieted tags using the first reader antenna. For example, the RFID reader system can use a Select command to select all tags with quieting (S2) flags set to a non-quieted value (e.g., unasserted) and then subsequently use a Query command to inventory all selected tags with inventorying (SI) flags set to an inventorying value (e.g., unasserted).

[0154] At block 1704, after inventorying all non-quieted tags, the RFID reader system may use the first reader antenna to cause all tags to indicate that they are visible to the first reader antenna. For example, a Select command with nonmatching values (e.g., MemBank, Pointer, and / or Length field values that point to a memory location that does not exist in the memory of the tags) may cause all tags to set their visibility (S3) flags to a visible value (e.g., asserted).

[0155] At block 1706, the RFID reader system may inventory non-quieted tags using the second reader antenna. Similar to block 1702, the RFID reader system may use a Select command to select all non-quieted tags and then subsequently use a Query command to inventory all selected tags with inventorying (SI) flags set to the inventory ing value (e.g„ unasserted).

[0156] At block 1708, after inventorying the non-quieted tags, the RFID reader system may first cause quieted tags that indicate they are not visible to the first reader antenna to become unquieted. In one example, because both the quieting (S2) flag and the visibility (S3) flag are memory-mapped, the RFID reader system may use a single Select command with a Mask value indicating an asserted quieting (S2) flag and an unassorted visibility (S3) flag (e.g., Mask=(S2=1, S3=0)).

[0157] At block 1710, after causing all quieted tags indicating that they are not visible to become unquieted, the RFlD reader system may cause all RFID tags to indicate that they are not visible to the first reader antenna. For example, the RFID reader system may use a Select command with nonmatching values and targeting the visibility flag to cause the visibility flag to be set to a not- visible value (e.g., unasserted).

[0158] The steps described in the methods 1400, 1500, 1600 and 1700 are for illustrative purposes only. These steps may be implemented using additional or fewer steps and in different orders using the principles described herein.

[0159] According to some examples, a method for an RFID IC to access a first volatile flag having a first flag identifier and mapped to a first nonvolatile memory location and a second volatile flag having a second flag identifier and mapped to a second nonvolatile memory location may include receiving, via a transceiver of the RFID IC, a first command. The first command may have a pointer value specifying the first nonvolatile memory location and a mask value having a first bit and a second bit The first bit may correspond to the first volatile flag and the second bit may correspond to the second volatile flag. In response to receiving the first command, the RFID IC may access both the first and second volatile flags. The method may also include receiving, via the transceiver, an inventorying command specifying one of the first and second flag identifiers. In response to receiving the inventorying command, the RFID IC may access the volatile flag that corresponds to the flag identifier that is specified by the inventorying command.

[0160] According to other examples, a position of the second bit in the mask value may correspond to the second nonvolatile memory location. The second nonvolatile memory location may be located contiguously after the first nonvolatile memory location. The first and second nonvolatile memory locations may be separate by at least one bit and the mask value may have a length greater than the at least one bit between the first nonvolatile memory location and the second nonvolatile memory location. The first and second volatile flags may be semi-persistent flags that are designed to persist for a short time duration after the RFID IC loses power. The first volatile flag may be an inventoried flag of a first session or a selected flag and the second volatile flag may be an inventoried flag of a second session different than the first session, according to the Gen2 Protocol. The first command may indicate a first action and the method may further include performing the first action only if both a value of the first bit is equal to a value of the first volatile flag and a value of the second bit is equal to a value of the second volatile flag. The first command may be a selection command and the first action may be performed on a third volatile flag of the RFID IC. Accessing a volatile flag may comprise retrieving a value of the volatile flag and comparing the retrieved value with a desired value received in a command.

