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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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EM4223  
10. COLLISION ARBITRATION  
2. The Reader detects a collision between two or more  
Transponder replies. Collisions may be detected  
either as contention from the multiple transmissions  
or by detecting an invalid CRC. After waiting until the  
channel is clear, the Reader sends a Close_Slot  
command to increment the Transponder slot  
counter.  
The EM4223 implements the ISO 18000-6 Type A anti-  
collision scheme as described in CD ISO-IEC 18000 part  
6 Type A. Additionally, the EM4223 implements the Fast  
Supertaganti-collision protocol.  
The basic collision arbitration scheme is based on slots.  
The ISO implementation uses regimented slots that are  
controlled by the Reader. Fast Supertaguses pseudo-  
slots (non-synchronised slots) by virtue of the fact that  
transmissions are initiated in integer multiples of a slot  
time. However because Transponder clocks will not be  
identical and because the Reader does not synchronize  
slots at the start of each slot, there will be a natural drift  
and the timing of slots between individual Transponders  
will diverge.  
3. The Reader receives a Transponder Reply without  
error, i.e. with a valid CRC. The Reader sends a  
Next_slot  
command  
synchronized  
to  
the  
Transponder timing window, containing the  
signature of the Transponder just received.  
When Transponders in the ROUND_ACTIVE state that  
have not transmitted in the current slot receive a  
Next_slot command or a Close_Slot command, they  
increment their slot counters by one. When the slot  
counter equals the slot number previously selected by  
the Transponder, the Transponder transmits according to  
the rules above otherwise the Transponder waits for  
another command.  
Refer to the state diagram, Fig. 19.  
General explanation of the collision arbitration  
mechanism  
The collision arbitration uses a mechanism, which  
allocates Transponder transmissions into rounds and  
slots. A round consists of a number of slots. A  
Transponder will only transmit once in a round unless the  
Transponder is in ISO mode and the WUS bit= 0, in  
which case the Transponder will reply in the first slot as  
well as in its chosen slot, or only in the first slot if the first  
slot was selected as the Reply slot by the Transponder.  
The time position where it transmits in a round is  
determined randomly.  
The Reader keeps track of the slot count each time it  
issues a Next_slot command or Close_Slot command.  
When the number of slots used equals the round_size  
issued in the Init_round command, the round has  
completed and the Reader may issue a round initializing  
command. (Note: A Reader may issue a round initializing  
command at any time).  
Transponders that have not been acknowledged (by a  
synchronous Next_Slot command with a valid signature)  
during the current round, will enter a new round on  
determining the end of the current round or at any time  
ISO COMPLIANT SYSTEMS  
on receiving  
a
round initializing command. The  
Each slot has a duration at least as long as a  
Transponder transmission or as long as the Reader  
requires to identify an unproductive (empty) slot and  
send the CLOSE_SLOT command to the Transponder  
population. The Reader determines the duration of the  
slot by closing slots with CLOSE_SLOT or NEXT_SLOT  
commands in response to successful data replies from  
Transponders or clashing replies from Transponders or  
in response to identifying an empty slot.  
Transponders will select a slot at random and transmit in  
the new round when the slot counter value and the slot  
selected are equal.  
If at any time the Transponder receives a wake_up (FST)  
command whether in the READY state or in the ISO  
ROUND_ACTIVE or ROUND_STANDBY states, it will  
immediately switch to the FST mode of operation.  
On receiving an Init_round command, Transponders  
randomly select a slot in which to respond. If a  
Transponder has selected the first slot it will transmit its  
Reply. The Transponder includes its four-bit  
Transponder signature in its Reply. If the Transponder  
has selected a slot number greater than one, it will retain  
its slot number and wait for a further command.  
FST SYSTEMS  
In the absence of an RF field, the Transponders are in  
the RF_field_off state. When the Transponders enter the  
energizing field of a Reader, they go through a power on  
reset sequence. If the FST bit = 0 and the WUS bit = 0,  
then the Transponder moves to the ROUND_ACTIVE  
State it is therefore in a Tag Talks First mode and  
commences  
a Fast Supertagcollision arbitration  
After the Reader has sent the Init_round command there  
are three possible outcomes:  
sequence. If the FST bit = 0 and the WUS bit = 1, then  
the Transponder moves to the ROUND_STANDBY state  
until it receives a Next_Slot, Close_Slot, New_Round or  
Wake_up_FST command, at which time it commences a  
Fast Supertagcollision arbitration sequence.  
1. The Reader does not receive a Reply because  
either no Transponder has selected slot one or the  
Reader has not detected a Transponder Reply. The  
Reader then issues a Close_Slot command because  
it has not received a Reply.  
25  
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Copyright © 2005, EM Microelectronic-Marin SA  
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