ANSI/INCITS 256:2007 pdf download.Radio Frequency Identification (RFID).
3 2.45-GHz RFID Protocols
This clause defines the 2.45-GHz RFID commanddata level communication protocols. These protocols facilitate communication between a compliant tag and a compliant interrogator. This clause describes three options: Passive Backscatier. Read.Write Backscatter, and Hybrid Spread RFID System The timing parameters and signal characteristics for the protocols are defined in the physical link specifications in each subclause
3.1 Passive Backscatter RFID System
This portion of the standard describes a passive backscalter RFID system that supports the following system capabilities:
System protocol
Identify and communicate with multiple tags in the field:
– Select a sgroup 04 tags to identify or communicate witt based on information that the user has stored in the tag:
— Read from and write or rewrite data many times to individual tags:
User controlled permanent lock memory:
• Data mtegrity protection
– Manchester bit-wise encoding and CRC•1 6 packet. level protection is applied to the forward link (reader-to-tag) data;
— FMO bit-wise encoding and CRC-16 packet-level protection is applied to the return link (tag-to. reader) data.
In this RFID system, readers power and communicate with the tags mat are within their range. Tags receive data as on-off key amplitude modulation ol the powerdata signal from the reader. During the time that the tag communicates back to the reader, the reader broadcasts a steady radio frequency power level, and the lag modulates the impedance of its radio frequency load attached to the tag antenna terminals. The reader then receives the data from the tag as a variation in a reflection of its transmitted power.
3.1.1 Functional description
This subclause is divided into two subsections:
• Introduction – Provides a general overview of the FHSS backscatter option I RFID system functions
• RFID Tag Command Set — Lists the tag command definitions, both high-level descriptions and the bit patterns assigned to each command
The details of the communication protocol itself, such as start delimiters, preambles, data encoding techniques, and so forth, are discussed in 3.1.2.
3.1.1.1 Introduction
The FHSS backscatter option 1 RFID system includes a base station (interrogator) that runs the FHSS backacatler option 1 RFID protocol, as well as one or more tags. The tag Itself Includes a ch, an antenna tuned to the carrier frequency of the interrogator, and a package to hold the chip and antenna together.
When placed in the radio frequency field of an interrogator, the tag will begin to power up. If the field is strong enough (see 3.1.2). the tag integrated circuit (IC) will execute a power-on reset and be ready to receive commands Each command begins with a preamble and start delimiter. Taken together, the preamble and start delirrWter enable the tag to perform dock and data recovery on the incoming signal. Data to and from the tag is checked for errors using a cyclic redundancy check (CRC); therefore. CRC fields are present in all base station interrogations and In all tag responses. Aoditional data protection is provided by Manchester encoding on the forward (reader-to-tag link) and FMO encoding on the return (tag-to-reader) lmk.
By using the FHSS backscatter option 1 RFID command set. the interrogator can execute a number of Iuncbons on tags in its field. For exarrle, the interrogator can send a command sequence that allows it to identity multiple tags simultaneously in its radio frequency field. Alternately. it can select a subset 04 the tags in the field based on tag memory contents. It also can read data stored on a tag in its field, and write or lock data to such a tag.
31.1.2 RFID tag command set
A command must include, at minrium, the following elements (see Figure 4): reader-to-tag preamble detect field; reader-to-tag preamble: reader-to-tag start delimiter; command field: and CRC-16 field. A command atso can include subsets of the following. depending on the command: tag identihoatlon field; byte mask; address:
byte data; and 8-byte word data Tags can respond to commands, where al responses include a quiet time, a return preamble, CRC-16. and either return data or an acknowledgment code. These fields are descrted Ni detail in 3.1.2.
In the following subclauses, the description of the RFID tag-command set gives details of the command fields arid return data and acknowledgment fields, if any. The subclauses also cover additional high-level elements of the FHSS backscatter option 1 RFID protocol, indung how the rmittiple item identification algorithm works and byte ordering requiements. The more general aspects of the protocol (eg.. prearntles. CRC 16) are covered in detail in 3.1.2.