[0161] According to further examples, a method for an RFID 1C to access a first volatile flag having a first flag identifier and mapped to a first nonvolatile memory location. The method may include the RFID IC receiving an inventorying command. The RFID IC may determine that the inventorying command specifies the first volatile flag using a first flag identifier and includes a first desired flag value. The RFID IC may then compare the first volatile flag to the first desired flag value. The method my also include the RFID IC receiving a second command. The RFID IC may determine that the second command specifies the first volatile flag using the first nonvolatile memory location and includes a second desired flag value. The RFID IC may then compare the first volatile flag to the second desired flag value.

[0162] According to yet other examples, an RFID IC may include a nonvolatile memory. The RFID IC may also have a first volatile flag having a first flag identifier and mapped to a first nonvolatile memory location. The RFID IC may also have a second volatile flag having a second flag identifier and mapped to a second nonvolatile memory location. The RFID IC may further include a transceiver that is configured to receive and respond to commands. The RFID IC may also include a processing block that is coupled to the memory, the first volatile flag, the second volatile flag, and the transceiver. The processing block can be configured to perform methods for the RFID IC to access the first volatile flag and the second volatile flag. For example, the processing block may be configured to perform the methods 1400 and 1500 as described above. The processing block may further be configured to respond to commands received by RFID readers, such as those commands received by RFID tag ICs in the methods 1600 and 1700.

[0163] According to other examples, a method for an RFID reader to inventory RFID tags that are configured with memory-mapped flags includes the RFID reader causing a first plurality of tags to become quiet by modifying a memory-mapped quieting flag to have a quieted value. The method may further include the RFID reader sending a first command specifying a non-quieted value for a tag nonvolatile memory location that is mapped to the quieting flag to select tags that are notin the first plurality of tags, the RFID reader may then inventory the selected RFID tags using a session flag that is different from the quieting flag.

[0164] According to yet other examples, a method for an RFID reader system including a first reader antenna and a second reader antenna to selectively unquietRFID tags that are configured witii memory-mapped flags includes using the first reader antenna to: inventory non-quieted RFID tags, and cause RFID tags to indicate that they are visible to the first reader antenna. The method may also include the RFID reader system using the second reader antenna to: inventory non-quieted RFID tags; cause quieted tags hot visible to the first reader antenna to become quieted and then cause RFID tags to indicate that they are not visible to the first reader antenna. The first reader antenna and the second reader antenna may have overlapping ranges.

[0165] As mentioned previously, embodiments are directed to tag inventorying based on memory-mapped flags. Embodiments additionally include programs, and methods of operation of the prognuns. A program is generally defined as a group of steps or operations leading to a desired result, due to the nature of the elements in the steps and their sequence. A program is usually advantageously implemented as a sequence of steps or operations for a processor, but may be implemented in other processing elements such aS FPGAs, DSPs, or other devices as described above.

[0166] Performing the steps, instructions, or operations of a program requires manipulating physical quantities. Usually, though not necessarily, these quantities may be transferred, combined, compared, and otherwise manipulated or processed according to the steps or instructions, and they may also be stored in a computer- readable medium. These quantities include, tor example, electrical magnetic, and electromagnetic charges or particles, states of matter, and in more general case can include the states of any physical devices or elements. It is convenient at times, principally for reasons of common usage, to refer to information represented by the states of these quantities as bits, data bits, samples, values, symbols, characters, terms, numbers, or the like. It should be home in mind, however, that all of these and similar terms are associated with the appropriate physical quantities, and that these terms are merely convenient labels applied to these physical quantities, individually or in groups.

[0167] Embodiments furthermore include storage media. Such media, individually or in combination with others, have stored thereon instructions, data, keys, signatures, and other data of a program made according to the embodiments. A storage medium according to the embodiments is a computer-readable medium, such as a memoiy, and is read by a processor of the type mentioned above. If a memoiy, it can be implemented in any of the ways and using any of the technologies described above.

[0168] Even though it is said that the program may be stored in a computer-readable medium, it should be clear to a person skil led in the art that it need not be a single memory, or even a single machine. Various portions, modules or features of it may reside in separate memories, or even separate machines. The separate machines may be connected directly . or through a network such as a local access network ( LAN ) or a global network such as the Internet.

