How is data stored on a RAIN RFID tag?

Modified on Wed, 13 Nov at 12:36 AM

The physical memory of RAIN RFID tags is divided into 4 different logical memory banks. Each of these memory banks is devoted to carry different kind of information.

Reserved memory (MB 00) contains two 32-bit passwords.

The first of these passwords is the Kill password for the KILL command, defined in the GS1 Gen2 standard. The KILL command renders a tag permanently silent. A "killed" tag will not respond to any subsequent commands. In order to avoid any misuse of this KILL command, it is password-protected.

The second of these passwords is the Access password, which allows the tag to be set in either the Open or Secured state. This, for example, can be used to protect data encoded in other memory banks.

EPC memory (MB 01) contains the Electronic Product Code (EPC), which uniquely identifies the object to which the tag is or will be attached. GS1's EPC Tag Data Standard (TDS) normatively specifies coding schemes for EPCs corresponding to various GS1 keys (e.g, SGTIN, SSCC, GIAI, GRAI, etc). Encoding and overwrite protection are the responsibility of the user.

TID memory (MB 10) contains an 8-bit ISO/IEC 15963 allocation class identifier of E2h at memory locations 00h to 07h. TID memory above location 07h SHALL be configured as follows:

■ 08h: XTID (X) indicator (whether a Tag implements Extended Tag Identification, XTID)

■ 09h: Security (S) indicator (whether a Tag supports the Authenticate and/or Challenge commands)

■ 0Ah: File (F) indicator (whether a Tag supports the FileOpen command)

■ 0Bh to 13h: a 9-bit mask-designer identifier (MDID) available from GS1

■ 14h to 1Fh: a 12-bit, Tag-manufacturer-defined Tag Model Number (TMN)

■ above 1Fh: as defined in section 16.2 of TDS

The Tag model number (TMN) may be assigned any value by the holder of a given MDID. However, TID memory locations above 07h shall be defined according to the registration authority defined by this class identifier value and shall contain, at a minimum, sufficient identifying information for an Interrogator to uniquely identify the custom commands and/or optional features that a Tag supports. For the allocation class identifier of E2h this information is the MDID and TMN, regardless of whether the extended TID is present or not. If two tags differ in custom commands and/or optional features, they must be assigned different MDID/TMN combinations. In particular, if two tags contain an extended TID and the values in their respective extended TIDs differ in any value other than the value of the serial number, they must be assigned a different MDID/TMN combination. (The serial number by definition must be different for any two tags having the same MDID and TMN, so that the Serialised Tag Identification specified in Section 16.2.6 is globally unique.) For tags that do not contain an extended TID, it should be possible in principle to use the MDID and TMN to look up the same information that would be encoded in the extended TID were it actually present on the tag, and so again a different MDID/TMN combination must be used if two tags differ in the capabilities as they would be described by the extended TID, were it actually present.

TID memory locations 00h to 1Fh SHALL be permalocked at time of manufacture. If the Tag implements an XTID then the entire XTID SHALL also be permalocked at time of manufacture.

As of Gen2v3, tags with allocation class identifier E2h SHALL support a serialised TID by using a unique serial number, as defined in section 16.2.2 of TDS.

User memory (MB 11), if present, provides optional storage for additonal information regarding the tagged item. When a tag implements user memory then additional information can be stored. TDS specifies the encoding of additional information based on GS1 Application Identifiers.