ib technology

2

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:-

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.

Antenna

Antenna

Micro RWD

Chip Module

Micro RWD

Chip Module

Host System

RS232

Serial

comms

Standalone mode with

Internal EEPROM holding

authorised tag codes for

acceptance