User's Manual

PT30 Postal Tag RFID-LSCAN
Page: 4 of 6
3.1 Modes of operation
Postag PT30 has several main modes of operation: sleep, LF excitation recognition, UHF transmission and programming. The
sleep mode is the normal mode of operation.
In the sleep mode, only the LF receiver is powered up and the total current consumption is less than 5uA. When a LF signal is
detected by the LF receiver, it wakes-up the microcontroller to check if this signal has a valid modulation pattern. The LF field
validation is done by the microcontroller using an RC internal 90 kHz clock at a low current consumption. If a valid excitation
field is recognized, then the microcontroller wakes-up its UHF Transmitter and transmits on the UHF the pre-programmed
messages. When PT30 recognizes a valid S21 / S23 excitation it transmits on UHF messages using S21 format. The PT30
operation and the message content can be programmed using dedicated devices.
The tag transmits a number of messages each time it enters a valid S21 or S23 fields. First transmission is delayed a few ms
depending of the parameter WID that programmed randomly for each tag within the 10 -30 range during the manufacturing
process. Subsequent transmissions are each randomly delayed compared with the preceding one based on a calculation that
involves several random numbers generated internally function of another parameter WSD. This WSD parameter is also
programmed randomly for each tag within the 10 -30 range during the manufacturing process. Repeating the same message a
number of times ensures that, even if multiple tags are excited in the same time, many messages will not collide and at least one
from each tag will be successfully received.
3.2 Valid Excitation Fields
For a field to be valid, it has to have a special pattern called exciter ID. If fields with different exciter ID overlap and a tag moves
from one to another it will transmit WEP number of messages each time it “sees” a new exciter ID.
3.3 Commands and Parameters
The commands and parameters accepted by Postag PT30 are the same as for the Postag PT21 / PT23 and are listed in the RFID
System S21 – Reference Guide, document 950061 rev. 1.
The most used programmable parameters for PT30 are WIP, WRC and WUD. Examples of default parameters’ values that will
fit most applications are:
WUD = “xxxxx” 5 characters of user data
WIP, WRC= their sum represents the number of identical messages to transmit following an excitation. WIP
parameter range is 1 to 20, WRC parameter range is 0 to 10, and default values for each are 10.
WID = randomly assigned initial delay after excitation, multiples of 4 ms, range 1-200, default 1. This
ensures a randomization of the first transmissions following an (almost) simultaneously excitation of multiple tags.
WSD = inter-message random delay, range 7 – 15, default 10 (no direct physical interpretation of this value)
3.4 PT23 / PT30 vs. PT21
The main functional differences between tags model PT23 / PT30 and PT21 are related to the ExId range of identifiers and the
black-out time.
3.4.1 ExId range
Postags PT21 recognize and report received ExId with S21 format in the range 0 to 31.
Postags PT23 / PT30 recognize and report received ExId with S21 format in the range 0 to 31, and with S23 format in the range
0 to 127.
3.4.2 Black-out
Black-out is the minimum time interval between two consecutive excitations which the tag can recognize. Postag PT21 has a
black-out time 10.0 s. For PT23 and PT30 this blackout time was reduced to less than 2.0 s. In situations where we want to re-
register a tag that leaves and re-enters a field with the same exciter ID, the tag has to be out of the field for more than the black
out time duration. This happens for example when you try to excite a tag multiple times using the same exciter, like a Universal