Rockwell-automation 56RF RFID System User Manual User Manual download pdf (Page 10)

10 Rockwell Automation Publication 56RF-UM001A-EN-P - October 2011

Chapter 1 Introduction

Power is coupled to the tag by an AC field produced in the transceiver. The

powering field has a frequency of 13.56 MHz and is one of the industrial,

scientific and medical (ISM) frequencies available for worldwide use. When

sufficient power is received by the tag, it is able to respond to commands sent

from the coupler. The coupler sends commands to the card by modulating the

powering field and by using a modulation system known as pulse position

modulation, whereby the position of a single pulse relative to a known reference

point codes the value of a nibble or byte of data. This allows the card to draw the

maximum energy from the field almost continuously. Tags, which have no power

source, can be energized at ranges of up to 3.3 ft (1 m) from a coupler that can

only transmit power within the limits permitted by international radio frequency

(RF) regulations.

A tag only responds when it receives a valid command that selects a single tag

from a possible collection of cards within range of the coupler. This process of

collision detection and selection, also known as anti-collision, is made possible by

detecting the unique identification number encoded into every tag.

Anticollision, and the commands used, are defined in ISO/IEC 15693-3. The

tag responds to the transceiver by drawing more or less power from the field and

generates one or two sub-carriers of around 450 kHz. These are switched on and

off to provide special-encoded data that are then detected by the transceiver.

Backward Compatibility

The Bulletin 56RF RFID system will be offered initially on EtherNet/IP and is

backward compatible with the previous offering of Bul. 56RF ICODE products.

The transceivers and interface blocks are a matched pair so they cannot be

interchanged. However, the tags can be interchanged with either system if they

are ICODE tags. Both systems can read and write these tags seamlessly.

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Rockwell-automation 56RF RFID System User Manual User Manual Page 10