TransCore encompass 4, Manual

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Chapter 7 Commands
TransCore Proprietary
7–95
Item 3 Third-most recently acquired ID
Item 4 Fourth-most recently acquired ID
When the uniqueness filter is set to separation of one ID, the newly acquired ID is transmitted only if it is
different from the first item. Separation of two IDs allows transmission if the new ID is different from Items 1
and 2 in the comparison register. Separation of three and four IDs transmit the new ID only if it is different
from the first three and the first four items, respectively.
Note: A new ID can fail the filter test and not be transmitted; however, it remains stored in the
comparison register.
The uniqueness test’s time limit is set by Command
#441.
If an ID is buffered, it will not be accepted
again unless it arrives at the reader more than the programmed time interval from the previous arrival or
until the receipt of one or more other IDs reset the uniqueness.
Reader response:
Done
420N Select Valid ID Code Criteria
See “530 Display RF0 Filter Status” on page 7–109.
Command #420N directs the reader to validate an ID received only after it has been obtained a
specified number of times in sequence. Values for N are 0 through 3 ( Table 23 ). The factory setting is one
acquisition (N = 0).
Table 23 Select Valid Code Commands and Frames
Command Valid Code Frames
4200 1 (factory default)
4201 2
4202 3
4203 4
The validation procedure is executed before the unique ID test (Select Unique ID Code Criteria [#410N]
commands). IDs that do not pass the validation test are not reported.
For example, command
#4203 specifies that the same ID must be obtained from the antenna/RF module
4 times in succession before it is considered for the uniqueness test. This feature is useful in installations
where RF reflections may cause a single tag to be read multiple times or where an occasional ID might be
read from fringe areas.
440 Reset Uniqueness
Command
#440
causes the ID filtering process set by
Select Unique ID Code Criteria
(#410N)
to restart. It is used in conjunction with the
Variable Timeout #44N
commands. This
command provides a method to end all uniqueness timers.