Alien Technology ALR-8780, Инструкция по интерфейсу

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Acquire vs. Verify
There are two different methods with which to read tags in the field, the Acquire
mode and the Verify mode. Up to now, when this document referred to "reading
tags", it meant "Acquire". When programming is taken into consideration, a
second mode, called "Verify", should be considered.
The reader acquires tags when the "get TagList" command is issued to the
reader, or the reader is reading tags in Autonomous Mode. The actual method
used to acuire the tags in the reader's field is determined by the AcquireMode
setting. This is typically "Inventory" or "Global Scroll". See chapter 3, "Tag
Fundamentals", for more details on the differences between these methods.
Regardless of the actual command issued to read a tag in Acquire mode, the tag
ID returned is always a fully formed ID code, checked against the checksum for
any errors.
This error checking is done by reading the tag ID and calculating its checksum,
then comparing it to the checksum contained within tag memory. If they are
equal, the tag ID is presented to the user. However if a discrepancy occurs
between the checksum and the ID, for example due to a poor air interface
between the tag and reader, then the tag ID is rejected.
Any tag IDs presented to the user by the Acquire commands are therefore
always checked for accuracy.
Note: A tag that is not programmed correctly will not be validated by the
Acquire commands and will be rejected when read.
Note: A tag that has been erased will contain neither a tag ID nor a
checksum. These tags will also be rejected by Acquire commands.
The Verify command is used specifically for interrogating the state of a tag that
may or may not be readable by the Acquire commands.
Verify Tag
9800 | 9780 | 8780 | 9640 | 9774
A Verify Tag command returns the complete tag memory without validating the
tag ID against the checksum. The tag memory returned by the Verify Tag
command is not guaranteed to be correct; it may or may not be valid.
For the Class I tags, the Verify Tag command returns 12 or 16 bytes of memory:
2 bytes of checksum data, followed by 8 or 12 bytes of tag ID (depending on tag
type), followed by Lock and PassCode bytes. Verify is unable to return a value
for a locked tag. (This is to prevent the tag from revealing its PassCode while
locked).
The Verify command returns an error message if the tag is locked.
For the Class BPT tags, the Verify command returns the entire 12 bytes
of tag ID.
A Verify command cannot sort multiple tags; it should only be used on
one tag at a time.