What mechanisms are being used to change data values on passive RFID tags?
Data is typically stored in a tag's user memory. This is separate from the field for the unique serial number, which can be preprogrammed or assigned by the user. To answer your question about how data is updated on the tag, I reached out to Sanjiv Dua, the CEO of RFID4U, a leading training company.
Sanjiv says that the air-interface protocol standard (for example, the UHF EPC Gen 2 standard) defines operations, including read-write, and which memory banks or blocks can be written to. "Most reader hardware manufacturers combine these low-level commands with high-level subroutines or DLLs in their software development kits, which can be used by application developers," Sanjiv says. He cites the Google Android NFC library as an example of the development kits available.
—Mark Roberti, Founder and Editor, RFID Journal
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