TID Memory

TID Memory

TID (Tag Identification) Memory is one of the four memory banks defined in the EPC Gen2 standard. It contains manufacturer-programmed data that uniquely identifies the tag IC model and, optionally, the individual chip. Unlike EPC Memory, TID is typically read-only — written at the silicon foundry and locked before the chip leaves the wafer.

Memory Structure

The TID memory bank occupies at least 32 bits and follows a standardised format:

The Extended TID (XTID) feature, introduced in Gen2v2, adds a serialised section that gives every physical chip a globally unique identifier. This is a critical capability for tag authentication and anti-counterfeiting because the TID serial cannot be overwritten.

Use Cases

Authentication and anti-cloning: Because TID is factory-locked, an attacker cannot copy it onto a blank tag the way they can copy EPC Memory. Systems that verify TID against a database of known-good serials can detect cloned tags. Combined with crypto suite authentication, TID verification provides strong anti-counterfeiting assurance.

IC identification: During commissioning or quality control, reading the TID tells the host system exactly which chip model is embedded in each inlay. This is useful for verifying that suppliers have used the specified IC (e.g., Impinj Monza vs. NXP UCODE).

Diagnostics: When troubleshooting read failures, the MDID and TMN fields in TID can reveal whether the issue is specific to a particular IC revision. Reader firmware can also use TID data to apply IC-specific optimisations during encoding.

Reading TID

Reading TID requires the reader to issue a Read command targeting memory bank 10b (binary) after singulating the tag. Most readers support TID reads as part of the inventory round configuration — for example, via the LLRP AccessSpec mechanism. Reading TID adds latency to each tag transaction (typically 5-15 ms), so it is usually enabled only when authentication or IC verification is required.

TID vs. EPC for Unique Identity

While EPC provides the logical identity (what product this tag represents), TID provides the physical identity (which silicon chip this is). Combining both enables powerful supply chain integrity checks — verifying that a specific serialised product (SGTIN) is associated with a specific physical chip that has not been swapped or tampered with.