ib technology

2

As with the individual MicroRWD versions, the RWD “QT” 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 up to 4k bits/second of data transfer

and the total time, for example, to read a Hitag 2 four-byte page, including reading of the

serial number, selecting the tag and the read operation itself takes less than 100ms.

The MicroRWD can be easily integrated into almost any application; when power (5v DC) is

first applied to the module the red and green LED outputs “flash” once to indicate successful

power-up. The device can also check for broken or shorted antenna and can even detect very

badly tuned antennas, these problems are indicated by the red LED output “flashing”

continuously until the fault has been rectified.

The MicroRWD will normally have the red LED output ON until a valid card or tag is

brought into the RF field. If the tag is accepted as valid then the green LED output is turned

ON (Red OFF) 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.

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 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 internal parameters and perform read/write operations to the tag itself.

2) Standalone mode is where the tag identity codes are checked against a stored list of

authorised codes. If an identity code is matched, the output drives and Green LED are

enabled. In this case the four byte identity code is taken as the transponder serial

number (Page 0) for Hitag 1/S and Hitag 2 or memory bytes 1 - 4 on read-only types,

ignoring the most significant first byte (byte 0). 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