ib technology
The MicroRWD is essentially a proximity system and a Read/Write range of up to 20cm
can be achieved with the same level of reliable communication and EMC resilience. The
unique AST (Adaptive Sampling) feature allows the RWD to continually adjust and re-
tune the sampling to allow for inductive changes in the RF field, an essential feature for
real-world reliability and robust operation. The communication protocol with the tags
can achieve 4k bits/second of data transfer and the total time to read a 32-bit page takes
less than 50ms.
The MicroRWD can be easily integrated into almost any application; when power (5v
DC) is first applied to the board the red and green LEDs flash once to indicate successful
power-up. The device can also check for broken or shorted antenna and can even detect
badly tuned antennas; these problems are indicated by the red LED flashing
continuously until the fault has been rectified.
The MicroRWD will normally have the red LED lit until a valid card or tag is brought
into the RF field. If the tag is accepted as valid then the green LED is lit and the output
drivers (OP0, OP1, OP2, OP3) are switched on. These outputs can be connected together
to give up to 100ma of drive current for operating a relay etc. In addition, a switch input
is provided for overriding the tag reading operation and switching the output drives
directly.
(Hitag 2 is a trademark of Philips/NXP Semiconductors NV)
The Micro RWD has two basic modes of operation:-
Micro RWD
Chip Module
Micro RWD
Chip Module
Standalone mode with
Internal EEPROM holding
authorised tag codes for
acceptance
RS232
Serial
Antenna
Antenna
comms
Host System
Remote mode (connected to a host computer or microcontroller) and Standalone mode.
1) Remote mode involves connecting to a host serial interface. This is where the
stored list of authorised identity codes can be empty, effectively authorising any
HT2 transponder for subsequent read/write operations. A simple serial protocol
allows a host system to communicate with the Micro RWD in order to program
new authorised identity codes, change passwords and perform read/write
operations to the tag itself.
2) Standalone mode is where the HT2 tag identity codes (serial number) are
checked against a stored list of authorised codes. If an identity code is matched,
the output drives and Green LED are enabled. Effectively standalone mode
occurs when there is no host system communicating with the Micro RWD.
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