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EM4223V2WS11 参数 Datasheet PDF下载

EM4223V2WS11图片预览
型号: EM4223V2WS11
PDF下载: 下载PDF文件 查看货源
内容描述: 只读超高频射频识别设备 [Read-only UHF Radio Frequency Identification Device]
分类和应用: 射频
文件页数/大小: 29 页 / 426 K
品牌: EMMICRO [ EM MICROELECTRONIC - MARIN SA ]
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R
EM4223  
Because only transponders of interest to the application  
will be selected any other Transponders in the Reader  
field will not degrade Reader performance by needing to  
be read and acknowledge to send them to the QUIET  
state – they virtually do not exist if they have not been  
selected.  
8. TRANSPONDER SELECTION OPERATION  
– INIT_ROUND AND BEGIN_ROUND  
COMMANDS  
The INIT_ROUND and BEGIN_ROUND commands have  
the ability to move only a selected sub-set of the  
Transponder population from the READY to the  
ROUND_ACTIVE states. Transponders that are already  
in the ROUND_ACTIVE or ROUND_STANDBY states  
will be removed from the active Transponder population  
and moved to the READY state if they do not match the  
selection parameters sent with the INIT_ROUND or  
BEGIN_ROUND command.  
The selection capabilities also allow the Transponder  
population to be “Tree-Walked” allowing fully  
“Deterministic” arbitration of a Transponder population.  
By adding more and more bits to the selection criteria,  
the population can be resolved down to a single  
Transponder. (See the explanatory note below).  
This allows the population to be “thinned”, thus  
increasing  
the  
effective  
read  
rate  
achieved.  
EXPLANATION OF “DETERMINISTIC” OPERATION BASED ON “TREE-WALKING”  
Transponders that use randomly selected reply slots in order to transmit their data to a Reader have a  
very small risk of more than one Transponder selecting the same slot several times, which could mean  
that such tags may not be read before they move out of the active population. This is known as  
“Probabalistic” operation and must be balanced against the many advantages of this mode of operation.  
“Tree Walking” is a method of resolving Transponder populations by effectively issuing a series of “tests”  
or “challenges” in which the Reader would request a response from all tags containing say “0” in the 1st bit  
position of the Transponder data (or in an encrypted version of the data). If the Reader received a non-  
clashing response (only 1 transponder responding) it could request that Transponder to send its full data.  
If the Reader received a clashing response (more than 1 transponder responding) it would know that it  
had identified a productive “branch” and would extend its test by requesting a response from all tags  
containing say “00” in the 1st two bit positions of the Transponder data. It would continue testing and  
requesting responses until it had resolved the entire tag population in this manner. If the Reader received  
no response it would know that it had identified an unproductive “branch” and would temporarily abandon  
further testing for Transponders with “0” in the 1st bit position. The Reader would then test for  
Transponders with “1” in the first bit position. This would continue until all Transponders had been  
identified, or moved out of the Reader’s RF field.  
INIT_ROUND COMMAND SELECTION OPERATION  
(see Fig. 19)  
If the AFI value contained in the INIT_ROUND command  
is 0x00, the Transponders will ignore the parameter in  
the command and all Transponders will move to the  
ROUND_ACTIVE state from the ROUND_ACTIVE or  
ROUND_STANDBY or READY states. With an AFI  
parameter of 0x00, the command will perform identically  
to an INIT_ROUND_ALL command.  
The INIT_ROUND command contains a single fixed  
length (8 bit) selection parameter. This parameter  
represents the AFI (Application Family Identifier  
according to ISO18000-6A) value which will be matched  
with the AFI value contained in the Transponders  
memory. Transponders with a matching AFI value will  
move from the ROUND_ACTIVE or ROUND_STANDBY  
or READY states to the ROUND_ACTIVE state and  
commence participation in the Arbitration process.  
Transponders that do not match the AFI value sent in the  
command will remain in the READY state or they will  
move to the READY state if they are already in the  
ROUND_ACTIVE or ROUND_STANDBY states.  
Tags in the QUIET state will ignore the INIT_ROUND  
command.  
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