ib technology

3

Supported transponder types

The Micro RWD H2 version is designed to communicate with Hitag 2 transponders

configured in PASSWORD mode. Setting the HT2 transponder to any other

configuration will render them inoperable with this system. The operation of the Micro

RWD and Hitag 2 transponders is described in more detail at the end of this document.

The identification codes described in this text are regarded as the first four bytes (serial

number or page 0) of the tag memory array.

Serial Interface

This is a basic implementation of RS232. The Micro RWD does not support buffered

interrupt driven input so it must control a BUSY (CTS) line to inhibit communications

from the host when it is fully occupied with tag communication. It is assumed that the

host (such as a PC) can buffer received data.

Tx, Rx and RTS signals from the Micro RWD are all TTL level and can be converted to

+/-10v RS232 levels using an inverting level converter device such as the MAX202

(note the inversion of the TTL levels).

The serial communication system and protocol allows for a 10ms ‘window’ every Tag

polling cycle indicated by the BUSY line being low. During this ‘window’ the host must

assert the first start bit and start transmitting data. The BUSY goes high again 10ms after

the last stop bit is received. NOTE that only one command sequence is handled at a

time.

b0

b1

b2

b3

b4

b5

b6

b7

b8

b9

5v

0v

idle

START

8 bit data

STOP idle

1

0

TTL levels

5v

0v

5v

0v

5v

0v

RWD

BUSY

RWD

RX

RWD

TX

Ready to Receive

Ready to Receive

RWD cannot receive CMD or DATA

CMD/DATA

CMD/DATA

DATA

RWD tag polling cycle and serial communication BUSY protocol

Transmitted or Received data byte, 9600 baud, 8 bit, 1 stop, No parity (104uS per bit)

Polling delay (100mS to 600mS)

100mS default

Host must Transmit CMD/DATA within 10mS of BUSY going low

Busy