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EPCglobal Training SuiteEPCglobal Training SuiteEPCglobal Training SuiteEPCglobal Training Suite

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IntroductionIntroduction

Tag Protocol - UHF Class 1 Gen 2• Ultra High Frequency (UHF)• Generation 2 (Generation 1 is deprecated)• Class 1

Classification Active/Passive Description

Class 1 Passive Write Once, Read Many Times

Class 2 Passive Read / Write

Class 3 Semi-Passive Read / Write with battery power to enhance range

Class 4 Active Read / Write active transmitter

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Tag MemoryTag Memory

Four Memory Banks• Reserved Bank (00)

• Uses for Tag operation control

• EPC Bank (01)• Uses for storing EPC

• TID Bank (10)• Uses for storing unique Tag Identification (TID)

• User Bank (11)• Uses for storing user defined fields

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Tag MemoryTag Memory

Reserved Memory• [00-1F] Kill Password

• [20-3F] Access Password

EPC Bank• [00-0F] Cyclic-Redundancy Check

• [10-1F] Protocol Control

• [20-xx] Electronic Product Code

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Tag MemoryTag Memory

TID Bank• [00-xx] Tag Identification

User Bank• [00-07] Data Storage Format Identifier (DSFID)

• [08-xx] User Defined Fields

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Tag State DiagramTag State Diagram

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Reader CommandsReader Commands

Select Commands• Selects Tag groups to communicating

Inventory Commands• Collecting EPC of Tags in reading range

Access Commands• Access data of specified Tag

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Reader CommandsReader Commands

Select Commands• Selects Tag groups to

communicating

Commands• Select

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Reader CommandsReader Commands

Select Commands• Select can assert or deassert a Tag’s SL flag, or it can set a

Tag’s inventoried flag to either A or B in any one of the four sessions.

The conditions to check a tag is matching or non-matching

Tag’s flags

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Reader CommandsReader Commands

Inventory Commands• Collecting EPC of Tags in

reading range

Commands• Query, QueryAdjust,

QueryRep, ACK, NAK

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Reader CommandsReader Commands

Query• Query initiates and specifies an inventory round.

Choose a group of tags

Tag will pick a random value (slot) in the range2Q− 1If Tag’s slot = 0, the Tag reply RN16.

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Reader CommandsReader Commands

QueryAdjust• QueryAdjust adjusts Q without changing any other round

parameters.Tag will pick a NEW random value

in the range2Q− 1

If Tag’s slot = 0, the Tag reply RN16.

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Reader CommandsReader Commands

QueryRep• QueryRep instructs Tags to decrement their slot counters.• If slot = 0 after decrementing, it will backscatter an RN16 to

Interrogater.

If Tag’s slot = 0, the Tag reply RN16.

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Reader CommandsReader Commands

ACK• ACK echoes the Tag’s backscattered RN16.

Tag reply to a successful ACK command

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Reader CommandsReader Commands

NAK• Any Tag that receives a NAK shall return to the arbitrate state

without changing its inventoried flag (unless the Tag is in ready or killed).

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Reader CommandsReader Commands

Command Sequence (Inventory)Reader Tag1 Tag2 Tag3

Query (Q=1) Slot=0, Reply RN16 Slot=1 Slot=1

ACK (RN16(1)) Reply EPC

QueryRep Slot=0, Reply RN16 Slot=0, Reply RN16

QueryAdj(Q=2) 1 2

QueryRep Slot=0, Reply RN16 Slot=1

ACK(RN16(2)) ReplyEPC

QueryRep Slot=0, Reply RN16

ACK(RN16(3)) Reply EPC

QueryRep

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Reader CommandsReader Commands

Access CommandsAccess data of specified Tag

CommandsReq_RN, Read, Write, Kill, Lock, Access, BlockWrite, BlockErase

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Reader CommandsReader Commands

Access• Access Password (32 bits)• Using access password before accessing Tag data

Read• MemBank

• Select which Tag Memory Bank to be read• WordPtr

• Specify start reading point. A word is 16 bits• WordCount

• Specify how many words to be read

Write• MemBank

• Select which Tag Memory Bank to be write• WordPtr

• Specify start writing point. A word is 16 bits• Data

• The data to be written in MemBank. Writing a word (16 bits) at a time

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Reader CommandsReader Commands

Kill• Kill Password (32 bits)

Req_RN• Instructs a Tag to backscatter a new RN16.

Lock• Lock / Unlock / PermaLock

• Mask (10 bits) and Action (10 bits)

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Reader CommandsReader Commands

BlockWrite• MemBank

• Select which Tag Memory Bank to be written• WordPtr

• Specify start writing point• WordCount

• Specify how many words to be written• Data

• The data to be written in MemBank. Data length is (16 bits * WordCount)

BlockErase• MemBank

• Select which Tag Memory Bank to be erased• WordPtr

• Specify start erasing point• WordCount

• Specify how many words to be erased

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Collision ProblemCollision Problem

What is Collision?• Readers and Tags can not resolve noise signal into correct messages• The radio interference, the noise, is occurred when multiple radio signal

of the same frequency are raised at the same time

Reader Collision• Two or more Readers communication with the same Tag

Tag Collision• Two or more Tags communication with the same Reader

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Solutions of Collision ProblemSolutions of Collision Problem

Reader Collision• Time Division Multiple Access (TDMA)

• Readers send commands in different time slot

• Frequency Division Multiple Access (FDMA)• Readers send commands by different radio frequency

Tag Collision• Slotted Aloha

• Tags send messages in different time slot

• Tree Walk• The Tags have the number that Reader specified can response