Memory Access

As part of the EPCglobal Class 1 Gen2 RFID Air Interface specification v1.20, the tag memory on Gen2 compliant chips is segmented into four distinct memory banks. This supports operations far beyond just reading the unique TagID (also known as the license plate or EPC #). TagNet supports the ability to parse data from those memory banks to support a variety of use cases. This support is currently available for Motorola XR45x and Impinj R420 Readers. ** Future release will include all LLRP supported Readers.

	Access Memory Bank
	This is enabled by selecting YES or NO from the dropdown. When enabled, the memory bank data will be displayed in the Reader Interrogate list as well as schedule activity logging. Note: enabling this feature incurs a slight additional overhead during the read process and as such will take longer to interrogate the same population of tags.

	Memory Bank
	Enables selection of what memory bank to interrogate. Options are User, TID, EPC and Reserved as described below.

	Payload Start Word
	A ‘Word’ represents 2 bytes or characters. The Payload Start Word is always '0' to signify the beginning of the payload unless you are interested in other start positions in the payload. For example, when retrieving the EPC you will use Payload Start Word of '2' and a Payload Word Count of '6'. As for the User memory payload, a 512-bit will have a Payload Word Count of 32 while a 256-bit will have 16 words.

	Payload Word Count
	Enter the length in Word count to parse from memory bank as described above. Note: If you leave the Payload Word Count blank the RFID tag will respond with the maximum allowable count.

Memory Banks

Listed below is a cursory explanation of each memory bank and its intended use:

1.Reserved (Bank ‘00’) this contains security information and passwords. This varies by Tag manufacturer but typically will have a 32 bit kill password and a 32 bit access password.

An Interrogator may use the kill password to (1) recommission a tag and/or (2) kill a Tag and render it non-responsive thereafter. A Tag shall not execute a recommissioning or kill operation if is kill password is zero. A Tag that does not implement a kill password operates as if it has a zero-valued kill password that is permanently read/write locked.

A Tag with a non-zero access password shall require an interrogator to issue this password before transitioning to the secured state. A Tag that does not implement an access password operates as if it has a zero-valued access password that is permanently read/write locked.

2.EPC (Bank ‘01’) this contains the unique Electronic Product Code (or TagID) commissioned by RFID system. The minimum size is 96 bits but can be up to 480 bits based on Tag Manufacturer.

If using a true EPC following EPCglobal public encoding standards (and using an SGTIN as an example) this is a makeup of the issuing party GLN, product GTIN, and a unique serialization for that given GTIN. As such, any trading partner can ‘decode’ the hexadecimal EPC and derive the above values to support an open supply chain.

If the tag is deployed in a closed loop scenario such as manufacturing or Asset tracking, the EPC represents a unique TagID number also known as a ‘license plate’. This number typically has no meaning other than for the issuing RFID system (such as TagNet).

The EPC is normally assigned during printing of SmartLabels or by a handheld interrogator during tag application.

3.TID (Bank ‘10’) this is ROM based Tag Identification Memory and stores the unique serial number that is factory programmed, locked and cannot be changed. This storage varies by Tag manufacturer but can be up to 64 bits.

This is typically used to ensure the authenticity of a given tag and weed out counterfeit EPC’s by comparing the EPC with the stored TID (captured during commissioning). If the TID does not match the EPC during a read event this would suggest that another computer replicated the EPC.

4.User (Bank ‘11’) this contains a storage area where user information can be written and read. This can be up to 512 bits today but future chipsets will allow more storage such as 1024 bits.

Typical applications for user memory are exchanging transactional information between trading partners such as PO or ASN data as well as Lot# and expiry dates that are not encoded in the EPC.

Tag Memory examples

Shown below are examples of tag interrogations done with various memory bank options and parsing positions selected.

1.Reserved this contains security information and passwords. This varies by Tag manufacturer but typically will have a 32 bit kill password and a 32 bit access password.

Tag ID:
300833B2DDD9048035050000
48.0.2.0867360217.018.889520128
Tag Type: EPC-GEN2
Antenna: 2 - Hallway

Memory Bank: Reserved [1,8]
Payload:
0000000000000000

1.EPC this contains the unique TagID commissioned. Example below with start Word=2 and Word count=6

Tag ID:
300833B2DDD9048035050000
48.0.2.0867360217.018.889520128
Tag Type: EPC-GEN2
Antenna: 2 - Hallway

Memory Bank: EPC [5,12]
Payload:
3000300833B2DDD9048035050000

1.TID this is ROM-based Tag Identification memory and stores the unique serial number that is factory programmed, locked and cannot be changed. This varies by Tag manufacturer but can be up to 64 bits… so then max Word count would = 4 (8 bytes)

Tag ID:
300833B2DDD9048035050000
48.0.2.0867360217.018.889520128
Tag Type: EPC-GEN2
Antenna: 2 - Hallway

Memory Bank: TID [1,4]
Payload:
E2001071

1.User this contains a storage area where user information can be written and read. This can be up to 512 bits so that max Word count would = 32 (64 bytes)

Tag ID:
C29800000000000000001501
Tag Type: EPC-GEN2
Antenna: 2 - Hallway

Memory Bank: User [1,64]
Payload:
Castor for Shelf unit - Titanium