Data stored on the tags

Now that we have a better understanding how the communication between the RFID reader and label works, it is time to gain a better understanding how data is stored in the RFID label. There are always four types of memories inside a RFID label, that all have their own purpose and way of working:

EPC memory bank: stores the EPC code and related information.
TID memory bank: stores information on the used chip, and serial number.
User memory bank: optional, can be used to freely store information.
Reserved memory bank: contains the passwords for accessing and killing a label.

EPC memory bank

The EPC memory bank contains the most important information: the EPC code. This can be any string of characters, but preferably it is a code according to the EPC standards. EPCglobal specifies multiple types of codes that can be put in the EPC memory, for retail the SGTIN (Serialized Global Trade Identification Number), GRAI/GIAI (Global Returnable/Individual Asset Identifier) and SGLN (Serialized Global Location Number) are the most important ones.

SGTIN

The SGTIN is an evolution of the GTIN, better known as the EAN or UPC barcodes. Those barcodes contain a Company Prefix (identifying the company that produces a product, for example 'Company XYZ') and an Item Number (identifying the product, for example 'Shoe size 44 color green'). The SGTIN consists of the Company Prefix, the Item Number and a new unique Serial Number. This Serial Number distinguishes one pair of 'Shoe size 44 color green' from another one 'Shoe size 44 color green', and is useful for a lot of applications.

GRAI/GIAI

The GRAI/GIAI identifiers can be used for objects like re-usable packages, transport items or airplane parts. Basically all objects that are not sold in retail stores. They also feature a Company Prefix, Item Reference and Serial Number.

SGLN

The SGLN is basically the same thing: a Company Prefix, with a Location Reference. This can be used to identify locations uniquely.

TID memory bank

In the TID memory bank the manufacturer of the chip (MDID), and the type of the chip (Model Number) is stored. Optionally, a unique serial number for the chip is added, that could be used for Multi-vendor Chip Serialisation - a way to generate serial numbers for the EPC.

User memory bank

The User memory can be used to freely store information. This will typically not be used for fashion retail, but can be used to store expiry dates, etc. etc.

Reserved memory bank

The reserved memory bank contains the passwords:

Access password: to get read or write access to certain memory banks.
Kill password: needed before you can kill the tag.