How to select RFID UHF tag
UHF applications are doing more and more ,and how to design systems based on the practical application to achieve betteruse of results , in which the UHF (EPCClass1Gen2) electronic tag content iscrucial to understand , a lot of friends on the RFID tag know much , Kai Yuespecial order of things some information for your reference, wherediscrepancies welcome more correction .
Meet EPCClass1Gen2 ( referred G2) protocolV109 version of the electronic tag (Tag, abbreviated label ) and Reader (reader ) , you should have the following features.
Q1: KLTAG tag memory which is divided intoseveral zones ?
A: Tagmemory ( tag memory ) dividedReserved ( Reserved ), EPC ( electronic product code ), TID ( tagidentification number ) and User ( user ) four separate memory blocks (Bank).
Reserved Area : Storage KillPassword (inactivated password ) and AccessPassword ( access password ) .
EPC Area : Store EPC numbers.
TID District : Storage tag identificationnumber, each TID number should be unique.
User Area : store user -defined data.
There are also various blocks Lock ( Lock )status bit is also used in the storage properties of such a unit .
Q2: KLTAG label , which has several state ?
A: Yes, continuous wave (CW) exposure thatpower (Power-up) after the label can be in Ready ( ready ), Arbitrate ( cutting), Reply ( back order ), Acknowledged ( answer ), Open ( Open ), Secured ( protection), Killed ( inactivated ) seven kinds of states.
1, Ready state on the label is notinactivated power , they began the state , ready to respond to commands.
2, in the Arbitrate state , primarily Querycommands such as waiting for a response .
3 , in response to Query , enter the Replystate , further response ACK command can be sent back to EPC number.
4 , sent back EPC number, enterAcknowledged state , and further can respond Req_RN command.
5, AccessPassword not zero before they canenter the Open state , in which the read and write operations.
6 , it may enter Secured knownAccessPassword state , to read, write , lock and other operations.
7 , go to the Killed state label willremain unchanged and will never generate a modulated signal to activate the RFfield , thereby permanently disabled. Inactivated label should be maintained inall environments Killed state , the power to enter inactivated state.Irreversible inactivation of operation .
To make the label into a state generallyrequires proper sequencing of a combination method command , in turn, can onlybe when the label of each command in the appropriate state to be effective, thetag response command will go to other states.
Q3: Which commands are divided into severalcategories ?
A: From the command architecture andscalability perspective , divided into Mandatory ( mandatory ), Optional (optional ), Proprietary ( proprietary ) and Custom ( customized ) fourcategories.
From the use of functional point of view,is divided into labels Select ( Select ), Inventory ( inventory ) and Access (Access ) command categories.
In addition, orders for future expansion ofthe length of different coding aside for later use.
Q4: essential (Mandatory) command is what ?
A: Meets G2 protocol tags and readers , andshould support the necessary commands are eleven : Select ( Select ), Query (query ), QueryAdjust ( adjust query ), QueryRep ( repeated queries ), ACK (EPCreply ) , NAK ( steering cutting ), Req_RN ( random number request ), Read ( R), Write ( write ), Kill ( inactivated ), Lock ( lock ) .
Q5: Optional (Optional) command what ?
A: Meets G2 protocol tags and readers ,support can not support the optional command has three : Access ( Access ),BlockWrite ( block write ), BlockErase ( block erase ) .
Q6: Proprietary (Proprietary) command iswhat ?
A: proprietary command is generally usedfor manufacturing purposes , such as labels and other internal testing ,labeling manufactured after this command should be permanently disabled.
Q7: Custom (Custom) What are the command ?
A: Yes, the manufacturers themselves andopen to the user defined commands , such as the Philips company provides :BlockLock ( block lock ), ChangeEAS ( EAS change state ), EASAlarm (EAS alarm )and other commands (EAS electronic anti- theft system is a commodityElectronicArticleSurveillance abbreviation ) .
Q8: Select (Select) class command what ?
A: Only one : Select, is a must.
Tag has a variety of attributes , based onstandards and policies set by the user , using the Select command to changesome attributes and flags on artificial selection , or the delineation of aparticular tag group , you can only count on them to identify or accessoperation , so helps to reduce conflict and duplication identification,accelerate the recognition speed .
Q9: Inventory (Inventory) class commandwhat ?
A: There are five : Query, QueryAdjust,QueryRep, ACK, NAK, are essential.
1 , the label receipt of a valid Querycommand, meet set standards are selected each tag generates a random number (like dice ) , and a random number is zero for each label , will reverberate (RN16 temporary password sent back - a 16-bit random number ) , and transferredto the Reply state ; meet some conditions the label will change some of theproperties and flags , thus exiting the tag group , helps to reduce duplicateidentification .
2 , the label QueryAdjust receipt of avalid command, but the new labels to generate a random number ( like re- rollthe dice ) , the other with Query.
3 , the label receipt of a valid QueryRepcommand, only the label group in the original random number each label minusone , the other with Query.
4 , only one of the labels in order toreceive a valid ACK command ( using the RN16, or handle Handle - a temporaryidentity label represents the 16-bit random number. This is a securitymechanism ! ) , Received, sent back EPC zone content ?? EPC protocol most basicfunctions.
5 , the label after receipt of a valid NAKcommand , except in Ready, Killed by keeping the original state , the othercases are transferred to Arbitrate state.
Q10: Access (Access) type command what ?
A: There are five essential : Req_RN, Read,Write, Kill, Lock, and three optional : Access, BlockWrite, BlockErase.
1 , the label receipt of a valid Req_RN(withRN16orHandle) command, sent back handle or a new RN16, depending on thestate and different.
2 , the label receipt of a valid Read(withHandle) command, sends back an error type code, or required contents ofthe block and handle.