[0169] O ften, for the sake of convenience on ly , it is desirable to implement and describe a program as software. The software can be unitary or thought of in terms of various interconnected distinct software modules.

[0170] The foregoing detailed description has set forth various embodiments of the devices and / or processes via the use of block diagrams and or examples. Insofar as such block diagrams and / or examples contain one or more functions and / or aspects, it will be understood by those vv ithin the an that each function and or aspect w ilhin such block diagrams or examples may be implemented individually:and / or collectively, by a wide range of hardware, softw are. firmware, or virtually any combination Hereof. those sk lied in the art w ill recognize that some aspects of the RF I D) embodiments disclosed herein, in w hole or in part, mas be equivalently implemented employing integrated circuits, as one or more computer programs running on one or more computers (e.g.. as one or more programs running on one or more computer systems), as one or more programs running on one or more processors (e g. as one or more programs running on one or more microprocessors ), as f irmware-, or as v irtually any combination thereof, and that designing the circuitry and-or w riting the code for the software and / or firmware would be well within the skill of one of skill in the art in light of this disclosure.

[0171] The present disclosure is not to be limited in terms of the particular embodiments -described in this application, which are intended as illustrations of v arious aspects. Many modi fications and variations can be made w ithout departing from its Spirit and scope, as will be apparent to those skilled in the art. Functionally equivalent methods and apparatuses within the scope of the disclosure, in addition to those enumerated herein, will be apparent to those skilled in the art from the foregoing descriptions. Such modifications and v ariations arc intended to tall w ithin the scope of the appended claims. The present disclosure is to be limited only by the terms of the appended claims, along with the full scope of equivalents to which suchclaims are entitled. It is to be understood that this disclosure is not limited to particular methods, configurations, antennas, transmission lines, and the like, which can, of course, vary. It is also to be understood that the terminology used herein is for the purpose of describing particular embodiments only, and is not intended to be limiting.

[0172] With respect to the use of substantially any plural and / or singular terms herein, those having skill in the art can translate from the plural to the singular and / or from the singular to the plural as is appropriate to the context and / or application. The various singular / plural permutations may be expressly set forth herein for sake of clarity.

[0173] ft will be understood by those within the art that, in general, termsused herein, , and especially in the appended claims (e.g., bodies of the appended claims) are generally intended as “open” terms (e.g., the term “including” should be interpreted as “including but not limited to,” the term “having” should be interpreted as “having at least,” the term “includes” should be interpreted as “includes but is not limited to ” etc.), ft will be further understood by those within the art that if a specific number of ah introduced claim recitation is intended, such an intent will be explicitly recited in toe claim, and in toe absence of such recitation no such intent is present Tor example, as an aid to understanding, toe following appended claims may contain usage of the introductory phrases "at least one* and "one or more" to introduce claim recitations. However, the use of such phrases should not be construed to imply that the introduction of a claim recitation by toe indefinite articles "a" or "an" limits any particular claim containing such introduced claim recitation to embodiments containing only one such recitation, even when the same claim includes the introductory phrases "one or more" or "at least one" and indefinite articles such as "a" or "an" (e.g., “a” and / or “an” should be interpreted to mean “at least one” or “one or more"); the same holds true for the use of definite articles used to introduce claim recitations. In addition, even if a specific number of an introduced claim recitation is explicitly recited, those skilled in the art will recognize that such recitation should be interpreted to mean at least the recited number (e.g., the bare recitation of "two recitations," without other modifiers, means at least two recitations, or two or more recitations).

