Why Am I Unable to Block Write Effectively?

By RFID Journal

  • TAGS
Ask The ExpertsWhy Am I Unable to Block Write Effectively?
RFID Journal Staff asked 11 years ago

Do you have any suggestions for a reader-writer that can perform a proper Block Write command instead of writing only two words at a time?

—Name withheld


To answer your question, I reached out to a few people. One is Ken Traub, a consultant with a great deal of knowledge about the EPC Gen 2 RFID standards. Ken says the Gen 2 air-interface protocol standard "has two commands for writing data to the tag. The Write command writes a single 16-bit word. To write more than one word, the reader has to issue this command multiple times. The Block Write command can write any number of 16-bit words. The advantage is that there is less back-and-forth with the tag, so it takes less time. The disadvantage is that the Block Write command does not encrypt the data over the air, so it's more vulnerable to snooping. Also, if the command breaks halfway through, it's hard to know whether part of the tag was written or not. The Block Write command is optional, so not all readers and not all tags support it."

I also reached out to Mark Brown, the senior RFID solution architecture manager of Fujitsu America's New Solution Business division. Mark says most readers support the Block Write command, but the chips also need to support it. "The NXP G2im series of chips, the Impinj Monza 4 series and the Fuitsu tags all support Block Write," he states. "Almost all readers are capable of Block Write. There are exceptions, particularly where a reader is integrated into another device, but generally speaking, if there is a lack of support, it's on the chip side."

In addition, I contacted Sanjv Dua, the president of RFID4U, a leading training company. "Both the reader and the chip need to support Block Write," he says. "Most of the leading readers and chips do support these options. How the user sends the command from a particular reader to a particular chip can make a difference."

If you can let us know what reader and chip you are currently using, we can perhaps better explain why you are unable to Block Write effectively.

—Mark Roberti, Founder and Editor, RFID Journal

Previous Post