Setup Guide

"T" – Initiate INVENTORY
"T" – Initiate INVENTORY
T
T<MODE>[<LOOPCOUNT>]
Attempt to read tags using the current settings.
The “T” command
The T command performs a full dual-nested
loop sequence of: SELECT / QUERY / ACK /
REQRN / ACK / XREAD / XWRITE, reporting
tags as they are found, performing XDATA
operations, and attempting to force found
tags into the opposite A/B state. All aspects
of this command are controlled by the
reader's global inventory control parameters
(see the “I” command), and the X data
descriptor parameters (see the “X”
command).
The parameters of the SELECT sequence sent
in each OUTERLOOP are fully controllable
through the mask commands (see the “M”
command). Inclusion, exclusion, choice of
A→B, B→A, etc. are all under user control.
The global parameters OUTERLOOP,
INNERLOOP, SELECTLOOP, and Q can be
over-ridden at the command line entry of the
command, all other parameters are set
globally through the I and X series
commands. The T command will start at the
requested Q value, but it will adjust Q
depending on whether there are not enough tag responses (Q will be adjusted down) or too
many response collisions (Q will be adjusted up).
If an OUTERLOOP value is set to 0xFF, then the T command will loop constantly until a
character is received on the interface port. The same thing will occur on a T(n) with a loop
value of 0xFF (equivalent to no loop value given).
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The ISO-18000-6-C (Gen2) protocol specifies a set
of low-level commands that can be used to read and
write RFID tags. In practice, much of the detail
surrounding how this is done is not important to the end
user of an RFID system – you just care if the reader
reports all the tags and that the data you want to write
to them gets written correctly.
That said, some knowledge of what's going on can
be used to optimize a system to improve read
performance, programming reliability and efficiency.
What you want to optimize depends on what you are
trying to do with the RFID tags.
In some cases, you want to read a small number of
tags very quickly and get lots of repeated reads of the
same tag. An example of this might be an application
where you are using an RFID tag on a runner to
determine when he/she crosses the finish line of a race.
The extra reads here are useful for determining the best
“crossing time” for the runner.
In another case, you care less about the number of
redundant reads and more about the number of unique
reads you get. An example might be a tool tracking
application where you are trying to read all the tagged
items within a cabinet and don't want to miss any tags.
To handle these and other cases, you can issue a T
command in conjunction with the M, I and X
commands to fine-tune what is being reported from the
tag field and how the reader interacts with the tag
population it sees.