The ICODE SLIX2 is the newest member of the SLIX family from NXP Semiconductors and the most complete chip of the range: fully backward compatible with the ICODE SLIX, it raises the user memory to 316 bytes and adds an originality signature, a 16-bit counter and flexible memory segmentation. Compliant with the ISO/IEC 15693 standard (known as vicinity) and compatible with the NFC Forum Type 5 format, it targets demanding applications: libraries, pharmaceutical traceability, counterfeit protection, asset and document tracking. It can be read and written by the vast majority of recent NFC smartphones.
Information
| Manufacturer | NXP Semiconductors |
| Family | ICODE (SLIX generation) |
| Reference | SL2S2602 |
| Standard | ISO/IEC 15693 (vicinity cards) |
| NFC Forum type | Type 5 Tag compatible |
| Operating frequency | 13.56 MHz |
| Data rate | Up to 53 kbit/s |
| Unique identifier (UID) | 8 bytes (64 bits), factory programmed |
| Originality signature | 32-byte ECDSA (secp128r1 curve) |
| Operating distance | Up to 1.5 m with a long-range reader; a few centimeters with a smartphone |
| Data retention | 50 years |
| Write endurance | 100,000 cycles |
| Addressable memory (EEPROM) | 320 bytes (2,560 bits) |
| User memory | 316 bytes |
| Counter | 16 bits, in the last block |
Memory
The addressable memory of the ICODE SLIX2 is organized into 80 blocks of 4 bytes: the first 79 form the user memory, the last one is reserved for the counter. A separate, non-addressable configuration area hosts the UID, the passwords, the protections and the originality signature:
| Area | Content | Access |
|---|---|---|
| Configuration area | 64-bit UID, passwords, locks, AFI, EAS, DSFID and originality signature | No direct access; managed through dedicated commands |
| Blocks 0 to 78 | User memory (316 bytes) | Read / write, lockable block by block, segmentable into two protected pages |
| Block 79 | 16-bit counter and its protection indicator | Read; increment and reset through dedicated writes |
In practice, the 316 bytes of user memory can hold an NDEF record containing a URL of around 290 characters, once the Capability Container (written into the first block during formatting) and the NDEF envelope are taken into account, with the common prefix (https://www. for example) compressed into a single byte. It is the largest memory of the SLIX family, with a structure that remains readable by systems designed for the SLIX.
Features & security
- Originality signature: each chip embeds a 32-byte ECDSA signature (secp128r1 curve) computed by NXP over its UID; the Read Signature command makes it possible to verify, even offline with the manufacturer's public key, that the silicon is genuine (an anti-counterfeiting tool unprecedented in the SLIX range).
- Five 32-bit passwords: read, write, privacy, destroy and EAS/AFI, individually lockable; the read and write passwords can be combined into a 64-bit protection, which is enabled irreversibly.
- Flexible segmentation: the user memory is divided into two pages of freely chosen size, each with its own access conditions (public, write-protected or read and write protected; the segmentation pointer is itself lockable).
- 16-bit counter: located in the last block, it is incremented by one with a simple write (protectable by the read password) and reset with the write password, ideal for counting service cycles or uses.
- Privacy and destroy modes: the Enable Privacy command silences the chip (it only responds to the Get Random Number and Set Password commands) until the privacy password is presented, and the Destroy command, protected by a password, disables it permanently and irreversibly.
- EAS, AFI and accelerated inventory: EAS anti-theft feature with selective alarm, AFI filtering (both protectable by password irreversibly) and the persistent quiet mode, which speeds up the inventory of large tag populations by keeping already-censused chips silent.
The ICODE SLIX2 remains a password-based chip: for cryptographic authentication of exchanges, the ICODE DNA family takes over. The chip comes in a single antenna tuning version at 23.5 pF (reference SL2S2602).
Compatibility
The ICODE SLIX2 uses NFC-V technology (ISO/IEC 15693), supported by the vast majority of recent NFC smartphones. On Android, reading and writing work natively with NFC Tools, without any particular restriction. On iPhone, automatic background reading is available from the iPhone XS and XR onwards; models from the iPhone 7 can read and write the chip via NFC Tools on iOS 15.6 or later, by starting the scan manually from the app.
With NFC Tools, the ICODE SLIX2 chip supports reading technical information, writing records, erasing and permanent locking. Configuring the passwords, the segmentation and the counter is done through the chip's dedicated commands. The list of compatible models is available in the article on compatibility.
ICODE SLIX vs ICODE SLIX2
| Chip | User memory | Security | Typical use |
|---|---|---|---|
| ICODE SLIX | 112 bytes | EAS and AFI protectable by password | The versatile label of the range |
| ICODE SLIX2 | 316 bytes | Five passwords, signature, counter, privacy, destroy | The flagship of the SLIX family |
Fully backward compatible with the SLIX, the SLIX2 triples the user memory and concentrates all the features of the generation (read and write passwords, privacy, destroy) while adding the originality signature, the counter and the accelerated inventory. Between the two, the ICODE SLIX-S and SLIX-L cover intermediate needs; beyond, the ICODE DNA family brings cryptographic authentication.
Frequently asked questions
How much data can be stored on an ICODE SLIX2?
The chip has 316 bytes of user memory, which corresponds to a URL of around 290 characters once the Capability Container and the NDEF envelope are taken into account. It is the largest memory of the SLIX family.
What is the difference between ICODE SLIX and ICODE SLIX2?
The SLIX2 triples the user memory, moves from the single EAS/AFI password to five passwords (including memory read and write), and adds the ECDSA originality signature, the 16-bit counter and the persistent quiet mode, while remaining fully backward compatible.
Is the ICODE SLIX2 compatible with iPhones?
Yes. Background reading works from the iPhone XS and XR onwards, and both reading and writing are possible via NFC Tools from the iPhone 7 on iOS 15.6 or later.
Can an ICODE SLIX2 be protected against rewriting?
Yes, in two ways: a permanent, irreversible block-by-block lock, including from NFC Tools, or write protection by password on either of the two segmentation pages, reversible by the password holder.
Useful links
