RFNFC Standards: Type 2 (T2T) vs Type 4 (T4T) Tags
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Introduction : The NFC Forum defines five specific “Tag Types” to ensure interoperability between NFC readers (like smartphones) and passive transponders (tags). Among these, Type 2 and Type 4 are the most widely deployed, but they serve vastly different purposes. Let us understand these tag types and explore differences between them.
NFC Type 2 Tag (T2T)
The Type 2 Tag platform is designed for simplicity and low cost. It is lightweight, efficient and perfect for disposable applications.
- Protocol: It is based on ISO/IEC 14443-3 Type A. Crucially, it does not support the higher level ISO DEP protocol. It communicates using a simple command set directly over the air interface.
- Memory Structure: T2T uses a flat memory model. The memory is divided into Pages (blocks) of 4 bytes each.
- Static Memory: For tags < 64 bytes.
- Dynamic Memory: For larger tags, using a segment management strategy.
- NDEF Handling: To store an NDEF message (like a URL), the tag uses a TLV (Type Length Value) wrapper inside the data blocks. The reader simply looks for a specific “Message TLV” (Tag 0x03) to find the content.
Example Chips :
- NXP NTAG Series
- Mifare Ultralight family
NFC Type 4 Tag (T4T)
The Type 4 Tag is essentially a contactless smart card. It is designed for applications where security, large data capacity and standardized file access are required.
- Protocol: It is based on ISO/IEC 14443-4, supporting the ISO-DEP (Data Exchange Protocol). This layer provides robust error correction and flow control. Physically, it can use either Type A or Type B modulation.
- Memory Structure: Unlike the flat blocks of T2T, T4T uses a File System structure derived from ISO/IEC 7816-4.
- NDEF Application: Data is stored inside a specific “NFC Application” selected by its ID (AID).
- Files: Inside this application, there are distinct files, such as the Capability Container (CC) and the NDEF File.
- NDEF Handling: The reader does not just “scan memory.” It must “Select” the application, “Select” the file, and then issuing “Read Binary” commands.
Example Chips :
- NXP MIFARE DESFire series
- STMicroelectronics ST25TA series
Comparison: T2T vs. T4T
| Feature | Type 2 Tag (T2T) | Type 4 Tag (T4T) |
|---|---|---|
| Underlying Standard | ISO/IEC 14443-3 (Type A) | ISO/IEC 14443-4 (Type A or B) |
| Communication | Proprietary / Simple Commands | ISO-DEP (APDU based) |
| Memory Access | Flat Addressing (Blocks/Pages) | File System (EF, AID) |
| Data Rate | Typically 106 kbit/s | Up to 424 kbit/s (or higher) |
| Max Memory (Typical) | 48 Bytes to 2 KB | 2 KB to 32 KB (up to megabytes) |
| Security | Basic (Lock bits, simple password) | Advanced (AES/DES encryption) |
| Primary Use Case | Smart Posters, URL sharing, Ticketing | Payments, Passports, High security Access |
| Example Chips | NTAG 213, MIFARE Ultralight | MIFARE DESFire EV3, ST25TA |
Conclusion
If your project requires a cheap tag to trigger a URL, launch Wi-Fi pairing or perform basic inventory tracking, Type 2 (T2T) is the correct choice. It is cost efficient and universally supported.
However, if you are building a closed loop payment system, a secure ID badge or need to store large amounts of data reliably, you must use Type 4 (T4T). The added cost provides the necessary cryptographic security and robust communication protocol that T2T lacks.
References for further study
- NFC Forum, “NFC Type 2 Tag Specification” and “NFC Type 4 Tag Specification,” nfc-forum.org
- ISO/IEC, “ISO/IEC 14443-3 and 14443-4 Identification cards — Contactless integrated circuit cards,” iso.org.
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