3 , the label receipt of a valid Write(withRN16 & Handle) command, sends back an error type code, or write backto handle success .
4 , label receipt of a valid Kill(withKillPassword, RN16 & Handle) command, sends back an error type code,or inactivation success back handle.
5 , the label receipt of a valid Lock(withHandle) command, sends back an error type code, or lock the handle back tosuccess .
6 , labels receipt of a valid Access(withAccessPassword, RN16 & Handle) command, sent back handle.
7 , labels receipt of a valid BlockWrite(withHandle) command, sends back an error type code, or block write back tohandle success .
8 , the label receipt of a valid BlockErase(withHandle) command, sends back an error type code, or block erase success backhandle.
Q11: The so-called conflict (collisions)how it is, how anti-collision ? What mechanisms G2 anti- conflict ?
A: When the above mentioned solution Q9 ,when there is more than zero, a random number sent back to different pins ofthe RN16 , they will appear at the receive antenna of the waveformsuperposition of different RN16 , also known conflicts (collisions) and thuscan not correctly decode . There are many anti- collision mechanismsuperimposed waveform distortion can be avoided , for example, managed to (midnight ) to make certain that only one label " speak" , followed bya single treatment, will be able to read and write more than one labelidentifying each of a label.
The three Q -prefix command reflects the G2anti- collision mechanism : random number label to send back to zero RN16, ifthere are multiple tags random number is zero , but not correctly decoded , itis strategically retransmission Q word or a combination of the first command ,the tag group to be selected , until it can be correctly decoded .
Q12: tag identification number (TID) shouldbe unique you ? How to reach ?
A: tag identification number TID(Tagidentifier) ??is a sign of the difference between the labels identity (analogous to the ticket number ) . From the safety and security point of view,should not be any two identical G2 label , the label should be unique ; Q1answers from the above , we know that the label four memory blocks each use,and some can always be rewritten after the factory only TID ??should also becapable of doing , so the label TID should be unique.
Factory G2 chip manufacturers should usethe Lock command or other means acting on the TID, making it permanently locked; and the manufacturer or relevant organizations should ensure that the appropriatelength for each TID G2 chip is unique in any case there will be no first twosame TID, even if a label is Killed G2 status will not be activated beforeusing its TID ( still this tab ) will not appear on another G2 label.
Such as TID is unique, although the labelEPC codes can be copied to another tab up , but also through the label todistinguish between TID and thus get to the root . Such a framework andmethodology is simple and feasible , but be careful to ensure uniqueness of thelogic chain .
V109 version of the G2 protocol TIDprovisions required only 32-bit ( including 8-bitallocationclassidentifier,12-bittagmask-designeridentifier ,12-bittagmodelnumber); need for more bitsbit, such as SNR (serialnumber serial number ) , said is "Tagsmaycontain",rather than "should". However, EPC numbers are designed to be used onsingle items distinguish ,32-bit is probably not enough, should have SNR. G2protocol amendments or Class2 will consider these and other bars .
Q13: G2 agreement inactivated (Kill)command effect how ? Can re- use has been inactivated label ?
A: G2 protocol sets the Kill command , anduse 32-bit passwords to control and effectively use the Kill command tag willnever generate a modulated signal to activate the RF field , therebypermanently disabled. But the original data may still label , if you want toread them is not entirely impossible , consider improving the Kill commandmeaning - with erasing the data. Really the case , then people should becompletely at ease .
In addition, in a period of time , the costof using the G2 label or other reasons, will take into account both labels canbe recycled reusable condition ( such as the user wants to use tabbed revolvingtrays, boxes , the contents of the corresponding replacement EPC number , UserDistrict contents to rewrite ; replace or re -mount tags costly , inconvenient; etc. ) , you need to be permanently locked even if the labels can also berewritten command, because the impact of different locking state , or onlyWrite BlockWrite, BlockErase order, not necessarily rewrite EPC number , Usercontent or Password ( if the tag's EPC number is locked and thus can not berewritten, or not locked but forgot the label AccessPassword and not to rewriteEPC number ) . This gives rise to a demand that requires a straightforwardErase command - in addition to TID District and Lock Status bit ( TID label cannot be rewritten after the factory ) , other EPC numbers , Reserved Area , UserContent and other areas Lock status bit , even permanently locked , and willall be erased to prepare for rewriting.
By comparison , improved and increased Killcommand Erase command functions the same ( including should use KillPassword),the only difference is that the former does not produce the Kill command so themodulation signal , so you can return to the unity brought about by the Killcommand different parameters RFU value to consider.
Q14: G2 access (Access) and other commandsare optional , if the label or reader does not support optional commands how todo ?
A: If you do not support BlockWrite orBlockErase command can fully Write command ( write once 16-bit) instead of morethan a few times , because the erasure can be considered a write 0 , the formerblock write, block erase block is several times 16-bit, others using similarconditions .
If you do not support Access command , onlyAccessPassword to 0, before entering the Secured state to use the Lock command.In the Open or Secured state where you can change AccessPassword, and then usethe Lock command locks or permanently locked AccessPassword words(pwd-read/write bit is 1, permalock bit is 0 or 1 , the reference schedule ) ,the label never not enter Secured state , and also no longer use the Lock commandto change the status of any locks .
If support for Access command , it may usethe appropriate command to enter all the various states of freedom , inaddition to the label is permanently locked or not locked permanently refusedto execute certain commands and is Killed outside the state , but also moreeffective implementation of the various commands.
G2 agreement provides for an Access Orderis optional Optional , but in the future if we let Access command ormanufacturers become essential for G2 tag and reader support Access command ,then it will control and use more flexible and comprehensive.
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