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Class BPT Tags
Class BPT tags from Alien support 96 bits of programmable ID memory. Unlike
the Class I tag, all 96 bits are user-addressable and user-programmable. There
are no prerequisites for the content of this memory space.
EPC Code (or User ID Code)
Byte
0 1 2 3 4 5 6 7 8 9 10 11
Bit
0-7 8-15 16-23 24-31 32-39 40-47 48-55 56-63 64-71 72-79 80-87 88-95
Class BPT Tag Memory Structure
The Class BPT tag does not support Lock or Kill.
Programming Distance & Power Levels
Caution:
It is highly recommended that you read and understand this
section before programming tags.
The term “programming” as used in this manual refers to the operations that alter
the tag memory. These include the Erase Tag, Program Tag, Lock Tag and Kill
Tag commands. These commands are discussed in some detail later in this
chapter. From the operational and software point of view, programming tag IDs is
very simple, in most cases requiring just the click of a button or the issuance of
one command. However, several variables affect programming reliability and
must be properly addressed in every application. There are three factors under
your control to assure programming success in any application: application
software, attenuation, and the physical position of the tags.
Programming Power
Programming a tag requires substantially more power than reading a tag. As a
result, the tag's programming range will be substantially less than its read range.
Programming commands will affect all tags that receive sufficient power to
execute the commands. As a result, the tag to be programmed should be
physically isolated from tags that you do not intend to program. Similarly, you
should program at the minimum power that will reliably program the tag in the
given environment, so as not to affect nearby tags. A lower programming power
requires a shorter physical separation of tags.
The power received by the tag is determined by the power supplied to the
antenna, the distance tag is from the antenna, and the level of signal reflections
from the environment and the object being tagged. Environmental reflections can
cause local power nulls near the tag, and it will not be programmed due to
insufficient power. Tag separation from the antenna should be as constant as
possible, to minimize power variation and to avoid special nulls due to reflection.
Tag orientation with respect to the antenna should also be controlled. In
particular, when using a linear antenna the tag should be presented in the same
orientation as the antenna polarization. The power supplied to the antenna is
controlled by the use of attenuators to reduce the signal strength. The attenuator
value is selected based on careful measurements in the environment after other
variables have been controlled as described above. A variable attenuator is a
useful tool in setting the final attenuation values.
Summary of Contents for ALR-8780
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