How Does UHF RFID Tag Memory Function?

By RFID Journal

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Ask The ExpertsHow Does UHF RFID Tag Memory Function?
RFID Journal Staff asked 14 years ago

Can you explain the different memory-bank functions of ultrahigh-frequency (UHF) tags? For example, can we perform an inventory by reading only user memory? If not, then how and when could we read it? Also, does a reader interrogate 16 bits of tag memory only at once?

—Name withheld


UHF tags based on the ISO 18000-6C standard can have additional user memory, beyond that required to store an Electronic Product Code (EPC). You do not need user memory to conduct an inventory. Typically, you can take inventory by reading a tag's serial number. User memory can be utilized for a wide variety of applications.

One application is to write information regarding where a product is to be sent. For instance, if you are shipping goods to a distribution center, the DC employees could read the tags' EPCs, and then look up in a database where each case, pallet or tote is to be transported. But if store numbers are written to the products, workers can read the user memory and immediately know, without accessing a database, to which stores the goods are intended to be shipped.

User memory could be used to authenticate goods. A company could write random serial numbers to user memory when pharmaceuticals are produced. When the drugs arrive at a pharmacy, a pharmacist could check with the manufacturer's database to ensure the random serial number matches the correct EPC. IF there is a match, the medicines are legitimate. If there isn't, however, it could mean someone wrote bogus EPCs to tags, and that the goods thus might be illegitimate.

Tego has developed chips that have 32 kilobytes of memory. The tags are designed to store the history of airplane parts. This would provide mechanics, regulators and others with instant access to parts histories, for the purposes of performing maintenance. These special tags do not allow data to be overwritten, thereby ensuring that parts histories can not be doctored.

Readers can interrogate more than 16 bits of memory simultaneously, but not every reader can scan user memory. Usually, you will require special firmware to support some types of user memory.

—Mark Roberti, Editor, RFID Journal

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