Four memory areas for Gen2 tags The EPC Class 1 Gen 2 tag has four memory areas: Reserved (reserved area, where the password is stored), EPC (where the EPC code is stored), TID (the unique serial number of the chip factory, read-only), and User (user-defined data, optional). Understanding the purpose of these four areas is the basis for designing a coding scheme.
SGTIN-96 encoding format disassembly SGTIN-96 is the most commonly used EPC encoding format, with 96 bits: 8-bit header (00110000 = 0x30), 3-bit filter, 3-bit partition, 40-bit company prefix, 24-bit project reference, 38-bit serial number. The company prefix is applied to GS1, the project reference is determined by the enterprise, and the serial number uniquely identifies the single product. Example: Company prefix 0614141 (7 digits) → partition 5, project reference 100234, serial number 000001, encoding 0x30 5A0E1F2C0 0001A7C8.
User area custom data schemeThe User area is used to store additional data that cannot fit in the EPC code, such as batch number, production date, and shelf life. Common solution: the first 16 digits store the batch number, the next 16 digits store the production date (YYYYMMDD compression), and the last 16 digits store the shelf life days. Note that the size of the User area varies depending on the label model (0-512 bits) and must be confirmed before selection. Writing to the User area will reduce the read and write distance by about 10-15%, which needs to be weighed.
The wonderful use of TID area The TID area stores the chip manufacturer code + model + unique serial number, which is read-only and cannot be changed. It has two key applications: first, anti-counterfeiting verification - reading the TID and comparing it with the database to confirm that the tag is not cloned; second, tag identification - when the EPC area is rewritten, the TID is still the unique fingerprint of the tag. The TID encoding rules of the three major chip series, Impinj Monza, NXP UCODE, and Alien Higgs, are different. You need to consult the corresponding data manual when developing.
Coding scheme design principlesFirst, the EPC area only stores the core identity information to avoid being too long and causing a decrease in reading distance. Second, the User area is used as needed. Information that can be encoded in the EPC area should not be placed in the User area. Third, reserve extension bits to avoid subsequent business changes that require recoding. Fourth, all coding schemes must be documented to avoid inconsistent understanding by different engineers.
