25 July 1996
Micro-reader Module
2
.
Product Function
2.1 Description
The Micro-reader module is an intelligent plug-in module which can be plugged into or soldered
onto an application specific adapter board. It supports serial data communications between a PC and
TIRIS transponders. With its Serial Communications Interface (SCI) the Micro-reader supports
TTL data communications, which with the addition of a communications driver (for example: RS232
or RS422) allows communication to a standard interface. The Micro-reader can be controlled
remotely by either providing certain inputs with the corresponding voltage level or sending
commands to the SCI. It can be driven either with or without synchronization - the synchronization
can be either wireless or wired to enable reliable operation in multi-reader environments. Two
outputs show the reader status and inform the user about a successful command execution. The
Micro-reader supports all available TIRIS transponders.
2.1.1 Power Supply
There are two separate 5V supplies to the Micro-reader, one for the output stage (VSP) and the
other for the logic (VSL). On power up VSL should rise faster than 0.1 V/ms to ensure a reliable
operation. The Micro-reader has an on-board reset circuit which will reset it should the supply fall
below 4 V (± 0.2 V).
In order to avoid problems with noise conducted via the supply lines, we recommend that if a single
supply is used, separate connections from a common de-coupling capacitor are used to feed the
Micro-reader.
Note
:
The RF Module must not be supplied by Switched Mode Power Supplies (SMPS)
.
This is
because most SMPS operate at frequencies around 50 kHz
.
The harmonics of the
generated field can interfere with the TIRIS receiver
.
Therefore only use linear regulated
power supplies, or SMPS with a
fundamental operating frequency of 200 kHz or higher
.
2.1.2 Antenna
The Micro-reader has been designed for use with a 47
µ
H antenna with a Q of 10 to 20 at 132 kHz
to generate the exciter frequency of 134.2 kHz. Because of the low Q the system does not need to
be tuned.
WARNING
Care must be taken when handling the Micro-reader as high voltages across the antenna pins
could be harmful to your health.