[0174] Furthermore, in those instances where a convention analogous to “at least one of A, B, and C, etc.” is used, in general such a construction is intended in the sense one having skill in the art would understand the convention (eg., “a system having at least one of A, B, and C” would include but not be limited to systems that have A alone, B alone, C alone, A and B together, A and C together, B and C together, and / or A, B, and C together, etc.). It will be further understood by those within the art that virtually any disjunctive word and / or phrase presenting two or more alternative terms, whether in the description, claims, or drawings, should be understood to contemplate the possibilities of including one of the terms, either of the terms, or both terms. For example, the phrase “A or B“ will be understood to include the possibilities of “A" or “B” or “A and B.”

[0175] As will be understood by one skilled in the art, for any and all purposes, such as. in terms of providing a written description, all ranges disclosed herein also encompass any and all possible subranges and combinations of subranges thereof. Any listed range can be easily recognized as sufficiently describing arid enabling the same range being broken down into at least equal halves, thirds, quarters, fifths, tenths, etc. As a non-limiting example, each range discussed herein can be readily broken down into a lower third, middle third and upper third, etc. As will also be understood by one skilled in the art all language such as “up to,” “at least,” “greater than,” "less than,” and the like include the number recited and refer to ranges which can be subsequently broken down into subranges as discussed above. Finally, as will be understood by one skilled in the art, a range includes each individual member. Thus, for example, a group having 1-3 cells refers to groups having 1, 2, or 3 cells. Similarly, a group having 1-5 cells refers to groups having 1, 2, 3, 4, or 5 cells, and so forth;

Claims

CLAIMSWE CLAIM:

1. A method for a radio frequency identification (RFID) integrated circuit (IC) to access a first volatile flag having a first flag identifier and mapped to a first nonvolatile memory location and a second volatile flag having a second flag identifier and mapped to a second nonvolatile memory location, the method comprising: receiving, via a transceiver of the RFID JC, a first command having a pointer value specifying the first nonvolatile memory location and a mask value having a first bit and a second bit, wherein the first bit corresponds to the first volatile flag and the second bit corresponds to the second volatile flag; in response to receiving the first command, accessing both the first and second volatile flags; receiving, via the transceiver, an inventorying command specifying one of the first and second flag identifiers; and in response to receiving the inventorying command, accessing one of the first and second volatile flags corresponding to one of the first and second the flag identifiers specified by the inventorying command.2, The method of claim 1, wherein a position of the second bit in the mask value corresponds to the second nonvolatile memory location.

3. The method of claim 1, wherein the second nonvolatile memory location is located contiguously after the first nonvolatile memory location.

4. The method of claim 1, wherein: the first and second nonvolatile memory locations are separated by at least one bit, and the mask value has a length greater than tire at least one bit between the first nonvolatile memory location and the second nonvolatile memory location.

5. The method of claim 1, wherein toe first and second volatile flags are semi- persistent flags designed to persist for a short tune duration after the RFID 1C loses power.

6. The method of claim 1, wherein: the first volatile flag is one of: an inventoried flag of a first session according to the Gen2 Protocol, and a selected flag according to the Gen2 Protocol; and the second volatile flag is an inventoried flag of a second session different than the first session, according to the Gen2 Protocol.

7. The method of claim 1, wherein the first command indicates a first action and the method further comprises: performing toe first action only if both a value of the first bit is equal to a value of the first volatile flag and a value of the second bit is equal to a value of the second volatile flag.

8. The method of claim 7, wherein the first command is a selection command and toe first action is performed on a third volatile flag of toe RFID 1C.

9. The method of claim I , wherein accessing a volatile flag comprises retrieving a value of the volatile flag and comparing the retrieved value with a desired value received in a command.

10. A radio frequency identification (RFID) integrated circuit (1C) comprising: a nonvolatile memory; a first volatile flag having a first flag identifier and mapped to a first nonvolatile memory location; a second volatile flag having a second flag identifier and mapped to a second nonvolatile memory location; a transceiver Configured to receive and respond to commands; anda processing block coupled to the nonvolatile memory, the first volatile flag, the second volatile flag, and the transceiver, wherein the processing block is configured to perform the method of one of the claims 1 - 9.

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