XRA00 Datasheet, PDF (34/40 Pages) STMicroelectronics – UHF, EPCglobal, Contactless Memory IC 96 bit ePC with Inventory and Kill Function

XRA00
Using this information, the Reader may issue a
second PingID command to explore the popula-
tion of XRA00 devices in bin 3, reserving the
XRA00 devices detected in bin 5 for later analysis:
Query 2
[CMD] = 00001000_b(PingID)
[PTR] = 00000000_b(0)
[LEN] = 00000100_b(4)
[VALUE] = 0111_b(7)
This command explores 3 bits farther into the tree
towards the highest memory location from the
memory address containing the bits 0111_b. In Fig-
ure 37., the bold borders show the branches that
contain the XRA00 devices. The two branches
shown in the second half of the drawing contain
groups of XRA00 devices that match Query 2.
These are the same XRA00 devices that respond-
ed to the first query in bin 3.
In this new query, the XRA00 modulation during
the reply interval will take place in bins 1 (response
0010111_b), 6 (response 1100111_b) and 7 (re-
sponse 1110111_b) as shown in Figure 38. and in
bold in Figure 37. The Reader knows 7 address
bits of these XRA00 devices and at least 4 bits of
information concerning the other XRA00 branch
affected by Query 1 but reserved for later analysis.
Although it is not the fastest way to isolate and
identify XRA00 devices, the Reader may continue
with this method and use the PingID command to
follow a branch through the XRA00 ID space until
it has explored the entire XRA00 address and 16-
bit CRC of the XRA00 address.
The recommended way to perform an analysis of
a population of XRA00 devices is to take advan-
tage of the Reader's ability to detect contention in
the reply intervals. The "divide by eight" feature of
the PingID command makes it possible to very
quickly reduce the number of XRA00 devices re-
plying in each bin. Simulations with populations of
100 XRA00 devices show that with random ad-
dresses, an average of less than 4 PingID com-
mands are needed to isolate one XRA00 device. If
only one XRA00 replies in a given bin, the Reader
can decode the 8 bits of information sent from the
XRA00 and issue a ScrollID command to that
XRA00 using the [PTR] [LEN] and [VALUE] data
that successfully isolated the XRA00.
Figure 36. Reader Modulations and XRA00 Backscatter During PingID Reply for Query 1
Reader
Bin
Modulation
Tag Backscatter
000
001
010
011
100
101
110
111
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