EM4056
Continue command
After receiving the BitVal frame from the different transponders in the field the reader decides whether the tags with « 0 » or
« 1 » should continue the arbitration process and communicates this with the Continue frame. The transponders whose last
BitVal was not identical with the confirmation in the Continue frame stop the arbitration process and wait for a new
command.
Arbitration in progress
1 bit
2 bits
MSB
Continue
1 bit
2 bits
MSB
Start Continue
Reader
Start
6 bits
Bit0 Bit0 X X Bit1 Bit1
nth BitVal
6 bits
Bit0 Bit0 X X Bit1 Bit1
n+1th BitVal
Transponder
ta1p
ta2p
ta1p
Fig. 19
When the Continue frame of the 32nd bit is processed, only one transponder is left. This new identified tag sets the RdEn bit
to 1 and belongs no longer to the active group. The arbitration cycle is completed by a transponder frame for selective
commands (RdEn,CRC). The CRC is calculated like a transponder frame for general commands. This means the CRC is
calculated over ROM and RdEn of the transponder in order to increase the reliability of the arbitration.
End of arbitration
1 bit
2 bits
MSB
Continue
1 bit
2 bits
MSB
Start Continue
Reader
Start
6 bits
Bit0 Bit0 X X Bit1 Bit1
32th BitVal
8 bits
MSB
CRC
Transponder
ta1p
ta2p
ta1p
Fig. 20
To identify the address of a transponder, it takes 115 ms (including overhead as mentioned before). That makes it possible
to detect about 8.7 new transponders per second, independent of the number of transponders in the electromagnetic field.
11
www.emmicroelectronic.com
Copyright © 2005, EM Microelectronic-Marin SA
EMMICRO [ EM MICROELECTRONIC - MARIN SA ]
