User Manual

Chapter 8 System Parameters and Comm ands
- 136 - Hi-G-Tek Ltd. Micro electro nic s & A sset Tra cking Techno logy
In this table, each row represents one DataSeal, and each column represents
a windo w. An 'X' in a cell represents that the DataSeal sent its response in
the specified window. Note that there are exactly 4 'X's in each row,
corresponding to Rr. You can see that even though there were some
collisions (in windows 4 and 16), all the 3 DataSeals have at least 1
transmission that does not collide with any other transmission.
In order to achieve high probability to receive all the DataSeals, an
estimation of the maximal number of DataSeals that would respond should
be t aken in account before select ing t he appropriat e values for Nr and Rr.
Fortunately, DataSealLib provides a function that calculates the appropriate
values for Nr an d Rr according to the maximal number of expected
DataSeals. This function is the RFParamete rs.DefaultsFor method.
In fact, the newer DataSeals (versions 3.0 and above), use an improvement
of the Slotted Aloha concept: Whenever the DataReader receives a specific
DataSeal it sends an acknowledge to that DataSeal, causing it to stop
retransmitting its response. This lowers the probability for further collisions
and can shorten the total time of the interrogation by using lower Nr value,
or allow more DataSeals to be received in the same time. T he
RFParameters.DefaultsFor method takes this improvement into account
too.
8.2 DataSeal Parameters
The DataSeal can be configured very flexibly to fit almost any application
requirements. For that purpose it has a set of predefined Parameters that can
be read and/or written. The DataSeal also has some Parameters that are
read-only, either because they are configured in the factory (like the Seal
ID), or because they are status Parameters.
All the Parameters can be read using the Re a d P a rame te rs RF command,
and all the Parameters that are not read only can be written to the DataSeal
using t he Write Parameters RF command. Some Parameters can also be